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Spermophilus variegatus has a diploid chromosome number of 38. Twenty-two of the autosomes are metacentric and fourteen are submetacentric. The fundamental number is 72. The X chromosome is metacentric and the Y chromosome is acrocentric. In New Mexico different populations of rock squirrels show plymorphism in serum proteins. In addition, it has been shown that the genetic makeup of two subpopulations at a location in New Mexico are relatively close. This suggests high gene flow, and is logical since there is no physical barrier between subpopulations here.
Rock squirrels experience a seasonal adjustment of solar heat gain without changing their coat coloration or reflectivity. They do this by altering the structural and optical properties of their pelage. The species' fur consists of a dense inner coat with fine, darker hairs and a sparse outer coat with coarse, lighter hairs. The seasonal differences in coats of rock squirrels allow for a much greater solar heat load capture in winter coats than summer coats. The most important factors contributing to the increased heat gain in winter coats are changes in thermal resistance per unit fur depth in the inner coat and changes in individual hair properties. The changes in optical properties of hairs in the winter coat increase forward scattering, decrease backward scattering, and decrease absorptivity, which together improve radiation penetration. The density of guard hairs in winter coats increase by about 34%, contributing to a 21 % increase in radiation interception in the outer coat and a 28% rise in the inner coat. Also, it has been shown that rock squirrels with summer coats significantly raise metabolic heat production with increasing wind speeds.
The ability to change coat properties to reduce heat loads during the hot and dry summer season allows rock squirrels to decrease the amount of water lost to evaporation for heat dissipation. This is a very important adaptation for a diurnal animal that must endure a long summer drought with little drinking water.
Spermophilus varieagatus communicates with others in a variety of ways. Tactile communication is used in courtship behavior and in greeting and recognition between a mother and her young. Siblings also communicate by greeting with nasonasal contact. Familiar individuals often do this to greet each other too. Spermophilus variegatus has scent glands on the dorsum, posterior to the shoulders, that secrete an oily substance with a faint musky odor. This secretion is used to mark objects within a territory, and during the mating season males rub their backs on rocks and trees. Individuals also rub their cheeks against rocks and smell each other around the different gland concentrations.
The most important means of communication in rock squirrels are posture and vocalization. When unfamiliar squirrels meet they often try to assert dominance by posturing their bodies and tails in different threatening displays. When in proximity to a snake, rock squirrels use a different combination of postures, contorting their bodies in an elongate manner and waving thier tails to appear threatening to the potential predator. Spermophilus variegatus is known to make at least five different types of calls. These are used mostly as warnings. It makes long and short alarm calls that consist of chucks and whistles. These are used to locate the direction from which danger is approaching. Whistle alarms are loud and given from within burrows. It makes squeals when it feels pain or is being handled, and growls when it is involved in aggressive encounters. When threatened, it chatters its teeth as a warning.
Communication Channels: visual ; tactile ; acoustic ; chemical
Other Communication Modes: scent marks
Perception Channels: visual ; tactile ; acoustic ; chemical
Presently, rock squirrels are abundant enough throughout their range not to warrant protection.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
Spermophilus variegatus is sometimes considered a pest because it occasionally damages crops. The effect on crops is usually not significant though. Rock squirrels also carry many ectoparasites that are known vectors of tularemia, Rocky Mountain spotted fever, brucellosis, and sylvatic plague.
Negative Impacts: injures humans (carries human disease); crop pest
The rock squirrel is an important disperser of many plant seeds and fruits. It also may have been a source of food for Native Americans.
Positive Impacts: food
Rock squirrels are important plant dispersers. They often gather seeds and nuts and bury them near their den sites. Also, many animals prey upon this species. Rock squirrels may be an important food source for birds of prey, as well as snakes and many others.
Spermophilus variegatus is host to many species of ectoparasites. Lice, larval Diptera, mites, ticks, and fleas are all parasites of rock squirrels. At least nineteen species of flea use the species as a host. Many of these flea species are vectors of the sylvatic plague, and rock squirrels are susceptible to the plague organism (Yersinia pestis) and may serve as reservoirs for the disease. Other ectoparasites are known as vectors of tularemia, brucellosis, and Rocky Mountain spotted fever.
Ecosystem Impact: disperses seeds
The daily activities of S. variegatus consist mostly of foraging and feeding. Rock squirrels forage both in the trees and on the ground. They climb bushes and trees in search of food nearly as well as tree squirrels. Most foraging takes place in the morning, where food ventures last about twelve minutes at a time. As temperatures increase, rock squirrels spend less and less time during each foraging trip. Rock squirrels eat some of their food as they collect it, but often bring it to a lookout point to eat. In addition, rock squirrels collect large numbers of food items in their cheek pouches and bury their bounty in small holes outside their burrows. The cheek pouches of rock squirrels are quite large, and one researcher counted 62 Gambel's oak acorns carried in the pouches of one individual.
A very wide range of food items makes up the diet of rock squirrels. S. variegatus is known to eat green vegetation, fruits, nuts, grains, berries, roots, flowers, cacti, invertebrates, and small vertebrates. Some of the most important plant foods include, oak acorns, wild sumac berries, cherries, wild plums, wild rye, assorted grasses, walnuts, pine nuts, mesquite, juniper berries, currants, cacti, and agaves. The primary invertebrate food items are grasshoppers, beetles, and earthworms. The wild vertebrates that rock squirrels prey on include young wild turkeys (Meleagris gallopavo) and other fowl. In captivity S. variegatus has even eaten a bannertail kangaroo rat (Dipodomys spectabilis).
