Black-tailed prairie dogs play a number of vital roles in their ecosystem. They modify the vegetational community, aerate the soil, provide food and shelter for a number of predators, and provide homes for a number of parasites. Each of these roles has extensive impact on the ecosystem.
Prairie dogs modify the vegetational community in their habitat in two distinct ways. First, and most conspicuous, the vegetation found within prairie dog colonies is dramatically shorter than the vegetation in surrounding areas. Although C. ludovicianus appears to colonize areas where the vegetation is already short, they still actively modify the landscape after colonizing an area. The short vegetation results from a combination of foraging behavior and active trimming by these rodents. Shorter vegetation seems to benefit the prairie dogs by increasing visibility, and presumably, assisting in detection of predators. Second, through some mechanism as yet unknown, the prairie dogs facilitate the growth of certain plants within their communities. Some of these plants are only rarely found on the prairie outside of prairie dog towns.
As a prey species, black-tailed prairie dogs provide food for other animals, including mammals, snakes, and birds of prey. Since they are primary consumers, they provide a vital link in food webs.
Of special note is the relationship between black-footed ferrets and C. ludovicianus. Black-footed ferrets are highly endangered mammals, the near extinction of which was intimately tied to their reliance on prairie dog colonies for food and shelter. Because of the large scale eradication of C. ludovicianus from rangelands, black-footed ferrets were unable to sustain an effective wild population. Although captive breeding of these ferrets has helped to restore the population, their continued survival depends on the availability of prairie dog colonies in which they can live. Some authors have suggested that predation by ferrets has set black-tailed prairie dogs apart from other species in the genus Cynomys, and may account for the higher levels of coloniality and sociality seen in this species.
One of the costs of coloniality that C. ludovicianus faces is a heightened level of parisitism. Black-tailed prairie dogs harbor numerous fleas, lice, and ticks. In addition to the discomfort that these parasites inflict, they infect the prairie dogs with diseases. For example, fleas transmit bubonic plague causing bacteria (Pasturella pestis). Plague, in addition to threatening the prairie dogs, can be transmitted to humans.
Ecosystem Impact: creates habitat; soil aeration ; keystone species
Communication within C. ludovicianus as been well studied. As might be expected from such a highly social species, means of communication are varied. Black-tailed prairie dogs have 12 distinct calls, including antipredator calls, and the conspicuous "jump-yip", in which an individual stretches to its full height on hind legs, then throws the forefeet into the air as it calls. The jump-yip call of one individual seems to excite other members of the coterie, as well as individuals in adjacent coteries, into producing their own "jump-yip" calls.
In addition to vocal communication, C. ludovicianus employs physical contact (grooming, nuzzeling, playing, fighting), as well as visual signals for communication. Sniffing of other individuals occurs, and implies some chemical communication, especially in the context of mating.
Communication Channels: visual ; tactile ; acoustic ; chemical
Perception Channels: visual ; tactile ; acoustic ; chemical
Historically, prairie dogs were villified by ranchers, and efforts were made to erradicate entire populations. Although not as common as they once were, many prairie dog colonies persist in protected areas.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
As is the case for their positive economic impact on humans, the negative impact of these animals on humans is varied. Cynomys ludovicianus has historically been considered a pest species, although most of the grounds for viewing it as such have been mistaken. Prairie dogs have been known to destroy crops of corn, wheat, alfalfa, hay, sorghum, potatoes and cantaloupes, causing some concern for agriculture. Although they are reported to compete with cattle and sheep for forage, there is actually little dietary overlap with these species. Cynomys ludovicianus burrow systems are alleged to present hazards to cattle and horses, making broken legs a threat. However, there are actually very few leg fractures in domestic livestock attributable to prairie dog burrows. Also, as discussed under "Economic Importance for Humans: Positive", the benefits of C. ludovicianus to the vegetational community may far outweigh the possible threat this species poses to agriculture. Prairie dogs may serve as a reservoir for spotted fever and bubonic plague.
Negative Impacts: injures humans; crop pest
Black-tailed prairie dogs are beneficial to humans in a variety of ways. They may help the vegetation in ways which benefit domestic cattle and horses. Because of their excavation of the soil and clipping of vegetation, as well as their fecal material and urine, many plants receive fertilization and optimal growing conditions. Bison, pronghorn antelope, and domestic livestock prefer for forage at the sites of prairie dog colonies when such are available. Beyond their utility in modifying the vegetation to the liking of livestock, black-tailed prairie dogs have been used in the laboratory for studies of gallstones. Prairie dog towns are popular among sightseers in the American west. In addition, prarie dogs are said to make excellent pets if captured young. Historically, these animals have provided food for native americans.
Positive Impacts: pet trade ; food ; ecotourism ; research and education; produces fertilizer
Black-tailed prairie dogs eat primarily leaves, stems, and roots of grasses, weeds, and forbs. Although vegetable matter comprises over 98% of the diet, animal matter may somteimes be ingested. The animals typically eaten by prairie dogs are grasshoppers, cutworms, bugs, and beetles. Black-tailed prairie dogs do not need to drink water in order to get the moisture they need to survive. They obtain all the moisture they need from their moist, leafy foods. Most prairie dogs forage close to their burrows when possible, moving into distant foraging areas only when forced to do so by local shortages of green shoots.
Cynomys ludovicianus forages selectively from the plants available in its habitat. Diet also varies seasonally. In the summer, black-tailed prairie dogs prefer to feed upon wheatgrass (g. Agopyron), buffalo grass (g. Bromus), grama (g. Bouteloua), rabbitbush (g. Chrusothamnus), and scarlet globmallow. In the winter, they eat prickly pear cactus (g. Opuntia), thistles (g. Cirsium), and various roots.
Animal Foods: insects
Plant Foods: leaves; roots and tubers; wood, bark, or stems; seeds, grains, and nuts; flowers
Primary Diet: herbivore (Folivore )
Cynomys ludovicianus occupies narrow bands of short to mid-grass prairies from central Texas in the south to just north of the Canadian-United States boundary. Historically, the range of black-tailed prairie dogs was greater. They were found from Nebraska in the east to Montana in the west. They ranged from Canada in the north to Mexico in the south. However, intensive efforts at eradication of these animals by ranchers have reduced the species to a few isolated populations associated mainly with protected lands.
Biogeographic Regions: nearctic (Native )
Cynomys ludovicianus occupies a relatively restricted range of open, level, arid, short-grass plains. These prairie dogs are commonly found near river flats or in coulee bottomlands where sagebrush, greasewood, and prickly pear grow. They are never found in moist areas.
Range elevation: 1,300 to 2,000 m.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: savanna or grassland
As is true for most mammals, most black-tailed prairie dogs die young. Only 54% of females and 47% of males who emerge from their natal burrows survive their first year of life. Females can live to be up to eight years old, whereas males don't tend to live longer than 5 years under natural conditions.
Range lifespan
Status: wild: 8 (high) years.
Average lifespan
Status: wild: 1 years.
Average lifespan
Status: captivity: 8.5 years.
Cynomys ludovicianus varies in length between 352 and 415 mm. Sexual dimorphism is prevalent, with males measuring greater in total length than females (male range: 358 to 415 mm; female range: 352-375 mm). Males also tend to be between 10 and 15% heavier than females, weighing in between 850 and 1,675 g, compared to females which weigh between 705 and 1,050 g. Weight varies seasonally, with both males and females reaching their highest weights in the autumn, and lowest weights in winter.
Black-tailed prairie dogs undergo two molts per year, with slightly different pelage coloration in each molt. The general coloration is brownish to brownish-red dorsally, with whitish fur on the ventrum. During the summer, individual hairs are mixed, with some being banded (black at the base, with a whitish band, then a cinnamon band, followed by a subterminal buff band, and a black tip), and some colored either solid black or half black. The latter type of hairs are longer than banded hairs and are interspersed in the coat. In winter, the banded hairs are different, with black at the base, followed by buff, then cinnamon, and possessing a white tip. Females have 8 grayish mammae that are visible only during pregnancy and lactation.
Black-tailed prairie dogs are easily distinguished from Mexican prairie dogs because of non-overlapping geographic ranges. In addition, C. ludovicianus is easily distinguished from members of the subgenus Leucocrossuromys (including Gunnison's prairie dogs, white-tailed prairie dogs, and Utah prairie dogs). In addition to having mainly non-overlapping ranges, members of Leucocrossuromys all hibernate, have white- to gray-tipped tails, have smaller molars, and possess distinctly different territorial and antipredator vocalizations than do black-tailed prairie dogs.
Range mass: 705 to 1,675 g.
Range length: 352 to 415 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: male larger
Average basal metabolic rate: 2.358 W.
Black-tailed prairie dogs fall victim to a variety of predatory species. Terrestrial predators include coyotes, badgers, lynx, black-footed ferrets, rattlesnakes, and bullsnakes. Avian predators include prairie falcons, golden eagles, and a variety of hawks (Accipiter and Buteo).
The greatest defense that C. ludovicianus has against predators is exactly the same thing which makes the species so vulnerable to predators; namely, the number of animals living together in a colony. Because there are so many prairie dogs in a single colony, colonies attract the notice of predators. But, because there are so many prairie dogs present, all scanning their environment periodically, predators are readily detected by these rodents. When a predator is noticed, individual prairie dogs give alarm calls, warning their relatives that danger is near. The prairie dogs can then take shelter immediately in one of the many burrows nearby.
