Townsend's big-eared bats were previously known as Plecotus townsendii.
Most navigation and perception in this species is guided by echolocation. The large ears of Corynorhinus townsendii reflect the low-frequency echolocation calls they use and their sensitivity to detecting sounds. These bats can swivel their ears to concentrate on a directional or moving source of sound. Echolocation is accomplished by emitting a rapid series of intense sounds in the larynx. Unlike other mammals, whose auditory organs are connected to the skull, bats' auditory organs are surrounded by fatty tissue or sinuses, which helps dampen the conduction of sounds from the larynx. The middle inner-ear muscles contract before each sonar pulse so that the noises produced by the bat don't drown out the sounds that are being received by the ears. Pulses of high-pitched signals are sent out, ranging from several to a couple hundred pulses per second. The pulses only last a few thousandths of a second. Pulse rate, duration, pitch, and frequency vary based on the situation. High frequency sounds (above 20kHz) are the sounds produced for the purposes of echolocation. When foraging, Townsend's big-eared bats use low frequency pulses with longer durations until they locate a meal. When an insect is located, the pulse rate is increased and shortened and the pitch is lowered to help locate the insect more precisely. When the pulse strikes an obstacle, it is reflected back towards to bat, and the bat can determine the size, shape, texture, distance, direction, and movement of an object.
Auditory perception plays an important part in social interaction as well. Low frequency sounds (under 20 kHz) are within the range of human recognition and usually are used for social interactions. These interactions include spacing between individuals in the colony, mother-young interactions, communication, and warning calls. Males, when performing a courtship display, make high pitched twittering noises to their intended mate. Young bats produce unique calls which help their mothers locate them if they become separated in the colony. Studies have shown that over time, the calls of the young evolve into chirping noises, but when a mother heard a recording of the call of her infant that had been made a week earlier, she still responded.
The importance of olfactory signals to Townsend's big-eared bats is unclear. It is probable that scent plays a role in recognizing individuals within a colony as well as mother-infant recognition. It has been shown that acoustic emissions are key in mother-infant associations in Corynorhinus townsendii, especially when the infant might be beyond the range of olfactory reception. Males have been observed scent-marking females before copulation using excretions from the glands on their muzzles.
Communication Channels: visual ; acoustic ; chemical
Other Communication Modes: scent marks
Perception Channels: visual ; tactile ; acoustic ; ultrasound ; echolocation ; chemical
Corynorhinus townsendii is recognized by many sources as a endangered species, although it has a global rank of Apparently Secure. Its low tolerance for human disturbance often causes the entire colony to relocate if it is interrupted, particularly during hibernation. The presence of humans in their environment can be so stressful to big-eared bats that mortality rate might increase as a result of disturbance. As such, many national parks and other protected lands take precautions to prevent the disturbance of any populations present on their land by placing warning signs outside of roost caves or other sites. Some have installed metal gates that bar passage to people but allow the bats to move freely in and out of their caves.
Populations that roost in abandoned mines are threatened by demolition of those mines. Roosting bats are buried alive in the mine shaft. Researchers have taken steps to work with mining companies to ensure that no populations exist before shafts are destroyed, and with populations that do exist, they usually place grates over the entrance to the shaft, similar to those used to protect cave sites. While protection of their roost sites are key, Corynorhinus townsendii also needs protection of the forested areas where they forage. Deforestation represents a real problem for big-eared bats.
Temperate North American bats are now threatened by a fungal disease called “white-nose syndrome.” This disease has devastated eastern North American bat populations at hibernation sites since 2007. The fungus, Geomyces destructans, grows best in cold, humid conditions that are typical of many bat hibernacula. The fungus grows on, and in some cases invades, the bodies of hibernating bats and seems to result in disturbance from hibernation, causing a debilitating loss of important metabolic resources and mass deaths. Mortality rates at some hibernation sites have been as high as 90%. While there are currently no reports of Corynorhinus townsensii mortalities as a result of white-nose syndrome, the disease continues to move westward across North America.