The diet of rock squirrels changes seasonally depending on availability of food items. Mostly green vegetation is consumed in early spring, berries and and other fruits are consumed in the summer, and grains, seeds, and nuts are eaten in the fall.
Some preliminary research has shown that where rock squirrels feed on pinyon pine (Pinus edulis), they compete for seeds against birds and insects. When insect herbivores were removed from pinyon pines, small mammals (including S. variegatus) consumed more of the seeds.
Animal Foods: birds; mammals; eggs; insects; terrestrial worms
Plant Foods: leaves; roots and tubers; wood, bark, or stems; seeds, grains, and nuts; fruit; flowers
Foraging Behavior: stores or caches food
Primary Diet: omnivore
Rock squirrels (Spermophilus variegatus) range throughout much of the southwestern United States and Mexico. In the U.S. they can be found thoughout Arizona, New Mexico, Colorado, and Utah, and they inhabit much of western Texas, southern Nevada, and the panhandle of Oklahoma. At the western edge of its range, S. variegatus occupies the southeasternmost corner of California. At the northern boundary S. variegatus has even been observed in extreme southern Idaho. In Mexico the range of rock squirrels encompasses much of Pueblo, Colima, Guerrero, Mexico, and Morelos, but they are not found in eastern coastal lowlands.
The former range of S. variegatus was more extensive than its present distribution. Fossil records show that it was present in tar pits near Los Angeles (320 km west of its present range) and in Little Box Elder Cave just west of Douglas, Wyoming (200 km north of its present range).
Biogeographic Regions: nearctic (Native )
As the common name implies, rock squirrels almost always inhabit rocky locations including cliffs, canyon walls, talus slopes, boulder piles, and steep rocky hills. Within the wide range of S. variegatus, the presence of rocky terrain is critical. In places without rocky landscapes, rock squirrels may make use of old buildings and rock walls, as well as other man-made structures. Spermophilus variegatus inhabits a variety of habitat covers, but is most closely associated with upland grasslands and oak savanna. It is usually not found in open plains, deserts, and upper montane forests.
Perhaps the most important habitat features for rock squirrels are those near den sites. Within occupied habitats, den sites are usually placed in oak savanna or riparian areas. Dens are almost always on steeper slopes, closer to washes, and have more potential lookout points. The slope direction that the den faces seems to be important too. In the north, dens are usually placed on south or west-facing slopes so that they will have earlier snow melt in the spring. In the south, dens are usually on north-facing slopes to provide less stressful summer radiation. Den sites have more shade, are closer to shade trees, and closer to oaks. The amount of ground cover is usually less and the woody debris is usually greater at den locations.
The reason that rock squirrels make their dens on steeper slopes is probably related to better drainage in the summer rainy season. Also, the large amounts of woody debris near dens provide good lookout points. The proximity to washes is most likely tied to the more productive nature of these areas and the associated greater food sources.
Range elevation: 0 to 2900 m.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: savanna or grassland ; scrub forest
Other Habitat Features: riparian
Very little is known about the lifespan of S. variegatus. Wild study animals are known to have lived for at least two and a half years.
Average lifespan
Status: captivity: 9.8 years.
Spermophilus variegatus is the largest ground squirrel found in its range and is the largest member of the subgenus Otospermophilus. Its pelage is mottled along its back, grayish brown in front, and grayish black behind. The dorsum carries indistinct wavy markings of brown and black. The underside is usually buff white to pinkish. The head color ranges from light cinnamon to darker brown. The pelage color is highly variable between and within populations and subspecies. Rock squirrels have large heads and large eyes, and the ears extend above the top of the head and are longer than wide. The neck is stout and long for a squirrel and the tail is long and bushy. Overall, S. variegatus more closely resembles typical tree squirrels than typical ground squirrels.
Rock squirrels attain adult body lengths of 430 mm to 540 mm. The tail of S. variegatus is very long for ground squirrels, and may be 73 to 82% of the body length (172 mm to 252 mm) and as much as 44% of the total length. The adult weight of S. variegatus is highly seasonal and closely associated with annual activity cycles. Typical adult body masses are from 600 to 800 grams. The weight cycles of rock squirrels are tied to breeding activities and seasonal hibernation. Adult males and females are significantly lighter during their respective mating periods. In Arizona, males begin attaining heavy weights in early August to prepare for hibernation, whereas females begin putting on reserves later in August. The fact that males begin preparing for hibernation earlier than females may have resulted in early reports that rock squirrels display sexual dimorphism in size, where males are larger than females. However, this is probably not true, and is just merely a consequence of different peaks in breeding times and preparation for hibernation.
Range mass: 600 to 850 g.
Range length: 430 to 540 mm.
Sexual Dimorphism: sexes alike
Other Physical Features: endothermic ; bilateral symmetry
Rock squirrels are preyed upon by many different animals. Snakes, birds of prey, and many other animals all feed on S. variegatus. In addition, people have been known to kill rock squirrels for food and because they are regarded as pests. Rock squirrels are sympatric with venomous snake species almost throughout their range. Because of this, S. variegatus has developed a distinct anti-snake behavior, which is similar to that of California ground squirrels. When close to a snake, a rock squirrel will approach the snake and examine it with a catious elongate posture. It then erects its tail and waves it from side to side and harrasses the snake by throwing debris. Sometimes, a rock squirrel even attacks the snake. Spermophilus variegatus also has the capacity to neutralize rattlesnake venom.