Known Predators:
Anti-predator Adaptations: aposematic
Mating is closely related to social structure in these animals. The typical mating pattern is polygynous, with a single male mating with multiple females in his home coterie. However, in some cases, more than one male may be resident in a single, large coterie. In these cases, females within the coterie may mate with both resident males. In such cases, the first male to copulate with the female sires more offspring than does the second. Additionally, there appears to be some communal nursing of young after the time they appear above ground, qualifying the species for status as a cooperative breeder.
Mating System: polygynous ; polygynandrous (promiscuous) ; cooperative breeder
Reproduction occurs once per year, with the exact timing of mating varying with latitude. In Oklahoma, breeding takes place in January; in Colorado breeding takes place in February. Between late February and March,balck-tailed prairie dogs in South Dakota breed. Finally, those animals residing in the northern portions of the species range breed in late March and early April. Females of this species are typically sexually receptive only one day of the year. Females failing to conceive after this initial estrus sometimes enter estrus a second time about 13 days after their first estrus.
Approximately 98% of matings in C. ludovicianus occur underground. This probably helps to reduce intermale competition for females. Several behaviors are associated with mating both underground and above ground. These include frequent entrance of a breeding male and estrus female into the same burrow; very high frequency of interaction between the male and female; self licking of genitals in both male and female; gathering of nesting materials by males, and transport of those materials into a burrow; and a later than normal nighttime entrance into the burrow by estrus females. In additon, male black-tailed prairie dogs have a unique vocalization that is associated only with mating behaviors.
Gestation ranges in length from 33 to 38 days, with a mean of 34.6 days. Litter sizes ate birth range from 1 to 8 young, with a mean litter size at emergence from the burrow of 3 young. Young are altricial, being born blind, naked, and mostly helpless. Neonates measure approximately 70 mm in length, and weigh an average of 15 g. Fur is evident by the age of 3 weeks, and eyes are open by approximately 5 weeks of age. The age at weaning varies with litter size, as larger litters nurse longer than smaller litters. Lactation lasts from 37 to 51 days, with a mean of 41.3 days. The termination of lactation occurs shortly after emergence from the natal burrow, and after emergence but prior to the end of lactation, pups may nurse from females other than their own mother.
Sexual dimorphism in size is already established by the time juveniles emerge from tehir natal burrows. Males weigh an average of 147 g at emergence and females weigh an average of 141 g. By October, males have acheived an average weight of 556 g, and females an average of 532 g.
Females remain in their natal coterie for life, but males disperse as yearlings. This results in minimization of inbreeding. Also, adult males rarely remain within the same coterie for more than two breeding seasons, thus reducing the possibility that they will mate with their female offspring.
The age of sexual maturity varies. Although most black-tailed prairie dogs copulate for the first time as two-year-olds, some reach maturity earlier or later. Among females, 35% breed as yearlings, 60% breed as two-year-olds, and 5% delay reproduction until they are 3 years old. Males show sexual asymmetry, being less likely than females to breed as yearlings, and more likely than females to dely reproduction until their third year. Among males, 6% breed as yearling, 70% as two-year-olds, and 24% breed in their third year.
Female C. ludovicianus who mate do not always produce litters. Successful reproduction is positively related to female age. Only 54% of yearling females who copulate subsequently give birth, compared to 89% of females over the age of 2 years who copulated. Failure to give birth results from both failure of conception, resorption of embryos, and miscarriage of pregnancies.
Breeding interval: Females of this species are able to breed once per year.
Breeding season: Breeding occurs between January and April, depending upon latitude.
Range number of offspring: 1 to 6.
Average number of offspring: 3.
Range gestation period: 33 to 38 days.
Average gestation period: 34.6 days.
Range weaning age: 27 to 51 days.
Average weaning age: 41.3 days.
Range time to independence: 1 to 2 years.
Average time to independence: 1 years.
Range age at sexual or reproductive maturity (female): 1 to 3 years.
Range age at sexual or reproductive maturity (male): 1 to 3 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization ; viviparous ; oviparous
Average birth mass: 15.75 g.
Average number of offspring: 4.
Cynomys lodovicianus pups are altricial. They require a large investment by parents in order to ensure their survival. Males are not directly involved in caring for young, but help to protect pups within their coteries by defending the coterie against strange males. The bulk of parental care is provided by females, who nurse, groom, and protect their offspring. Because of the prevalance of infanticide in this species, young are very vulnerable prior to emergence from their natal burrows. After emergence from the burrow, however, young are less vulnerable. They eat solid foods primarily, although they continue to nurse for about one week. Interestingly, females in the coterie frequently nurse emergent pups other than their own offspring.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Male, Female); pre-hatching/birth (Provisioning: Female, Protecting: Male, Female); pre-weaning/fledging (Provisioning: Female, Protecting: Male, Female); pre-independence (Protecting: Male, Female); post-independence association with parents; inherits maternal/paternal territory
This taxon can be found in the Colorado Plateau shrublands, as one of its North American ecoregions of occurrence. The Plateau is an elevated, northward-tilted saucer landform, characterized by its high elevation and arid to semi-arid climate. Known for the Grand Canyon, it exhibits dramatic topographic relief through the erosive action of high-gradient, swift-flowing rivers that have downcut and incised the plateau. Approximately 90 percent of the plateau is drained by the Colorado River and its tributaries, notably the lower catchment of the Green River.
A pinyon-juniper zone is extensive, dominated by a pygmy forest of Pinyon pine (Pinus edulis) and several species of juniper (Juniperus spp). Between the trees the ground is sparsely covered by grama, other grasses, herbs, and various shrubs, such as Big sagebrush (Artemisia tridentata) and Alder-leaf cercocarpus (Cercocarpus montanus).
A montane zone extends over large areas on the high plateaus and mountains, but is much smaller than the pinyon-juniper zone. The montane vegetation varies considerably, from Ponderosa pine in the south to Lodgepole pine and Aspen further north. Northern Arizona contains four distinct Douglas-fir habitat types. The lowest zone has arid grasslands but with many bare areas, as well as xeric shrubs and sagebrush. Several species of cacti and yucca are common at low elevations in the south.
Numerous mammalian species are found within the Colorado Plateau shrublands ecoregion, including the Black-tailed prairie dog (Cynomys ludovicianus); Long-eared chipmunk (Tamias quadrimaculatus); Utah prairie dog (Cynomys parvidens EN); Yellow-bellied marmot (Marmota flaviventris); and the Uinta chipmunk (Tamias umbrinus), a burrowing omnivore.
A large number of birds are seen in the ecoregion, with representative taxa: Chestnut-collared longspur (Calcarius ornatus NT); Greater sage grouse (Centrocercus urophasianus NT); Northern pygmy owl (Glaucidium gnoma); Cactus wren (Campylorhynchus brunneicapillus).
There are various snakes occurring within the Colorado Plateau, including: Black-necked garter snake (Thamnophis cyrtopsis), usually found in riparian zones; Plains Blackhead snake (Tantilla nigriceps); Black-tailed rattlesnake (Crotalus molossus), who seeks inactivity refuge in rock crevices, animal burrows and even woodrat houses. Other reptiles found here include the Common checkered whiptail (Cnemidophorus tesselatus).
There are only a limited number of anuran taxa on the Colorado Plateau; in fact, the comprehensive occcurrence list for the ecoregion is: Red-spotted toad (Anaxyrus punctatus); Canyon treefrog (Hyla arenicolor); Woodhouse's toad (Anaxyrus woodhousii); Couch's spadefoot toad (Scaphiopus couchii); Northern leopard frog (Lithobates pipiens); Plains spadefoot toad (Spea bombifrons); and Southwestern toad (Anaxyrus microscaphus). The Tiger salamander (Ambystoma tigrinum) is the sole salamander found on the Colorado Plateau shrublands.
The Colorado River fish fauna display distinctive adaptive radiations. The Humpback chub (Gila cypha), for example, is a highly specialized minnow that lives in the upper Colorado. It adapted to the water’s fast current and its extremes of temperature and flow rate. Dams and water diversion, however, have created a series of placid, stillwater lakes and side streams, and the Humpback chub may not be able to adapt to these altered conditions. The species, along with other native Colorado River fishes including the Bonytail (Gila elegans), Squawfish (Ptychocheilus lucius), and the Flannelmouth sucker (Catostomus latipinnis), may not survive much further in time.
Subterranean burrows created by black-tailed prairie dogs serve as refuges from the external environment and are one of the most important features of black-tailed prairie dog colonies. They are used for breeding, rearing young, and hiding from predators. Burrows are maintained from generation to generation and serve as stabilizers on the physical and social aspects of the colony [75]. Black-tailed prairie dog nests are located underground in burrows and are composed of fine, dried grass. Nest material is collected throughout the year by both sexes and all age classes [69,75]. Tunnel depth of black-tailed prairie dogs in central Oklahoma was typically 4 to 5 feet (50-60 inches) deep [144]. Most black-tailed prairie dog colonies contain 20 to 57 burrows/acre [20,75,81].
There are 3 types of burrow entrances- dome mounds, rimmed crater mounds, and entrances without structures around them. Entrance features may prevent flooding and/or aid in ventilation [69,75,81]. Dome mounds consist of loosely packed subterranean soil spread widely around the entrance of the burrow and tend to be vegetated by prostrate forbs. Rimmed crater mounds are cone-shaped mounds constructed of humus, litter, uprooted vegetation, and mineral soil. Black-tailed prairie dogs compact the soil of these mounds with their noses, creating poor sites for seedling establishment [23]. Rimmed crater mounds may be used as wallowing sites for American bison. Burrow entrances without structures around them are usually located on slopes >10% [75]. The density of black-tailed prairie dog burrow openings depends on both substrate and duration of occupation of an area [81].
Vegetation heights between 3 and 5 inches (7-13 cm) and a slope of 2% to 5% are optimal for detecting predators and facilitating communication amon black-tailed prairie dogs [25,27,37,75,81]. Grazing cattle keep vegetation short in the vicinity of black-tailed prairie dog colonies, reducing susceptibility to black-tailed prairie dog predators and potentially expanding colony size [59,75,81,89]. Black-tailed prairie dogs were rarely seen feeding >16 feet (5 m) from colony edges in Wind Cave National Park [50].
As of 2007, little information is available on HABITAT RELATED FIRE EFFECTS for the black-tailed prairie dog. Despite the lack of information, some generalizations may be possible based on their habitat requirements. Black-tailed prairie dogs inhabit grasslands including short-grass [26,53,70,77,91,99] and mixed-grass prairie [12,23,25,28,36,45,50,71,99], sagebrush steppe [26,79,104,105], and desert grassland [35,38,89] (see Plant Communities). The effects of fire on grasslands vary with plant community, season, weather patterns, and fire characteristics [74,83,137,149]. Information on black-tailed prairie dog ecology in sagebrush steppe and desert grasslands is sparse. The following information is from short- and mixed-grass prairie habitat. For more information on fire regime characteristics of other potential black-tailed prairie dog habitat, see the table below.
The nutrient content of grassland plants in various grassland habitat types around the world is typically higher following fire [34], and herbivores such as deer (Odocoileus spp.) seek postburn areas [138]. Black-tailed prairie dogs may also seek postburn areas for foraging. Due to the prairie dog's reliance on grass for food, low- to medium-severity fires may be beneficial, while high-severity fire may have negative impacts on the black-tailed prairie dog in the short-term.
Prairie: Blue grama, buffalo grass, and western wheatgrass are dominant grasses in shortgrass prairie and are favorite foods of black-tailed prairie dogs (see Food habits) [44,75,81,130]. Fire generally favors blue grama [2,5,41,125], and either favors or has no long-term effect on buffalo grass [143,147] and western wheatgrass [40,42,51,52]. The effects of fire on these 3 grass species vary depending on the phenological stage, season of burning, fire severity, and/or postfire weather conditions [142,148]. For more information about the effects of fire on the 3 grass species favored by black-tailed prairie dogs, see the FEIS reviews for blue grama, buffalo grass, western wheatgrass.
Blue grama [2,5,41,125], buffalo grass [143,147], and western wheatgrass [40,42,51,52] are generally favored by spring burning, which increases their frequency, biomass, and cover [40,42,62,72,76,100,142]. Spring (April) prescribed burning in mixed-grass prairie in Badlands National Park, South Dakota, favored buffalo grass. Buffalo grass began vegetative expansion and produced seed during the first growing season after fire [142]. Gartner and White [51] report that late spring and early summer burns can cause increases or decreases in western wheatgrass during the 1st growing season, but no difference between preburn and control was evident by the 2nd growing season in mixed-grass prairie communities. In the 1st and 2nd growing seasons following a spring burn in Nebraska mixed-grass prairie, blue grama experienced a significant increase (p<0.10) in basal cover on burned plots compared to unburned plots [119]. On sites in South Dakota, blue grama increased from 4% to 11% cover in the 1st growing season following a spring prescribed burn and increased from 12% to 18% cover during the 2nd growing season [41]. Following early spring prescribed burning in Texas, blue grama yield increased up to 400 lbs/acre (452 kg/ha) in the 1st growing season [147].
According to a 1980 review, during years of normal or higher than normal precipitation, timing of vegetational regrowth is quicker [60,135,147]. During dry years, grasses on the shortgrass prairie are harmed by fire [148]. In a buffalo grass-blue grama community in Hays, Kansas, it took vegetation 3 growing seasons to recover following a spring wildfire when the soil was drier than normal [86].
Fire may favor black-tailed prairie dog colony expansion if it removes woody shrubs and other visual obstructions. Prescribed burning during spring followed by mechanical brush removal in Theodore Roosevelt National Park, South Dakota, resulted in colony expansion into treated areas. Three active black-tailed prairie dog colony sites were chosen for the study: Peaceful Valley, 23.1 acres (9.34 ha); Mike Auney, 65.0 acres (26.3 ha); and Johnson's Plateau, 86.7 acres (35.1 ha). Adjacent to each active colony was a 4.9 acre (2.0 ha) treatment unit and a 4.9 acre control unit. The plant community was not described but was probably either shortgrass or mixed-grass prairie. The treatment units were burned in May 2002. The burns were patchy and incomplete, so mechanical brush removal was used to compensate for the incomplete burning. Over a 1.5 year period, black-tailed prairie dogs expanded their colonies into treated plots significantly (P<0.001) more than control plots. In the 3 treatment plots, there was an average of 335 new burrows and a mean 50.3% expansion in area, compared to 69 new burrows and a mean 1.6% expansion in control plots [98]:
Number of new black-tailed prairie dog burrows and area of colony expansion in treatment and control plots [98]
September 2002 (4 mo postfire) September 2003 (16 mo postfire) Burning and mechanical brush removal Control Burning and mechanical brush removal Control New black-tailed prairie dog burrows Peaceful Valley 192 (419)ª 40 (141) 458 (685) 41 (142) Mike Auney 315 (528) 86 (135) 358 (434) 116 (165) Johnson's Plateau 138 (304) 54 (110) 191 (357) 50 (106) mean (± 1 SE) all colonies 215 ± 52.4 60 ± 13.6 335 ± 77.9 69 ± 23.6 Area of expansion (ha) Peaceful Valley 0.89 0 1.56 -0.05 Mike Auney 1.26 0 1.09 0.10 Johnson's Plateau 0.62 0 0.31 -0.05 mean (± 1 SE) all colonies 0.92 ± 0.19 0 0.99 ± 0.36 0.001 ± 0.047 ª Numbers in parentheses are total number of burrows, including burrows present in the active black-tailed prairie dog colony encompassed by plot margins before experimental manipulations in 2002.Moderate amounts of disturbance appeared to increase plant species diversity in a mixed-grass prairie in Comanche County, Oklahoma. Plant species diversity and richness were compared in 7 treatments containing combinations of large scale, low-severity prescribed fires, light grazing by cattle, severe grazing by black-tailed prairie dogs, and wallowing by American bison. Treatments were not replicated, so significance of differences between treatments was not assessed. The 2 sites with the highest plant species diversity and richness were those with combinations of low- to moderate- severity disturbances (see table below). Plant diversity and richness was lowest on undisturbed study sites, sites that were burned frequently, and severely disturbed sites containing black-tailed prairie dogs [28]:
Plant diversity and richness in 7 undisturbed and disturbed mixed-grassland sites [28]
Treatment
Undisturbed area Lightly grazed by cattle Lightly grazed by cattle, American bison wallows Frequent, low-severity prescribed fire Low-severity prescribed fire, lightly grazed by cattle Low-severity prescribed fire, lightly grazed by cattle, American bison wallows Severe grazing by black-tailed prairie dogs DiversityThe following table provides fire regime information on vegetation communities in which black-tailed prairie dogs may occur, based on the habitat characteristics and species composition of communities black-tailed prairie dogs are known to occupy. There is not conclusive evidence that black-tailed prairie dogs occur in all the habitat types listed, and some community types, especially those used rarely, may have been omitted. Find further fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".
Objectives of ecologists and conservationists often conflict with those of ranchers and rural landowners regarding management of black-tailed prairie dogs [126]. Because black-tailed prairie dogs have a strong positive influence on plant and animal diversity in their native habitat, ecologists and conservationists are concerned regarding declines in their populations over the last century (e.g., [88,111]). Conversely, because black-tailed prairie dogs alter plant community structure and composition [12,29,30,71,81], they have often been regarded as competitors with livestock [18] and are subject to eradication and control efforts.
Ecological role and threats: Black-tailed prairie dogs have been called "ecosystem engineers" due to their influence on the biotic and abiotic characteristics of their habitat, landscape architecture, and ecosystem structure and function [21,35,139]. For details on their effects on vegetation and soils, see Site-scale characteristics. Research suggests that black-tailed prairie dogs are a keystone species [21,35,66,95,97] in some, but not all, geographic areas [35,101,102]. Black-tailed prairie dogs enhance the diversity of vegetation, vertebrates, and invertebrates through their foraging and burrowing activities and by their presence as prey items [21,35,103,141,144]. Grasslands inhabited by black-tailed prairie dogs support higher biodiversity than grasslands not occupied by black-tailed prairie dogs [32,95]. See Ceballos and others [21] for a simplified diagram of black-tailed prairie dog activities and impacts in grassland ecosystem function and biological diversity.