Another anti-predator behavior of S. variegatus is that it often rests, feeds, and sunbathes in trees or on high rocks or stumps. This allows it to look out for potential predators and communicate alarm calls to other individuals. When disturbed, S. variegatus emits a strong musky scent from its anal glands. This is probably some type of defense mechanism.
Known Predators:
Anti-predator Adaptations: cryptic
The mating system of S. variegatus is polygynous and seasonal. In areas where rock squirrels form colonial aggregations, the dominant male of the colony aggressively defends the breeding rights to the females of the colony against any other adult male. Confrontations between males consist of flank-to-flank shoving that escalates into a rolling fight. Agressive encounters often result in individuals being scarred on the head and flanks. Females actively defend the area immediately around their burrows after the mating season.
Males greatly expand their home ranges during the mating season to look for females that are sexually receptive. This happens more in areas where the population of rock squirrels is less dense and less colonial. Courtship is initiated by the male and consists of nasal to nasal contact, followed by the male stroking the female's head with his paws, and then nasoanal contact. If responsive the female usually arches her back and raises her tail. The female resists the male's attempts at mounting and retreats to a burrow while the male chases. Copulation takes place in the burrow. Observations of sub-dominant males attempting to mount females outside of the burrow have been made, but the female resists such efforts.
Mating System: polygynous
The breeding season of rock squirrels is seasonal and the length and time of the breeding season depend on the latitude and altitude of the population. Unlike many other ground squirrels that emerge from hibernation in breeding condition, male rock squirrels become capable of breeding after emergence in the spring. In southeastern Arizona the testes of adult males are in the scrotal position, which indicates breeding capability, from late March until at least early July. Females are in estrus from at least mid-May to mid-June. Lactating females have been observed here in early June to early July, where the peak percentage of females lactating is in early July to late August. Mating in southeastern Arizona lasts about 9 weeks and takes place between mid-April and early July. The mating season is closely associated with the summer rains, so that juveniles will emerge from the dens shortly after the heavy rains have started and increased production of vegetation. This ensures that food for the young will be readily available when they emerge. The breeding season rock squirrels in northern Utah lasts about 4 weeks, and in central Texas it lasts about 6 weeks. In New Mexico courtship behaviors may occur for up to 14 weeks. Longer breeding seasons may be related to lower population densities, where males may have difficulty finding estrous females.
Estimates of the gestation period are around 30 days, and the pre-emergence period is approximated at 8 weeks. In southeastern Arizona, this means that the young emerge sometime between late July and late September. The young nurse for about two months while in the burrow, and begin foraging for food about 3 days after they emerge. At this point they weigh about 100 grams, and continue to gain weight for more than 2 years after birth. Adult females usually have five pair of mammae, but individuals with four pair have been reported. Juvenile rock squirrels remain within their mother's home range and may use the same burrow for as long as 14 weeks after emergence. Individual rock squirrels achieve sexual maturity at different ages in different locations and populations. In New Mexico few individuals become sexually active as yearlings, but in southeastern Arizona around 50% of yearling females lactate, and several successfully wean young. Similarly, yearling males have been observed with descended testes, but their breeding success is not known.
Breeding interval: Rock squirrels most likely breed only once per year, but some observations of two litters have been made
Breeding season: April to August
Range number of offspring: 3 to 9.
Average number of offspring: 4.8.
Average gestation period: 30 days.
Average weaning age: 2 months.
Range age at sexual or reproductive maturity (female): 1 to 2 years.
Range age at sexual or reproductive maturity (male): 1 to 2 years.
Key Reproductive Features: seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
Average birth mass: 7.8 g.
Average gestation period: 30 days.
Average number of offspring: 4.3.
Females actively protect their natal burrows after mating. They ward off both adult males and females. After a gestation period of about 30 days, the female nurses and takes care of her young for about two months. After the young emerge from the natal burrows, females protect them at least until hibernation. Nose touching between the mother and her young is used for greeting and recognition. Female yearlings often remain near their natal burrows and yearling males usually disperse to new areas.
Parental Investment: altricial ; female parental care ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence (Provisioning: Female, Protecting: Female); post-independence association with parents
Otospermophilus variegatus ye una especie de royedor de la familia Sciuridae. Mide 43-53 cm (17-21 pulgaes) de llargu.
Alcuéntrase en Méxicu y nos Estaos Xuníos.
Otospermophilus variegatus ye una especie de royedor de la familia Sciuridae. Mide 43-53 cm (17-21 pulgaes) de llargu.
Der (oder das) Felsenziesel (Otospermophilus variegatus[1], Syn.: Spermophilus variegatus) ist ein Nagetier aus der Familie der Hörnchen (Sciuridae). Er lebt in Nordamerika im Südwesten der Vereinigten Staaten sowie im nördlichen und zentralen Mexiko. In diesem Verbreitungsgebiet ist der Felsenziesel die größte vorkommende Art der Echten Erdhörnchen.
Der Felsenziesel ist die größte Art der Gattung Otospermophilus und die größte der Echten Erdhörnchen in seinem Verbreitungsgebiet. Er erreicht eine Körperlänge von 430 bis 540 Millimetern und wiegt zwischen 600 und 850 Gramm; die Männchen sind etwas größer als die Weibchen. Der Felsenziesel besitzt einen großen Kopf und große Augen. Die Ohren befinden sich an der Oberseite des Kopfes und sind viel länger als breit. Der Hals ist relativ lang und dick. Die vorderen Gliedmaßen sind kürzer als die hinteren.