Hundreds of species of vertebrates [99,120] and invertebrates [82,124,144] are associated with black-tailed prairie dog colonies. Vertebrate species richness on black-tailed prairie dog colonies increases with colony size and density [111]. West of the Missouri River in Montana, 40% (100 species) of all vertebrate fauna in prairie habitats rely on black-tailed prairie dog colonies for food, nesting, and/or denning [48]. Rare and declining species such as the black-footed ferret [24,43,47,55,63,99,120,128], swift fox (Vulpes velox), mountain plover (Charadrius montanus) [111], and burrowing owl (Athene cunicularia) [15,69,91,93,104,106,107,131,132] are associated with black-tailed prairie dog colonies [95,99]. Because black-tailed prairie dog foraging activities keep plant development in a suppressed vegetative state with higher nutritional qualities [89,120], herbivores including elk (Cervus elaphus), American bison (Bos bison), pronghorn (Antilocarpa americana), and domestic cattle often prefer foraging in black-tailed prairie dog colonies [12,29,30,59,69,75,79,81,103,120]. Animals that depend on herbaceous cover in sagebrush habitat, such as mule deer (Odocoileus hemionus) and sage grouse (Centrocercus spp.), may be deterred by the decreased vegetative cover on black-tailed prairie dog colonies [71]. For a list of vertebrate species associated with black-tailed prairie dog colonies, see Campbell and Clark [16].
Biodiversity in shortgrass prairies may be at risk due to the reductions in distribution and occurrence of black-tailed prairie dog [82]. Threats to black-tailed prairie dogs include fragmentation and loss of habitat, unregulated eradication or control efforts, and sylvatic plague [90,99]. As a result of habitat fragmentation and prairie dog eradication programs, black-tailed prairie dog colonies are now smaller and more fragmented than in presettlement times. Agriculture, livestock use, and other development have reduced black-tailed prairie dog habitat to 2% of its former range [99]. Fragmented black-tailed prairie dog colonies are more susceptible to extirpation, primarily by sylvatic plague [95]. The effect of roads on black-tailed prairie dogs is debatable. Roads may either facilitate or hinder black-tailed prairie dog movement, depending on the landscape setting. Roads may be easy routes for dispersal, but those with heavy automobile use may increase black-tailed prairie dog mortality [26,79]. Roads, streams, and lakes may serve as barriers to sylvatic plague in black-tailed prairie dog colonies [26].
According to Reading and Beissinger [111] and Lomolino and Smith [88], a primary management goal of black-tailed prairie dog ecosystems should be the maintenance of biodiversity. Maintaining a network of native prairie reserves located in large clusters as well as large, isolated colonies across the black-tailed prairie dog's historic range is recommended [88,111]. Mulhern and Knowles [99] recommend that 1% to 3% of suitable grasslands should be occupied by black-tailed prairie dogs, and 5% to 10% of federally-owned lands should be occupied by black-tailed prairie dogs. In 1990, Miller and others [96] suggested an integrated management plan that satisfies cattle ranching needs and the conservation of grasslands. They proposed that federal money allocated to the black-tailed prairie dog poisoning program be converted into a rebate for ranchers that manage livestock and preserve black-tailed prairie dog colonies [96]. In 1970, Linder and others [87] recommended preserving black-tailed prairie dog colonies for black-footed ferrets by obtaining easements. Ranchers could continue grazing cattle in a normal manner, but an easement would stipulate that black-tailed prairie dogs could not be eliminated or controlled using methods that are detrimental to ferrets. The rancher could be compensated for an increase in the size of black-tailed prairie dog colonies [87].
A habitat suitability index model for black-tailed prairie dog was created by Clippinger [25] to produce indices for year-round habitat requirements for the black-tailed prairie dog. Possible uses of the model include the evaluation of current colony sites for habitat suitability, the evaluation of possibilities for black-tailed prairie dog colony expansion, and the suitability of sites of transplantation or rehabilitation of black-tailed prairie dog. Four habitat variables are considered: percent herbaceous cover, percent slope, height of vegetation, and soil composition. According to the model, any area of short-grass or mixed-grass prairie >6.2 acres (0.25 ha) is suitable habitat for black-tailed prairie dog. Optimal features include silty clay loam soil, ≥15% herbaceous cover with vegetation 3 to 5 inches (7-13 cm) tall, and ≤10% slope [25].
Interactions with domestic livestock: While black-tailed prairie dogs are often regarded as competitors with livestock for available forage, evidence of impacts on rangelands are mixed. Some research suggests that black-tailed prairie dogs have either neutral or beneficial effects on rangeland used by livestock [12,59,81,103]; however, effects of black-tailed prairie dogs on rangelands are not uniform [29,30,71]. In Cimarron National Grassland in southwest Kansas and adjacent private lands in Baca County, Colorado, some vegetational differences were detected between areas colonized by black-tailed prairie dogs and non-colonized areas, although not all differences were consistent among sample years. Species richness and diversity indices did not differ (P>0.05) among colonized and non-colonized sites in either year, nor did the amount of bare ground (P>0.05). The authors conclude that while prairie dogs alter shortgrass prairie such that the vegetation of colonies tends to be distinct from adjacent non-colonized areas, Âprairie dogs do not substantially alter the essential character of shortgrass vegetation [146]. Cattle neither significantly preferred nor avoided black-tailed prairie dog colonies in a study in the shortgrass steppe of northeastern Colorado. Cattle used black-tailed prairie dog colonies in proportion to the colony's availability, and grazed as intensively on colonies as on areas not occupied by black-tailed prairie dog [53].
Competitive interactions between black-tailed prairie dogs and domestic livestock for preferred forage species are unclear. Several studies suggest that black-tailed prairie dogs avoid eating many plants that livestock prefer, and prefer many plants that livestock avoid [29,30,103,136]. Conversely, on shortgrass prairie in Colorado, cattle and black-tailed prairie dogs had a 64% similarity in annual diet [59].
Some changes in plant composition brought about by black-tailed prairie dogs may benefit livestock by encouraging an increase in plants that are more tolerant of grazing, such as needleleaf sedge (Carex duriuscula), sixweeks grass (Vulpia octoflora), and scarlet globemallow [12,89,120]. Grazing by black-tailed prairie dogs may also improve the nutritional qualities of some plants [89,120]. On a shortgrass prairie near Fort Collins, Colorado, plant species diversity was greater inside black-tailed prairie dog colonies than outside of colonies, and perennial grasses such as buffalo grass and forbs increased [12]. While black-tailed prairie dog colonies at Wind Cave National Park typically had lower levels of plant biomass and were dominated by forbs, plants growing on prairie dog colonies had higher leaf nitrogen concentrations than plants in mixed-grass prairie outside colonies [39]. Foraging by black-tailed prairie dogs does not significantly (P>0.05) affect steer weights [59,103]. While forage availability and utilization by cattle decreased in black-tailed prairie dog foraging areas, there was no significant (P>0.05) reduction of steer weight in either of 2 years of study at the USDA's Southern Great Plains Experimental Range near Woodward, Oklahoma. Nutrient cycling, increased soil fertility, and subsequent changes in forage quality partly compensated for reduced forage availability [103].
Relocation: Black-tailed prairie dogs may need to be relocated for re-establishment into areas where they were extirpated, or to ensure no net loss of prairie dog habitat due to development or agriculture. Factors to consider when relocating black-tailed prairie dogs include: soil, slope, elevation, vegetation type, previous use of a site by black-tailed prairie dog, proximity to other black-tailed prairie dog colonies and adjacent landowners, and natural dispersal barriers. See Roe and Roe [116] for details. After relocation, black-tailed prairie dogs may be retained by 1) ensuring that relocation habitat is suitable, 2) use of underground nest chambers modeled after natural nest chambers, 3) acclimating black-tailed prairie dogs to release sites in large retention pens, and 4) providing supplemental food and water as necessary [117]. Survival of captive prairie dogs upon release into the wild may be enhanced by predator training at a young age [123]. In a study conducted by Shier and Owings [123], predators were presented to captive juvenile black-tailed prairie dogs in conjunction with playbacks of black-tailed prairie dog alarm vocalizations. These techniques had an immediate and lasting effect on black-tailed prairie dogs and enhanced predator avoidance once they were released [123].
Control: It is easier to discourage black-tailed prairie dogs before they inhabit an area than to try to eliminate them after they have established a colony [81]. A minimum of 77% elimination of black-tailed prairie dogs must be achieved the first year. If the remaining 23% of the population is not removed, a complete repopulation may occur within 3 years [31]. A cost-benefit analysis revealed that black-tailed prairie dog poisoning costs more than any grazing benefits accrued [95,96]. Additionally, animals such as American badgers, foxes (Vulpes spp.), coyotes, bobcats, weasels (Mustela spp.), golden eagles, and hawks (Buteo spp.) are potential indirect targets of poisoning programs [81]. Shooting black-tailed prairie dogs for population control and recreation is common across their range [69,90,99]. Shooting may decrease the health of black-tailed prairie dog colonies, fragment populations, cause the loss of non-target species, and delay recovery of colonies affected by sylvatic plague [90].
Visual barriers may be an effective, non-lethal method of black-tailed prairie dog control in mixed-grass prairies. By placing a visual obstruction at 1 side of a colony, expansion of the colony in that direction is limited due to the obstruction of the panoramic view. Physical barriers such as steep slopes and tall vegetation with grass stems about 1.5 inches (3.8 cm) apart and >1 foot (12 inches) tall are an effective barrier against black-tailed prairie dog colony expansion [81]. Koford [81] suggests changing a cattle grazing practice to alter the range vegetation and minimize the quick reoccurrence of black-tailed prairie dog damage. To establish a different plant community unsuitable to black-tailed prairie dogs, complete rest for the range or reseeding is suggested. Specialized predators of black-tailed prairie dogs could also be encouraged. For example, poles may be installed in black-tailed prairie dog colonies to encourage predatory raptors to inhabit the area [81].
Habitat preferences for the black-tailed prairie dog are influenced by vegetative cover type, slope, soil type, and amount of rainfall [111]. Black-tailed prairie dog foraging and burrowing activities influence environmental heterogeneity, hydrology, nutrient cycling, biodiversity, landscape architecture, and plant succession in grassland habitat [12,22,29,30,48,50,75,81,139,141,146].
Landscape-scale habitat characteristics: Black-tailed prairie dogs inhabit grasslands including short- and mixed-grass prairie, sagebrush steppe, and desert grasslands (see Plant Communities). Shortgrass prairies dominated by buffalo grass (Buchloe dactyloides), blue grama (Bouteloua gracilis), and western wheatgrass (Pascopyron smithii) [25,37,59,75,81], and mixed-grass prairies [12,23,25,28,36,45,50,71,99] that have been grazed by native and nonnative herbivores are preferred habitat [79,81]. Slopes of 2% to 5% and vegetation heights between 3 and 5 inches (7-13 cm) are optimal for detecting predators and facilitating communication [25,27,37,75,81].
In the Great Plains region, black-tailed prairie dog colonies commonly occur near rivers and creeks [81]. Of 86 black-tailed prairie dog colonies located in Mellette County, South Dakota, 30 were located on benches or terraces adjacent to a creek or floodplain, 30 occurred in rolling hills with a slope >5%, 20 were in flat areas, and 6 were in badland areas [64]. The slopes of playa lakes in the Texas panhandle and surrounding regions are used as habitat for the black-tailed prairie dog [108,109,110]. Black-tailed prairie dog colonies in Phillips County, Montana, were often associated with reservoirs, cattle salting grounds, and other areas affected by humans [111].
Black-tailed prairie dogs tolerate "high degrees" of disturbance over long periods of time [27,52]. New colonies are rarely created on rangeland that is in "good" to "excellent" condition; however, land that is continually heavily grazed for decades reduces habitat quality due to soil erosion [115]. Black-tailed prairie dogs may colonize heavily grazed sites but do not necessarily specialize in colonizing overgrazed areas. Overgrazing may occur subsequent to black-tailed prairie dog colonization [127]. Black-tailed prairie dogs were associated with areas intensively grazed by livestock and/or areas where topsoil had been disturbed by human activities in sagebrush-grassland habitat on the Charles M. Russell National Wildlife Refuge and Fort Belknap Indian Reservation in northeastern Montana. Roads and cattle trails were found in 150 of 154 black-tailed prairie dog colonies, and colonies were located significantly (P<0.001) closer to livestock water developments and homestead sites than randomly located points [79].
Site-scale habitat characteristics:
Vegetation: Plant community structure and species composition are impacted by black-tailed prairie dog colonization, and are related to the age of the colony and the level of expansion taking place [29,30,128]. Vegetation on black-tailed prairie dog colonies is typically of lower stature [50,75,81,146], and characterized by a higher percentage of bare ground, a higher cover of forbs and/or dwarf shrubs, and lower cover of grasses and larger woody plants than surrounding grassland [7,81,139]. As the black-tailed prairie dog colony ages, forbs and dwarf shrubs may dominate; younger colonies are dominated by grasses [29,141]. Black-tailed prairie dog colonies in Wind Cave National Park consisted of 3 vegetational zones. The interior zone was dominated by forbs, the edge zone was dominated by shortgrasses such as blue grama and buffalo grass, and the outer zone consisted of undisturbed mixed-grass prairie dominated by western wheatgrass, grama (Bouteloua spp.), and needlegrass (Stipa spp.) [50].
Shifts in vegetational structure and composition seem to occur about 10 or more years following initial colonization [23,29]. In a mixed-grass prairie in Badlands National Park, South Dakota, a buffalo grass-dominated community remained relatively unchanged 4 to 7 years after a colony was established. When cover of shortgrass (primarily buffalo grass) fell below 75%, about 11 to 13 years after colonization, abrupt vegetational changes occurred. Forbs, armed and/or sprawling grasses, aromatic dicots, and bare ground dominated the area [23]. In Wind Cave National Park, changes in relative cover of graminoids, forbs, and dwarf shrubs occurred sometime between 8 and 26 years following black-tailed prairie dog colonization, while a decrease in litter and an increase in bare ground were detectable 1 to 2 years after colonization, as shown in following table [29]:
Ground cover (%) composition before (0 years) and during 26 years of black-tailed prairie dog colonization [29]
Age (years)
0
1 to 2
3 to 8
>26
graminoids 26 26 25 1 forbs and dwarf shrubs 10 7 11 29 total vegetation 36 33 36 30 litter 48 37 39 11 bare ground 16 30 25 59According to Cid and others [22], the rate of vegetation change after the removal of grazing animals such as black-tailed prairie dogs is influenced by many factors, including grassland type, plant species composition, weather conditions, and prior intensity and duration of grazing [22]. Removal of black-tailed prairie dogs from a landscape by natural or anthropogenic factors could either release suppressed populations of woody plants or provide new habitat for woody plant colonization [4]. The removal of prairie dogs from northern mixed-grass prairies in Badlands National Park, South Dakota, did not result in rapid reestablishment of native vegetation. When seed banks were collected from black-tailed prairie dog colonies, few dominant species typical of mixed-grass prairie germinated in the laboratory compared to seed banks collected off of black-tailed prairie dog colonies. The authors suggested that unless the seed bank is restored, rapid reestablishment of representative mixed-grass prairie would be difficult [45]. In northeastern Colorado, vegetation changes following eradication of black-tailed prairie dogs were relatively minor and did not significantly (P-value not given) improve shortgrass prairie for use by cattle within 5 years. The following table shows vegetation composition on 1 active and 3 abandoned black-tailed prairie dog colonies in a shortgrass prairie. Plant species in the table were listed only if they had >0.5% cover [77]:
Vegetation cover (%) on active and inactive black-tailed prairie dog colonies [77]
Vegetation Active colony 1 year abandoned 2 years abandoned 5 years abandoned western wheatgrass 2.3 5.1 6.9 6.7 ring muhly (Muhlenbergia torreyi) 5.5 0.2 9.0 0.7 Indian ricegrass (Achnatherum hymenoides) ---- ---- ---- 0.6 purple threeawn 2.8 0.4 0.2 0.3 blue grama 20.7 22.8 9.8 22.2 buffalo grass 37.2 32.4 31.9 25.0 perennial grasses (subtotal) 68.5 60.8 57.7 55.2 annual grasses (2 species) ---- 0.1 ---- 0.5 forbs (14 species) 0.1 2.2 0.6 0.4 shrubs/half-shrubs (6 species) 2.1 2.7 1.9 2.0Total vegetation cover (27 species)
70.7 65.5 60.3 58.3Other habitat characteristics: Black-tailed prairie dog distribution is not limited by soil type, but by indirect effects of soil texture on moisture and vegetation. Black-tailed prairie dog colonies occur in many types of soil including deep, alluvial soils with medium to fine textures, and occasionally gravel. Soil that is not prone to collapsing or flooding is preferred [81]. Black-tailed prairie dogs do not select specific types of soil to dig burrows [75], but silty loam clay soils are best for tunnel construction [81]. Surface soil textures in black-tailed prairie dog colonies near Fort Collins, Colorado, varied from sandy loam to sandy clay loam in the top 6 inches (15 cm), with a sandy clay loam subsoil [11]. In northern latitudes, black-tailed prairie dog colonies commonly occur on south aspects due to the dominance of grasses over shrubs and increased solar radiation during winter. Burrows usually occur on slopes <10% [81].
Black-tailed prairie dogs mix the soil horizons by raising soil from deeper layers to the surface. This may significantly affect the texture and composition of soil at different layers. Feces, urine, and carcasses of black-tailed prairie dogs also affect soil characteristics [81].
Home range and population density: The home range and territorial boundaries of black-tailed prairie dogs are determined by the area occupied by an individual coterie. Coteries typically occupy about 1.0 acre (0.4 ha) [81].
Population density and growth are influenced by habitat quality [75,111] and are restricted by topographic barriers, soil structure, tall vegetation, and social conditions [75,81]. Urbanization and other types of human development may restrict colony size and spatial distribution [70]. Most plains habitats support at least 13 black-tailed prairie dogs/ha [81]. In a mixed-grass prairie at Wind Cave National Park, black-tailed prairie dog population densities were as follows [75]:
Black-tailed prairie dog density from 1948 to 1950 [75] Sample date Area of black-tailed prairie dog ward (acres (ha)) PopulationAverage
5.6 (2.3) 50 8.8The currently accepted scientific name for the black-tailed prairie dog is Cynomys ludovicianus
(Ord) [6,54,56,145].