Der Schwanz ist lang und buschig, jedoch weniger ausgeprägt als bei den Baumhörnchen. Das Fell auf dem Rücken ist schwarz-weiß und blass gelb-braun gemustert. Die Fellfärbung ist jedoch innerhalb und zwischen den Populationen sehr unterschiedlich. Die Unterseite ist unterschiedlich und variiert zwischen gräulich weiß oder rosa gelb-braun und zimtfarbenem gelb-braun. Der Kopf ist gelb-braun bis fast schwarz.
Der Felsenziesel besitzt Überaugenfenster (Foramen supraorbitale) und eine gräuliche Färbung an den Kopfseiten, welche der Ringelschwanzziesel und der Tropische Ziesel nicht haben. Bei diesen sind die Überaugenfenster geschlossen und die Kopfseiten blass orange-braun oder blass gelb-braun. Der Kalifornische Ziesel und der Baja-California-Ziesel haben im Gegensatz zum Felsenziesel weißliche Nackenseiten und Schultern. Des Weiteren ist das Verbreitungsgebiet des Felsenziesels von denen des Kalifornischen und des Baja-California-Ziesels klar abgegrenzt: Ersterer kommt in Kalifornien und Nevada, westlich des Felsenziesels vor und letzterer ist nur in Niederkalifornien (Baja California) zu finden. Außerdem unterscheidet sich der Felsenziesel vom Kalifornischen Ziesel in der Fellfarbe; letzterer ist kleiner und besitzt einen kürzeren Schwanz im Vergleich zur Körperlänge.
Wie der Name vermuten lässt, bevorzugen Felsenziesel Regionen mit felsigem Untergrund. Ist dieser nicht in natürlicher Form vorhanden, halten sich die Tiere vorwiegend bei alten Gebäuden, Steinwänden oder anderen künstlichen Bauten auf. Felsenziesel sind vor allem bei den Wiesen des Hochlandes und in der eichenbewachsenen Prärie (Savanne) anzutreffen. Selten zu finden sind sie in offenen Ebenen, Wüsten und höheren montanen Wäldern. Felsenziesel sind bis in Höhen von 2900 Metern anzutreffen.
Felsenziesel können einzelgängerisch oder in Gruppen leben. In Regionen mit höherer Populationsdichte bilden sie Kolonien, in denen Sozialverhalten beobachtet werden kann, wie beispielsweise die Rolle eines dominanten Männchens oder der gemeinsame Verzehr von Nahrung. In Regionen mit geringerer Populationsdichte ist das Sozialverhalten viel weniger ausgeprägt. Männchen und Weibchen leben getrennt und treten normalerweise nur während der Paarungszeit in Kontakt.
Felsenziesel leben in Höhlen, die sehr häufig an steilen Hängen und in der Nähe von trockenen Flussbetten unter Felsvorsprüngen, Bäumen oder Büschen liegen. Außerdem befinden sich um den Bau oft überdurchschnittlich viele Holzstücke, die als Aussichtspunkte dienen können. Die Eingänge befinden sich in nördlicheren Regionen vor allem an Hängen, die in südliche oder westliche Richtung zeigen, damit im Frühjahr der Schnee eher schmilzt. In südlicheren Regionen befinden sich die Eingänge vorwiegend in nördlicher Richtung, damit im Sommer weniger der starken Sonnenstrahlung in den Bau gelangen kann.
Der Grund dafür, dass Felsenziesel ihre Behausungen an steileren Hängen anlegen, liegt möglicherweise darin, dass diese in der Regenzeit während des Sommers besser entwässert werden. Die Nähe zu trockenen Flussbetten bringt ein größeres Nahrungsangebot.
Der Felsenziesel verbringt die meiste Zeit des Tages, vor allem am Morgen, mit dem Sammeln von Nahrung, die er sowohl auf dem Boden als auch in den Bäumen findet. Einiges wird gleich an der Fundstelle verzehrt. Häufig nehmen sie es zu Aussichtspunkten und fressen es dort. Zusätzlich sammeln sie viel in ihre Backentaschen und vergraben es in kleinen Erdlöchern. Die Backentaschen des Felsenziesels sind sehr groß. In den gefüllten Taschen eines Tieres wurden 62 Eicheln der Gambel-Eiche gezählt.
Der Felsenziesel frisst unter anderem grüne Pflanzen, Früchte, Nüsse, Körner, Beeren, Wurzeln, Blumen, Kakteen, Wirbellose, wie Heuschrecken, Käfer und Regenwürmer, sowie kleine Wirbeltiere, wie junge Truthühner und andere Vögel.
Der Felsenziesel lebt polygyn. Wenn mehrere Tiere in einer Kolonie zusammen leben, verteidigt das dominante Männchen innerhalb der Gruppe in teils heftigen Kämpfen sein Recht, die Weibchen zu begatten. In Regionen, in denen die Population des Felsenziesels geringer ist und die Tiere vorwiegend einzeln leben, vergrößert sich deren Revier während der Paarungszeit erheblich von 0,7 bis 1,6 Hektar auf rund acht Hektar.
Die Länge und der Beginn der Paarungszeit des Felsenziesels hängen von der geographischen Breite und der Höhe ab, in der die Tiere leben. In Südost-Arizona werden die Männchen zwischen Ende März und Anfang Juli fruchtbar, die Weibchen zwischen Mitte Mai und Mitte Juni. Die Paarung findet dort zwischen Mitte April und Anfang Juli statt und hängt wie auch in anderen Regionen von der Regenzeit im Sommer ab. So können die Jungen kurz nach Beginn der Regenzeit, wenn die Vegetation heranwächst und damit auch das Nahrungsangebot besser ist, den Bau verlassen.