Although not typically distinguished, 2 subspecies were described by Hall
[54]:
Cynomys ludovicianus arizonensis Mearns
Cynomys ludovicianus ludovicianus (Ord) [54]
Age of first reproduction, pregnancy rate, litter size, juvenile growth rate, and first-year survivorship of the black-tailed prairie dog vary depending on food availability [50].
Mating: Minimum breeding age for the black-tailed prairie dog is usually 2 years [69,75,81], but yearlings may breed if space and food are abundant [75,81]. In Wind Cave National Park, South Dakota, 40% (n=213) of yearling females copulated and 9% successfully weaned a litter [66].
The mating season occurs from late February through April, but varies with latitude and site location of a black-tailed prairie dog colony [75,81]. Estrus occurs for only 1 day during the breeding season [66].
Reproductive success: In Wind Cave National Park, the mean percentage of adult females that weaned a litter each year was 47% ± 14% SD (range 30% to 73% over 10 years) [67]. Reproductive success and survival may be greater in young black-tailed prairie dog colonies that have space for expansion. In a young colony (@5 years) with space for expansion in Wind Cave National Park, 88% females were pregnant and 81% of young weaned, compared to an old colony (@30 years) with no room for expansion, where 90% of females were pregnant and 41% of young were weaned [50].
Gestation period and litter size: Black-tailed prairie dog gestation is 34 days [69,75]. Parturition occurs underground. Information about litter size at time of birth is unavailable [65]. Mean litter size observed aboveground ranges from 3.0 to 4.9 young/litter [66,67,75,81]. Only 1 litter is produced each year [66,67].
Development: In captivity, black-tailed prairie dog pups open their eyes at 30 days old [75]. Pups are altricial and remain below ground for @7 weeks to nurse [66,75,81]. Maturity is complete at 15 months old [75]. Lifespan of the black-tailed prairie dog in the wild is unknown, but males >3 years old experience high mortality. Females may live longer than males [75]. According to Hoogland and others [67], lifespan is about 5 years for males and 7 years for females.
Social organization: Black-tailed prairie dogs live in colonies. Colony size may range from 5 to thousands of individuals. Colonies are subdivided into 2 or more wards, based on topographic features, such as hills. Wards are usually subdivided into 2 or more coteries, which are composed of aggregates of highly territorial, harem-polygynous social groups [75,81]. Individuals within coteries are amicable with each other and hostile towards non-coterie individuals [49,75]. At the beginning of the breeding season, a coterie is typically composed of 1 adult male, 3 to 4 adult females, and several yearlings and juveniles of both sexes [31,75]. After the breeding season and prior to dispersal of juveniles, coterie size increases [31,75].
Habits: Black-tailed prairie dogs are diurnal [69,75,81]. Aboveground activity is reduced when rain or snow is falling and during days when the temperature exceeds 100 °F (38° C) [75,81]. They do not hibernate [61] but may become dormant for short periods [66,75,81].
Dispersal: Reasons for dispersal include new vegetative growth at colony peripheries, shortage of unrelated females in a coterie, harassment of females by juveniles, and probably an innate genetic mechanism responding to increased density within a colony [49]. Males typically leave the natal territory 12 to 14 months after weaning, during May and June [67], but dispersal may occur throughout the year [49]. Females generally remain in their natal coterie territories for their lifetime. Intercolony dispersers moved an average distance of 1.5 miles (2.4 km) from their natal site [67]. Roads and trails may facilitate black-tailed prairie dog dispersal [81].
Mortality: Major mortality factors include predation (see Predators), disease, infanticide, habitat loss, poisoning, trapping, and shooting [26,66,67,69,69]. Survivorship for the first year was 54% for females and <50% for males in Wind Cave National Park. Primary causes of death were predation and infanticide [66]. Infanticide partially or totally eliminated 39% (n=361) of all litters. Lactating females were the most common killers [66]. Mortality of young was highest due to heavy predation during the winter and early spring following birth [75]. Mortality increases with dispersal from a colony or coterie [81].
Sylvatic plague, caused by the bacterium Yersinia pestis, can quickly eliminate entire black-tailed prairie dog colonies. Once infected, death occurs within a few days [26,69]. Black-tailed prairie dogs are also susceptible to diseases transmitted by "introduced animals" (species not identified) [13,14].
Human-caused mortality of black-tailed prairie dogs is discussed in Management considerations.
Fire may have negative or positive effects on black-tailed prairie dog habitat depending on burn severity and season. Low-severity burns conducted during spring in non-drought years may stimulate the growth of black-tailed prairie dog colonies by reducing vegetational height and density at the colony periphery [40,42,62,68,72,76,78,98,100,113,133,142]. High-severity burns have the potential of altering the plant community in a black-tailed prairie dog colony, reducing its quality of habitat, at least in the short-term [128]. During the plant growing season, the absence of fire provides optimal conditions for black-tailed prairie dog colony growth [78].
Prescribed burning and mechanical brush removal around the perimeter of black-tailed prairie dog colonies may encourage their expansion. Fire exclusion may be an effective, nonlethal management tool for reducing the expansion of black-tailed prairie dog colonies [98].
The black-tailed prairie dog (Cynomys ludovicianus) is a rodent of the family Sciuridae found in the Great Plains of North America from about the United States-Canada border to the United States-Mexico border. Unlike some other prairie dogs, these animals do not truly hibernate. The black-tailed prairie dog can be seen above ground in midwinter. A black-tailed prairie dog town in Texas was reported to cover 25,000 sq mi (64,000 km2) and included 400,000,000 individuals.[3] Prior to habitat destruction, the species may have been the most abundant prairie dog in central North America. It was one of two prairie dogs described by the Lewis and Clark Expedition in the journals and diaries of their expedition.
Black-tailed prairie dogs are generally tan in color, with lighter-colored bellies. They may have color variation in their pelt, such as dark fur on their back in black and brown tones. Their tails have black tips, from which their name is derived. Adults can weigh from 1.5 to 3.0 lb (0.68 to 1.36 kg), males are typically heavier than females. Body length is normally from 14 to 17 in (36 to 43 cm), with a 3-to-4 in (7.6-to-10.2 cm) tail. The black-tailed have black long claws used for digging. The body of the black-tailed prairie dog is compact, and the ears are small and close to the head.
The historic range of the black-tailed prairie dog was from southern Saskatchewan and Alberta to Chihuahua, Mexico,[4] and included portions of Montana, North Dakota, South Dakota, Wyoming, Colorado, Nebraska, Kansas, Oklahoma, Texas, Arizona, and New Mexico.[5] As of 2007, black-tailed prairie dogs occur across most of their historic range, excluding Arizona;[6][7] however, their occupied acreage and populations are well below historic levels.[8]
Black-tailed prairie dogs are diurnal.[6][9][10] Above-ground activity is reduced when rain or snow is falling and during days when the temperature exceeds 100 °F (38 °C).[9][10] During the winter months, black-tailed prairie dogs do not fully hibernate. They continue to leave the burrow to forage, but will enter a state of torpor at night to conserve energy. Torpor is categorized by a drop in metabolism, heart rate and respiration similar to hibernation, but is involuntary and shorter in duration. On average, black-tailed prairie dogs will lose twenty percent of their body weight during the fall and winter seasons when they go through bouts of torpor. As winter progressed, the amount of time spent in torpor increases. Between different colonies the overall time spent in torpor varies, independent of prairie dog body mass. This may be due to weather during the previous growing season. As black-tailed prairie dogs receive most of their water from their diet, in years with poor rainfall, the black-tailed prairie dogs spend more time in torpor.[11]
Black-tailed prairie dogs are native to grassland habitats in North America. They inhabit shortgrass prairie,[7][12][13] mixed-grass prairie,[7][14][15][16][17][18] sagebrush steppe,[12][19] and desert grassland.[4][20]
Habitat preferences for the black-tailed prairie dog are influenced by vegetative cover type, slope, soil type, and amount of rainfall.[21] Their foraging and burrowing activities influence environmental heterogeneity, hydrology, nutrient cycling, biodiversity, landscape architecture, and plant succession in grassland habitats.[9][10][15][17][22][23]
Black-tailed prairie dogs inhabit grasslands, including short- and mixed-grass prairie, sagebrush steppe, and desert grasslands. Shortgrass prairies dominated by buffalo grass (Buchloe dactyloides), blue grama (Bouteloua gracilis), and western wheatgrass (Pascopyron smithii),[9][10][14][24] and mixed-grass prairies [7][14][15][16][17][18] that have been grazed by native and non-native herbivores are their preferred habitat.[10][19] Slopes of 2% to 5% and vegetation heights between 3 and 5 in (7–13 cm) are optimal for detecting predators and facilitating communication.[9][10][14]
In the Great Plains region, black-tailed prairie dog colonies commonly occur near rivers and creeks.[10] Of 86 colonies located in Mellette County, South Dakota, 30 were located on benches or terraces adjacent to a creek or floodplain, 30 occurred in rolling hills with a slope more than 5°, 20 were in flat areas, and six were in badland areas.[25] The slopes of playa lakes in the Texas Panhandle and surrounding regions are used as habitat for the black-tailed prairie dog.[26] Colonies in Phillips County, Montana, were often associated with reservoirs, cattle salting grounds, and other areas affected by humans.[21]
Black-tailed prairie dogs tolerate "high degrees" of disturbance over long periods of time. New colonies are rarely created on rangeland in "good" to "excellent" condition; however, continuously, long-term, heavily grazed land reduces habitat quality due to soil erosion.[27] Black-tailed prairie dogs may colonize heavily grazed sites, but do not necessarily specialize in colonizing overgrazed areas. Overgrazing may occur subsequent to their colonization.[28] Black-tailed prairie dogs were associated with areas intensively grazed by livestock and/or areas where topsoil had been disturbed by human activities in sagebrush-grassland habitat on the Charles M. Russell National Wildlife Refuge and Fort Belknap Agency, Montana. Roads and cattle trails were found in 150 of 154 black-tailed prairie dog colonies, and colonies were located significantly closer to livestock water developments and homestead sites than randomly located points.[19]