Die Paarung dauert in Utah etwa vier Wochen und in Zentral-Texas rund sechs Wochen. In New Mexico kann sie bis zu 14 Wochen dauern. Dabei vollführt das Männchen zunächst mehrere körperliche Rituale mit dem Weibchen. Danach zieht sich das Weibchen in den Bau zurück, während das Männchen jagen geht. Der eigentliche Paarungsakt findet im Bau statt.
Das Weibchen ist etwa 30 Tage trächtig. Es bekommt zwischen drei und neun Junge (durchschnittlich 4,8), die durchschnittlich 7,8 Gramm wiegen. Sie werden etwa zwei Wochen von der Mutter gesäugt und bleiben weitere sechs Wochen im Bau, bevor sie das erste Mal ins Freie begeben. Für etwa drei Tage werden die Jungen, die nun etwa 100 Gramm wiegen, noch von der Mutter ernährt. Die Jungen bleiben im gleichen Revier der Mutter und nutzen deren Bau bis zu 14 Wochen nach dessen erstmaligem Verlassen. Sie sind nach ein bis zwei Jahren fruchtbar.
Natürliche Feinde des Felsenziesels sind neben Greifvögeln und anderen Raubtieren wie Rotluchs, Graufuchs, Waschbär und Silberdachs auch Schlangen. Da Felsenziesel sympatrisch mit Giftschlangen leben, haben sie ein ausgeprägtes Verhalten gegen Schlangen entwickelt. Befindet sich in der Nähe eine Schlange, nähern sie sich ihr und nehmen eine gestreckte Haltung ein. Danach wedeln sie mit dem Schwanz und schleudern Holzstücke oder kleine Steine. Manchmal greifen sie die Schlange auch an. Felsenziesel sind immun gegen das Gift von Klapperschlangen.
Als weitere Maßnahme zur Vermeidung von Feinden nutzt der Felsenziesel zahlreiche Aussichtspunkte wie Felsen oder Baumstümpfe, bei denen auch häufig die Nahrung aufgenommen wird oder sie sich ausruhen. Nähert sich ein Feind, warnen sich die Tiere gegenseitig. Felsenziesel geben einen starken Moschus-Duft aus ihren Analdrüsen ab, wenn sie gestört werden.
Der Felsenziesel ist im Südwesten der Vereinigten Staaten und im nördlichen Teil Mexikos verbreitet. In den USA kommt die Art in den größten Teilen von New Mexico und Arizona bis zum Edwards Plateau und Pecos River (Trans-Pecos-Texas) im Osten und bis nach Kalifornien im Westen vor. Nach Norden ist sie in Colorado, vor allem westlich der Front Range, in den größten Teilen Utahs bis ins östliche Nevada anzutreffen. In Mexiko erstreckt sich das Verbreitungsgebiet nahezu über den gesamten Norden bis ins Mittlere des Landes nach Puebla, Colima, Guerrero, México und Morelos außer das Tiefland im Osten.
Der Felsenziesel ist eine Art der Gattung Otospermophilus innerhalb der Erdhörnchen. Die Erstbeschreibung erfolgte 1777 durch Johann Christian Polycarp Erxleben. Die Gattung wurde lange als Teil der Ziesel und darin innerhalb der Untergattung Otospermophilus eingeordnet, nach einer umfassenden molekularbiologischen Untersuchung[2] wurde diese jedoch als eigenständige Gattung gemeinsam mit mehreren weiteren Gattungen betrachtet.[3][1]
Es gibt acht Unterarten:
Felsenziesel werden manchmal als Plage angesehen, weil sie gelegentlich Feldfrüchte schädigen. Obwohl die Verluste nicht bedeutend waren, wurden sie dafür getötet. Felsenziesel tragen zahlreiche Ektoparasiten, von denen unter anderem Träger von Tularämie, Rocky-Mountains-Fleckfieber und Brucellose bekannt sind. Nach der Roten Liste der IUCN gilt der Felsenziesel als nicht gefährdet.
Der (oder das) Felsenziesel (Otospermophilus variegatus, Syn.: Spermophilus variegatus) ist ein Nagetier aus der Familie der Hörnchen (Sciuridae). Er lebt in Nordamerika im Südwesten der Vereinigten Staaten sowie im nördlichen und zentralen Mexiko. In diesem Verbreitungsgebiet ist der Felsenziesel die größte vorkommende Art der Echten Erdhörnchen.
The rock squirrel (Otospermophilus variegatus) is a species of rodent in the family Sciuridae and is native to Mexico and the Southwestern United States, including southern Nevada, Utah, Colorado, Arizona, New Mexico, West Texas, and the panhandle of Oklahoma.[2]
Rock squirrels are one of the largest members of the family Sciuridae, with adults measuring up to 21 inches (53 cm) in length.[3] In front and on top, the squirrel's coat is a speckled grayish brown; on the rear and bottom, the gray becomes a more mottled brownish-black tone. They have a marked light-colored ring around their eyes and pointed ears that project well above their heads. Rock squirrels have a long, bushy tail with white edges.
Alarm call
at Water Ranch Lake, AZ
The female rock squirrel has two litters a year, with three to nine young in each litter. The first litter is typically born from April to June, while the second is born in August or September. They are active in the early morning and late afternoons when the weather is warm; when very hot, they may estivate. They are social, and live in colonies with several females and one dominant male that fights other mature males to protect the group. Subordinate males lurk at the outer boundaries of the group. Rock squirrels dig burrows with their sharp claws and muscular legs. The burrows provide shelter, safety, living space, and food storage. Burrow systems can be complex and lengthy, as they are enlarged over a period of years. Entrances are usually hidden beneath rocks and can be wider than 3 inches. In the northern reach of their habitat, rock squirrels hibernate during the colder months of the year. In southern areas, rock squirrels may not hibernate at all.[4] They can withstand long periods of time without water, some even up to 100 days. [5] When alarmed, they whistle a short, sharp, oscillating call.
The rock squirrel is predominantly a herbivore, eating mostly leaves, stems, and seeds, and occasionally invertebrates and small vertebrates. They also eat acorns, pine nuts, fruits of native plants, assorted grasses, mesquite, juniper berries, agaves and cacti. The primary invertebrates include grasshoppers, beetles and earthworms and the vertebrates include young wild turkeys and other fowl.[6] The rock squirrel may eat their own kind, scavenging the remains of squirrels that are already dead. Its diet changes with the seasons, accustoming itself to what is available locally.[7]
Rock squirrels forage for its food on a daily basis, by climbing trees and bushes or on the ground. They collect generous amounts of food items in their cheek pouches, which are quite large. One researcher counted 62 Gambel's oak acorns carried in one squirrel's pouch.[6] These foraging trips are generally short-lived, usually only lasting about 12 minutes. Most foraging is done in the morning, to avoid the hotter parts of the day. They eat some of the food right away and bring a significant portion back to a lookout point or burrow, where they can safely consume or store the rest.[8]
A variety of snakes, birds of prey, and other mammals (bobcats, ringtails, gray foxes, raccoons, coyotes, badgers, domestic cats and dogs) prey upon the rock squirrel. Humans have also been known to eat rock squirrels, but can also view them as pests, resulting in lethal and nonlethal removal. The rock squirrel displays a variety of antipredator behaviors. When close to a snake, they make menacing movements and even throw debris at the snake. They often feed, rest, and sunbathe in trees, high rocks, and stumps. This allows them to watch for predators and to communicate alarm calls to other squirrels. They also emit musky scent from their anal glands when disturbed by predators.[2]
Because of their specialized habitat requirements, there's very select states in the US where these creatures can sustain themselves. These squirrels inhabit rocky mountains, canyon walls, cliffs, and steep rocky hills and there's only a few areas within North America with such type of landscape. These squirrels can be found throughout the southern US border along with Mexico in states like California, Arizona, Utah, Colorado, Oklahoma, New Mexico and parts of West Texas. Contrary to popular belief, in Mexico these squirrels are not found eastern coastal lowlands, but they inhabit areas of Jalisco, Guerrero, Mexico, Morelos, Colima and Puebla. In the western edge of the range of these squirrels in the US, they mostly inhabit parts of southeasternmost corners of California, which includes some of the most arid areas in the entire state.
The rock squirrel (Otospermophilus variegatus) is a species of rodent in the family Sciuridae and is native to Mexico and the Southwestern United States, including southern Nevada, Utah, Colorado, Arizona, New Mexico, West Texas, and the panhandle of Oklahoma.
El ardillón de roca, también conocido como ardilla de pedregal, ardilla terrestre, o techalote (Otospermophilus variegatus), [2] es una especie de roedor de la familia Sciuridae. [3] Mide 43-53 cm (17-21 pulgadas) de largo.
Se encuentra en México y en los Estados Unidos. En México se le ha observado en 26 estados del país (las excepciones son: Baja California Sur, Tabasco, Chiapas, Campeche, Quintana Roo y Yucatán). En México, la NOM-059-SEMARNAT-2010 no considera a este mamífero terrestre en sus listas de especies en riesgo; la UICN 2019-1 lo considera como de Preocupación menor. [2]
Se encuentran en México y en los Estados Unidos.
El ardillón de roca, también conocido como ardilla de pedregal, ardilla terrestre, o techalote (Otospermophilus variegatus), es una especie de roedor de la familia Sciuridae. Mide 43-53 cm (17-21 pulgadas) de largo.
Se encuentra en México y en los Estados Unidos. En México se le ha observado en 26 estados del país (las excepciones son: Baja California Sur, Tabasco, Chiapas, Campeche, Quintana Roo y Yucatán). En México, la NOM-059-SEMARNAT-2010 no considera a este mamífero terrestre en sus listas de especies en riesgo; la UICN 2019-1 lo considera como de Preocupación menor.
Spermophilus variegatus Spermophilus generoko animalia da. Karraskarien barruko Xerinae azpifamilia eta Sciuridae familian sailkatuta dago.
Spermophilus variegatus Spermophilus generoko animalia da. Karraskarien barruko Xerinae azpifamilia eta Sciuridae familian sailkatuta dago.
L'écureuil des rochers[1] (Otospermophilus variegatus) est une espèce de rongeurs de la famille des Sciuridés. Elle se trouve au Mexique et dans le sud-ouest des États-Unis (Arizona[2], Nouveau Mexique, est du Texas).
L'écureuil des rochers (Otospermophilus variegatus) est une espèce de rongeurs de la famille des Sciuridés. Elle se trouve au Mexique et dans le sud-ouest des États-Unis (Arizona, Nouveau Mexique, est du Texas).