Black-tailed prairie dog distribution is not limited by soil type, but by indirect effects of soil texture on moisture and vegetation. Colonies occur in many types of soil, including deep, alluvial soils with medium to fine textures, and occasionally gravel. Soil not prone to collapsing or flooding is preferred.[10] Though they do not select specific types of soil to dig burrows,[9] silty loam clay soils are best for tunnel construction.[10] Surface soil textures in colonies near Fort Collins, Colorado, varied from sandy loam to sandy clay loam in the top 6 in (15 cm), with a sandy clay loam subsoil. In northern latitudes, colonies commonly occur on south aspects due to the dominance of grasses over shrubs and increased solar radiation during winter. Burrows usually occur on slopes more than 10°.[10]
Black-tailed prairie dogs mix the soil horizons by raising soil from deeper layers to the surface. This may significantly affect the texture and composition of soil at different layers. Their feces, urine, and carcasses also affect soil characteristics.[10]
The home range and territorial boundaries of black-tailed prairie dogs are determined by the area occupied by an individual coterie. Coteries typically occupy about 1.0 acre (0.4 ha).[10]
Population density and growth are influenced by habitat quality [9] and are restricted by topographic barriers, soil structure, tall vegetation, and social conditions.[9][10] Urbanization and other types of human development may restrict colony size and spatial distribution. Most plains habitats support at least 13 black-tailed prairie dogs/ha.[10]
Burrows created by black-tailed prairie dogs serve as refuges from the external environment and are one of the most important features of their colonies. Burrows are used for breeding, rearing young, and hiding from predators, and are maintained from generation to generation, and serve as stabilizers on the physical and social aspects of the colony.[9] Black-tailed prairie dog nests are located underground in burrows and are composed of fine, dried grass. Nest material is collected throughout the year by both sexes and all age classes.[6][9] Tunnel depths in central Oklahoma were typically 50–60 in deep.[29] Most colonies contain 20 to 57 burrows/acre.[9][10]
The three types of burrow entrances are: dome mounds, rimmed crater mounds, and entrances without structures around them. Entrance features may prevent flooding and/or aid in ventilation.[6][9][10] Dome mounds consist of loosely packed subterranean soil spread widely around the entrance of the burrow, and tend to be vegetated by prostrate forbs. Rimmed crater mounds are cone-shaped and constructed of humus, litter, uprooted vegetation, and mineral soil. Black-tailed prairie dogs compact the soil of these mounds with their noses, creating poor sites for seedling establishment.[16] Rimmed crater mounds may be used as wallowing sites for American bison. Burrow entrances without structures around them are usually located on slopes more than 10°.[9] The density of burrow openings depends on both substrate and duration of occupation of an area.[10]
Vegetation heights between 3 and 5 in (7–13 cm) and a slope of 2° to 5° are optimal for detecting predators and facilitating communication among black-tailed prairie dogs.[9][10][14] Grazing cattle keep vegetation short in the vicinity of colonies, reducing susceptibility to predators and potentially expanding colony size.[9][10][20][24] Black-tailed prairie dogs were rarely seen feeding more than 16 ft (5 m) from colony edges in Wind Cave National Park.[17]
Black-tailed prairie dogs are selective opportunists, preferring certain phenological stages or types of vegetation according to their needs.[9][14][30] When forage is stressed by grazing, drought, or herbicides, they change their diets quickly. Grasses are preferred over forbs,[10][24] and may comprise more than 75% of their diets, especially during summer.[24][30] Western wheatgrass, buffalo grass, blue grama [9][10][30] and sedges (Carex spp.) are preferred during spring and summer. Scarlet globemallow (Sphaeralcea coccinea) [9][15][24][30] and Russian thistle (Salsola kali) [31] are preferred during late summer and fall, but are sought out during every season.[10][15][24] During winter, plains prickly pear (Opuntia polyacantha), Russian thistle, and underground roots are preferred.[9][30] Shrubs such as rabbitbrush (Chrysothamnus spp.), winterfat (Krascheninnikovia lanata), saltbush (Atriplex spp.), and sagebrush (Artemisia spp.) are also commonly eaten.[31] Water, which is generally not available on the short-grass prairie, is obtained from vegetation such as plains prickly pear.[30] Koford [10] estimated one black-tailed prairie dog eats about 7 lb (3 kg) of herbage per month during summer.[31] Cutworms,[31] grasshoppers,[10] and old or fresh American bison scat are occasionally eaten.[6] For a detailed list of foods eaten by black-tailed prairie dogs by month, and ratings of those foods' forage value to cattle and sheep, see.[31] For a complete list of vegetation preferred by the black-tailed prairie dog, see.[32]
Black-tailed prairie dogs live in colonies. Colony size may range from five to thousands of individuals, and may be subdivided into two or more wards, based on topographic features, such as hills. Wards are usually subdivided into two or more coteries, which are composed of aggregates of highly territorial, harem-polygynous social groups.[9][10] Individuals within coteries are amicable with each other and hostile towards outside individuals. At the beginning of the breeding season, a coterie is typically composed of one adult male, three to four adult females, and several yearlings and juveniles of both sexes. After the breeding season and prior to dispersal of juveniles, coterie size increases.[9]
Reasons for dispersal include new vegetative growth at colony peripheries, shortage of unrelated females in a coterie, harassment of females by juveniles, and probably an innate genetic mechanism responding to increased density within a colony. Males typically leave the natal territory 12 to 14 months after weaning, during May and June,[33] but dispersal may occur throughout the year. Females generally remain in their natal coterie territories for their lifetimes. Intercolony dispersers moved an average distance of 1.5 mi (2.4 km) from their natal site.[33] Roads and trails may facilitate black-tailed prairie dog dispersal.[10]
Black-tailed prairie dogs have sensory adaptions for avoiding predators. Black-tailed prairie dogs have very sensitive hearing at low frequencies that allows them to detect predators early, especially while in their burrows. Black-tailed prairie dog hearing can range from 29 Hz to 26 kHz, and can hear as low as 4 Hz.[34]
Constantine Slobodchikoff and others assert that prairie dogs use a sophisticated system of vocal communication to describe specific predators.[35] According to them, prairie dog calls contain specific information as to what the predator is, how big it is, and how fast it is approaching.[35] These have been described as a form of grammar. According to Slobodchikoff, these calls, with their individuality in response to a specific predator, imply prairie dogs have highly developed cognitive abilities.[35] He also asserts prairie dogs have calls for things that are not predators to them. This is cited as evidence that the animals have a very descriptive language and have calls for any potential threat.[35]
Debate exists over whether the alarm calling of prairie dogs is selfish or altruistic. Prairie dogs possibly alarm others to the presence of a predator so they can protect themselves. However, the calls possibly are meant to cause confusion and panic in the groups and cause the others to be more conspicuous to the predator than the caller. Studies of black-tailed prairie dogs suggest alarm calling is a form of kin selection, as a prairie dog's call alerts both offspring and kin of indirect descent, such as cousins, nephews, and nieces.[36] Prairie dogs with kin close by called more often than those without. In addition, the caller may be trying to make itself more noticeable to the predator.[36] However, a predator seems to have difficulty determining which prairie dog is making the call due to its "ventriloquistic" nature.[36] Also, when a prairie dog makes a call, the others seem not to run into the burrows, but stand on the mounds to see where the predator is, making themselves visible to the predator.[36]
Perhaps the most conspicuous prairie dog communication is the territorial call or "jump-yip" display. A prairie dog will stretch the length of its body vertically and throw its forefeet into the air while making a call.[37] A jump-yip from one prairie dog causes others nearby to do the same.[38] The instigator of the jump-yip 'wave' uses the jump-yip to assess the vigilance or watchfulness of others in the colony - a longer jump-yip wave indicates watchful neighbors and leads to increased foraging by the instigator.[39]
Age of first reproduction, pregnancy rate, litter size, juvenile growth rate, and first-year survival of the black-tailed prairie dog vary depending on food availability.[17]
Minimum breeding age for the black-tailed prairie dog is usually two years,[6][9][10] but yearlings may breed if space and food are abundant.[9][10] In Wind Cave National Park, South Dakota, 40% (213 individuals) of yearling females copulated and 9% successfully weaned a litter.[40]
The mating season occurs from late February through April, but varies with latitude and site location of the colony.[9][10] Estrus occurs for only one day during the breeding season.[40]
In Wind Cave National Park, the mean percentage of adult females that weaned a litter each year was 47% ± 14%.[33] Reproductive success and survival may be greater in young colonies that have space for expansion. In a young colony (five years) with space for expansion, in Wind Cave National Park, 88% females were pregnant and 81% of young weaned, compared to an old colony (30 years) with no room for expansion, where 90% of females were pregnant and 41% of young were weaned.[17]
Black-tailed prairie dog gestation is 34 days.[6][9] Parturition occurs underground. Information about litter size at time of birth is unavailable, but the mean litter size observed above ground ranges from 3.0 to 4.9 young/litter.[9][10][40][33] Only one litter is produced each year.[40][33]
In captivity, black-tailed prairie dog pups open their eyes at 30 days old.[9] Pups are altricial and remain below ground for up to seven weeks to nurse.[9][10][40] Maturity is complete at 15 months old.[9] Lifespan of the black-tailed prairie dog in the wild is unknown, but males more than 3 years old experience high mortality. Females may live longer than males.[9] According to Hoogland and others,[33] lifespan is about 5 years for males and 7 years for females.