Il citello delle rocce (Otospermophilus variegatus (Erxleben, 1777),[2] syn.: Spermophilus variegatus) è un roditore della famiglia degli Sciuridi (Sciuridae). Originario dell'America settentrionale, vive negli Stati Uniti sud-occidentali e nelle regioni settentrionali e centrali del Messico. In ogni parte del suo areale è la specie di scoiattolo di terra più grande.
Il citello delle rocce è la specie più grande del genere Otospermophilus e il più grande tra gli scoiattoli di terra che occupano il suo areale. Presenta una lunghezza totale di 430-530 millimetri e pesa tra 600 e 850 grammi; i maschi sono leggermente più grandi delle femmine. Ha testa e occhi grandi; le orecchie, situate sulla parte superiore della testa, sono molto più lunghe che larghe. Il collo è relativamente lungo e spesso. Gli arti anteriori sono più corti di quelli posteriori.
La coda è lunga e folta, ma meno pronunciata di quella degli scoiattoli arboricoli. La pelliccia del dorso è costituita da un miscuglio di peli bianchi, neri e bruno-giallastri chiari. Tuttavia, il colore della pelliccia varia molto da una popolazione all'altra, nonché da individuo a individuo. Le parti inferiori presentano una colorazione diversa, che varia dal bianco-grigiastro o bruno-giallastro rosato al bruno-cannella. La testa va dal bruno-giallastro al quasi nero.
Il citello delle rocce possiede delle aperture nel cranio sopra gli occhi (foramen supraorbitale) e una colorazione grigiastra sui lati della testa, che il citello dalla coda ad anelli e il citello tropicale non hanno. In questi, le aperture sopra gli occhi sono chiuse e i lati della testa sono bruno-arancio chiaro o bruno-giallastro chiaro. Il citello di Beechey e il citello della Bassa California, diversamente dal citello delle rocce, hanno il collo e le spalle biancastri. Inoltre, l'areale del citello delle rocce è nettamente separato da quello del citello di Beechey e del citello della Bassa California: il primo vive in California e Nevada, a ovest del citello delle rocce, e il secondo si trova solo nella Bassa California (Baja California). Inoltre, il citello delle rocce si differenzia dal citello di Beechey per il colore del mantello; quest'ultimo è anche più piccolo e ha una coda più corta rispetto alla lunghezza del corpo.
Come suggerisce il nome, i citelli delle rocce preferiscono le regioni caratterizzate da un substrato roccioso. Se questo non è disponibile in forma naturale, risiedono principalmente nei pressi di vecchi edifici, muri in pietra o altre strutture artificiali. I citelli delle rocce vivono prevalentemente nei prati di altopiano e nelle praterie disseminate di alberi di quercia (savane). Si incontrano di rado in pianure aperte, deserti e foreste montane di alta quota. La specie si spinge fino a 2900 metri di altezza.
I citelli delle rocce possono vivere da soli o in gruppo. Nelle regioni con una maggiore densità di popolazione, formano colonie in cui è possibile osservare comportamenti sociali, come maschi che ricoprono un ruolo dominante o consumo congiunto di cibo. Nelle regioni con una minore densità di popolazione, invece, il comportamento sociale è meno pronunciato. Maschi e femmine vivono separatamente e di solito entrano in contatto solo durante la stagione degli amori.
I citelli delle rocce vivono in tane sotterranee, che molto spesso si trovano su pendii ripidi e vicino a letti di fiumi asciutti sotto affioramenti rocciosi, alberi o cespugli. Inoltre, intorno alla tana vi è spesso un numero superiore alla media di ceppi d'albero che possono fungere da punti di osservazione. Nelle regioni più settentrionali, gli ingressi si trovano principalmente su pendii rivolti a sud o a ovest, in modo che in primavera la neve che li ricopre si sciolga prima. Nelle regioni più meridionali gli ingressi sono rivolti soprattutto a nord, in modo che in estate possa penetrare nella tana una quantità minore della forte radiazione solare.
Forse i citelli delle rocce costruiscono le loro tane su pendii più ripidi perché sono meglio drenati durante la stagione delle piogge estiva. Inoltre, vengono prediletti i siti vicini ai letti di fiumi asciutti perché tali aree offrono una maggiore disponibilità di cibo.
Il citello delle rocce trascorre gran parte della giornata, soprattutto il mattino, a raccogliere cibo, che trova sia a terra che sugli alberi. Una parte viene consumata proprio nel luogo in cui viene trovata. Spesso il cibo viene portato sui posti di vedetta e mangiato lì. Inoltre, una grande quantità di cibo viene immagazzinata nelle tasche guanciali per poi essere seppellita in piccoli fori nel terreno. Le tasche guanciali del citello delle rocce sono molto grandi: in quelle piene di un esemplare furono contate 62 ghiande di quercia di Gambel.
Il citello delle rocce si nutre di piante verdi, frutti, noci, cereali, bacche, radici, fiori, cactus, invertebrati come cavallette, coleotteri e lombrichi, nonché piccoli vertebrati come giovani tacchini e altri uccelli.
Il citello delle rocce è una specie poliginica. Se più animali convivono in una colonia, il maschio dominante all'interno del gruppo difende il suo diritto di accoppiarsi con le femmine in combattimenti talvolta feroci. Nelle regioni in cui il numero di esemplari è più scarso e gli esemplari conducono prevalentemente un'esistenza solitaria, il loro territorio si ingrandisce notevolmente durante la stagione degli amori da 0,7-1,6 ettari a circa otto ettari.
La lunghezza e l'inizio della stagione degli amori del citello delle rocce dipendono dalla latitudine e dall'altitudine a cui vivono gli animali. Nel sud-est dell'Arizona, i maschi diventano fertili tra la fine di marzo e l'inizio di luglio e le femmine tra la metà di maggio e la metà di giugno. Gli accoppiamenti hanno luogo tra la metà di aprile e l'inizio di luglio e, come in altre regioni, dipendono dalla stagione delle piogge estiva. I giovani possono lasciare la tana poco dopo l'inizio della stagione delle piogge, quando la vegetazione cresce rigogliosa e la disponibilità alimentare è maggiore.
La stagione degli amori dura circa quattro settimane nello Utah e circa sei settimane nel Texas centrale. Nel Nuovo Messico può protrarsi anche per 14 settimane. Il maschio esegue prima una sorta di danza di corteggiamento con la femmina. Quindi questa si ritira nella tana, mentre il maschio la insegue. L'atto di accoppiamento vero e proprio avviene all'interno della tana.
La gravidanza dura circa 30 giorni, trascorsi i quali vengono partoriti tra i tre e i nove piccoli (in media 4,8), che pesano in media 7,8 grammi. Vengono allattati dalla madre per circa due settimane e rimangono nella tana per altre sei settimane prima di uscire per la prima volta. I piccoli, che ora pesano circa 100 grammi, vengono ancora nutriti dalla madre per circa tre giorni. Rimangono nello stesso territorio della madre e usano la sua tana fino a 14 settimane dopo averla lasciata per la prima volta. Raggiungono la maturità sessuale dopo un anno o due.
Oltre ai rapaci e a carnivori come la lince rossa, la volpe grigia, il procione e il tasso americano, i principali nemici del citello delle rocce sono i serpenti. Poiché i citelli vivono in simpatria con i serpenti velenosi, hanno sviluppato un comportamento particolare nei confronti dei serpenti. Se c'è un serpente nelle vicinanze, si avvicinano e assumono una posizione allungata. Poi scodinzolano e lanciano pezzi di legno o piccoli sassi. A volte attaccano direttamente il rettile. I citelli delle rocce sono immuni al veleno dei serpenti a sonagli.
Come ulteriore misura per evitare i nemici, il citello delle rocce utilizza numerosi punti di osservazione come rocce o ceppi d'albero, dove spesso mangiano o riposano. Se un nemico si avvicina, gli animali si avvertono a vicenda. I citelli delle rocce emanano un forte odore di muschio dalle loro ghiandole anali quando vengono disturbati.
Il citello delle rocce è molto diffuso negli Stati Uniti sud-occidentali e nel Messico settentrionale. Negli Stati Uniti, la specie si incontra nella maggior parte del Nuovo Messico e dell'Arizona fino all'altopiano di Edwards e al Pecos River (Texas trans-Pecos) a est e fino alla California a ovest. A nord si trova in Colorado, in particolare a ovest della Front Range, e nella maggior parte dello Utah fino al Nevada orientale. In Messico, l'areale si estende su quasi tutte le regioni settentrionali e centrali del paese fino a Puebla, Colima, Guerrero, México e Morelos, fatta eccezione per le pianure a est.
Il citello delle rocce è uno scoiattolo di terra appartenente al genere Otospermophilus. Venne descritto per la prima volta nel 1777 da Johann Christian Polycarp Erxleben. Per lungo tempo è stato classificato, come tutti i citelli, nel genere Spermophilus, seppur all'interno del sottogenere Otospermophilus, ma dopo un'esauriente indagine di biologia molecolare[3] quest'ultimo è stato considerato un genere indipendente, come molti altri ex sottogeneri.[4][2]
Ne esistono otto sottospecie:
I citelli delle rocce a volte sono stati considerati una seccatura perché occasionalmente danneggiano le colture. Sebbene i danni effettuati non fossero significativi, sono stati duramente perseguitati per questo. I citelli sono ospiti di numerosi ectoparassiti e sono noti per essere portatori, tra gli altri, di tularemia, febbre maculosa delle Montagne Rocciose e brucellosi. Sulla lista rossa della IUCN il citello delle rocce figura come «specie a rischio minimo» (Least Concern).
Il citello delle rocce (Otospermophilus variegatus (Erxleben, 1777), syn.: Spermophilus variegatus) è un roditore della famiglia degli Sciuridi (Sciuridae). Originario dell'America settentrionale, vive negli Stati Uniti sud-occidentali e nelle regioni settentrionali e centrali del Messico. In ogni parte del suo areale è la specie di scoiattolo di terra più grande.
바위다람쥐(Otospermophilus variegatus)는 다람쥐과에 속하는 설치류의 일종이다.[2] 멕시코와 미국 남서부의 토착종이다.
다람쥐과에서 가장 큰 종의 하나로 성체가 되면 몸길이가 최대 53cm까지 자란다.[3] 앞면과 윗쪽 바위다람쥐의 털은 얼룩덜룩한 회갈색을 띤다. 뒷면과 아래 쪽의 회색 털은 더 얼룩덜룩란 갈색과 검은색 색조가 된다. 눈 주위에 반점 무늬의 밝은 색 고리가 있고, 귀는 뾰족하며 머리 윗쪽으로 돌출되어 있다. 바위다람쥐는 끝이 흰 긴 붓꼬리를 갖고 있다.
8종의 아종이 알려져 있다.[2]
다음은 2009년 헬겐(Helgen) 등의 연구에 기초한 계통 분류이다.[4]
마멋족 바위다람쥐속
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