Major mortality factors include predation, disease, infanticide, habitat loss, poisoning, trapping, and shooting.[6][40][12][33] Survival for the first year was 54% for females and less than 50% for males in Wind Cave National Park. Primary causes of death were predation and infanticide.[40] Infanticide partially or totally eliminated 39% (361 individuals) of all litters. Lactating females were the most common killers.[40] Mortality of young was highest due to heavy predation during the winter and early spring following birth.[9] Mortality increases with dispersal from a colony or coterie.[10]
Sylvatic plague, caused by the bacterium Yersinia pestis, can quickly eliminate entire black-tailed prairie dog colonies. Once infected, death occurs within a few days.[6][12] Black-tailed prairie dogs are also susceptible to diseases transmitted by introduced animals.[41]
The most common predators of black-tailed prairie dogs are coyotes (Canis latrans),[6][9][17][42] American badgers (Taxidea taxus),[6][10][17][42] bobcats (Lynx rufus),[6][9][42] golden eagles (Aquila chrysaetos),[6][9][10][42] ferruginous hawks (Buteo regalis),[6][42] red-tailed hawks (Buteo jamaicensis),[9] and prairie rattlesnakes (Crotalus viridis).[9][10][42] Although now very rare, black-footed ferrets (Mustela nigripes) were once a major predator of the black-tailed prairie dog.[42]
Black-tailed prairie dogs have been called "ecosystem engineers" due to their influence on the biotic and abiotic characteristics of their habitat, landscape architecture, and ecosystem structure and function.[4][43] Research suggests black-tailed prairie dogs are a keystone species[4][40][43] in some, but not all, geographic areas.[4] Black-tailed prairie dogs enhance the diversity of vegetation, vertebrates, and invertebrates through their foraging and burrowing activities and by their presence as prey items.[4][29][43][44] Grasslands inhabited by black-tailed prairie dogs support higher biodiversity than grasslands not occupied by them.
Hundreds of species of vertebrates [7][45] and invertebrates[29] are associated with black-tailed prairie dog colonies. Vertebrate species richness on their colonies increases with colony size and density.[21] West of the Missouri River in Montana, 40% (100 species) of all vertebrate fauna in prairie habitats rely on black-tailed prairie dog colonies for food, nesting, and/or denning. Rare and declining species, such as the black-footed ferret,[7][42][45] swift fox (Vulpes velox), mountain plover (Charadrius montanus),[21] and burrowing owl (Athene cunicularia)[6] are associated with colonies.[7] Because their foraging activities keep plant development in a suppressed vegetative state with higher nutritional qualities,[20][45] herbivores, including American bison, pronghorn (Antilocapra americana), and domestic cattle often prefer foraging in black-tailed prairie dog colonies.[6][9][10][15][19][22][24][44][45] Animals that depend on herbaceous cover in sagebrush habitat, such as mule deer (Odocoileus hemionus) and sage grouse (Centrocercus spp.), may be deterred by the decreased vegetative cover on black-tailed prairie dog colonies.[18] For a list of vertebrate species associated with black-tailed prairie dog colonies, see.[46]
Biodiversity in shortgrass prairies may be at risk due to the reductions in distribution and occurrence of black-tailed prairie dog. Threats include fragmentation and loss of habitat, unregulated eradication or control efforts, and sylvatic plague.[7][8] As a result of habitat fragmentation and prairie dog eradication programs, colonies are now smaller and more fragmented than in presettlement times. Agriculture, livestock use, and other development have reduced habitat to 2% of its former range.[7] Fragmented colonies are more susceptible to extirpation, primarily by sylvatic plague. The effect of roads on black-tailed prairie dogs is debatable. Roads may either facilitate or hinder their movement, depending on the landscape setting. Roads may be easy routes for dispersal, but those with heavy automobile use may increase mortality.[12][19] Roads, streams, and lakes may serve as barriers to sylvatic plague.[12]
Black-tailed prairie dogs are frequently exterminated from ranchland, being viewed as pests. Their habitat has been fragmented, and their numbers have been greatly reduced. Additionally, they are remarkably susceptible to plague.[47] In 2006, all eight appearances of plague in black-tailed prairie dog colonies resulted in total colony loss. Studies in 1961 estimated only 364,000 acres (1,470 km2) of occupied black-tailed prairie dog habitat in the United States. A second study in 2000 showed 676,000 acres (2,740 km2). However, a comprehensive study between 10 states and various tribes in 2004 estimated 1,842,000 acres (7,450 km2) in the United States, plus an additional 51,589 acres (208.77 km2) in Mexico and Canada. Based on the 2004 studies, the US Fish and Wildlife Service removed the black-tailed prairie dog from the Endangered Species Act Candidate Species List in August 2004.[48]
While black-tailed prairie dogs are often regarded as competitors with livestock for available forage, evidence of impacts on rangelands are mixed. Some research suggests they have either neutral or beneficial effects on rangeland used by livestock;[10][15][24][44] however, their effects on rangelands are not uniform.[18][22] In Cimarron National Grassland in southwest Kansas and adjacent private lands in Baca County, Colorado, some vegetational differences were detected between areas colonized by black-tailed prairie dogs and uncolonized areas, although not all differences were consistent between sample years. Species richness and diversity indices did not differ among colonized and uncolonized sites in either year, nor did the amount of bare ground. The authors conclude while prairie dogs alter shortgrass prairie such that the vegetation of colonies tends to be distinct from adjacent uncolonized areas, "prairie dogs do not substantially alter the essential character of shortgrass vegetation".[23] Cattle neither significantly preferred nor avoided black-tailed prairie dog colonies in a study in the shortgrass steppe of northeastern Colorado. Cattle used colonies in proportion to the colony's availability, and grazed as intensively on colonies as on areas not occupied by black-tailed prairie dogs.[13]
Competitive interactions between black-tailed prairie dogs and domestic livestock for preferred forage species are unclear. Several studies suggest black-tailed prairie dogs avoid eating many plants that livestock prefer, and prefer many plants livestock avoid.[22][44] Conversely, on shortgrass prairie in Colorado, cattle and black-tailed prairie dogs had a 64% similarity in annual diets.[24]
Some changes in plant composition brought about by black-tailed prairie dogs may benefit livestock by encouraging an increase in plants more tolerant of grazing, such as needleleaf sedge (Carex duriuscula), sixweeks grass (Vulpia octoflora), and scarlet globemallow.[15][45] Grazing by black-tailed prairie dogs may also improve the nutritional qualities of some plants.[20][45] On a shortgrass prairie near Fort Collins, Colorado, plant species diversity was greater inside black-tailed prairie dog colonies than outside of colonies, and perennial grasses such as buffalo grass and forbs increased.[15] While black-tailed prairie dog colonies at Wind Cave National Park typically had lower levels of plant biomass and were dominated by forbs, plants growing on prairie dog colonies had higher leaf nitrogen concentrations than plants in mixed-grass prairie outside colonies. Foraging by black-tailed prairie dogs does not significantly affect steer weights.[24][44] While forage availability and use by cattle decreased in black-tailed prairie dog foraging areas, steer weight was not reduced significantly in either of two years of study at the USDA's Southern Great Plains Experimental Range near Woodward, Oklahoma. Nutrient cycling, increased soil fertility, and subsequent changes in forage quality partly compensated for reduced forage availability.[44]
Black-tailed prairie dogs were the most common prairie dog species collected in the wild for sale as exotic pets, until this trade was banned in 2003 by the United States federal government. Prairie dogs in captivity at the time of the ban are allowed to be possessed under a grandfather clause, but no more may be caught, traded, or sold, and transport is only permitted to and from a veterinarian under proper quarantine procedures. The ban was officially lifted on September 8, 2008.[49]
This article incorporates public domain material from Cynomys ludovicianus. United States Department of Agriculture.
The black-tailed prairie dog (Cynomys ludovicianus) is a rodent of the family Sciuridae found in the Great Plains of North America from about the United States-Canada border to the United States-Mexico border. Unlike some other prairie dogs, these animals do not truly hibernate. The black-tailed prairie dog can be seen above ground in midwinter. A black-tailed prairie dog town in Texas was reported to cover 25,000 sq mi (64,000 km2) and included 400,000,000 individuals. Prior to habitat destruction, the species may have been the most abundant prairie dog in central North America. It was one of two prairie dogs described by the Lewis and Clark Expedition in the journals and diaries of their expedition.