US Federal List: endangered
CITES: no special status
State of Michigan List: no special status
IUCN Red List of Threatened Species: least concern
While it is popular belief that bats are diseased and dangerous animals, this is largely erroneous. Bats can carry rabies and histoplasmosis, which can infect humans and other warm-blooded species, but reports of disease transmission to humans are uncommon. Bacterial, fungal, viral and mycotic agents have all been associated with bats, and they can be a host to many endo- and ecto-parasitic organisms. In 2001, the Center for Disease Control reported that 17.2% of all rabies cases were bats, there are no estimates for the prevalence of rabies within the species Corynorhinus townsendii. Although Corynorhinus townsendii generally does not take up residence near human populations, their presence in human structures can deteriorate the sanitation and the structural quality of the roost site. The accumulation of feces and the presence of parasites and bacteria represent a real health hazard to people who wander into a roost site. However, the greatest problems seem to be the noise the colony produces as well as the inconvenience of accumulated fecal matter.
Negative Impacts: injures humans (carries human disease)
By far the most recognizable benefit humans gain from the presence of Corynorhinus townsendii is pest-control. They are highly effective predators of moths especially. As a result, there is less environmental and agricultural damage due to insects. In some areas they are important predators of destructive gypsy moths (Lymantria dispar).
Positive Impacts: research and education; produces fertilizer; controls pest population
The most common parasites found on Corynorhinus townsendii are parasitic flies from the family Streblidae. These flies are large, yellow, and extremely visible. They use the bats as hosts throughout the year. Another kind of wingless fly has been found on western populations, from the family Nycteribiidae. Mites are common across all populations. Corynorhinus townsendii share roost sites with other species, sometimes, including Rafinesque’s big-eared bats (Corynorhinus rafinesquii) in southern populations, eastern pipistrelles (Perimyotis subflavus), northern long-eared myotis (Myotis septentrionalis), and eastern small-footed myotis (Myotis leibii). Woodrats (Neotoma) are sometimes also found in roosting areas with these bats. Corynorhinus townsendii populations help to control moth populations because they are moth dietary specialists.
Commensal/Parasitic Species:
Townsend's big-eared bats feed almost exclusively on moths (Lepidoptera), but they've also been known to eat beetles (Coleoptera), flies (Diptera) and other small insects. Small moths 3 to 10 mm in length are the most common prey. Western bat populations typically forage in dense foliage, using low frequency signals to pinpoint the location of insects among the branches of trees. Populations in Virginia and Kentucky, however, have been observed foraging among the forest but also in open fields and along low cliff walls. They generally glean prey off the branches of trees and can drink in flight from the surface of ponds and pools. After feeding, they return to night roosts to digest and may make a second foraging trip before dawn. Townsend's big-eared bats are also recognized as one of the most effective "food specialists" in North America, with a diet compromised of over 80% moths. The availability and size of moth populations are significant factors in the sustainability of any population of Corynorhinus townsendii.
Animal Foods: insects
Primary Diet: carnivore (Insectivore )
Corynorhinus townsendii has a broad range in western North America, from southern Canada to southern Mexico. They have significant populations in all Rocky Mountain states (Arizona, Colorado, Utah, Wyoming, Idaho, and Montana) as well as Texas, South Dakota, Kansas, northwest Arkansas and southern Missouri and west through California, Oregon, and Washington. Corynorhinus townsendii townsendii is the subspecies thought to occur mostly in the Pacific Northwest. Corynorhinus townsendii pallescens is a considerably more pale subspecies that inhabits desert habitats. There are isolated populations of the subspecies Corynorhinus townsendii ingens, found in caves in eastern Oklahoma, and Corynorhinus townsendii virginianus, found in east-central Kentucky, West Virginia and westernmost Virginia in the Potomac and James tributary river valleys.
Biogeographic Regions: nearctic (Native )
Most western populations of Corynorhinus townsendii live in montane forest. This type of forest is thick with pine, fir and aspen trees and is bounded by shrub and grasslands. At higher elevations, the surrounding vegetation is subalpine. Corynorhinus townsendii pallescens lives in an arid habitats with limited desert scrub vegetation, but stops short of living in extreme desert environments. Corynorhinus townsendii townsendii inhabit the humid coastal area of the Pacific Northwest. Eastern populations of Corynorhinus townsendii are generally found in oak-hickory forests.
Corynorhinus townsendii individuals choose roosting sites most commonly in caves, cliffs, and rock ledges but have been found in abandoned mines and other man-made structures. Colonies normally choose relatively cold places for roosting, and pick hibernacula with a considerable amount of air movement. Abandoned buildings are usually used only during the summer, while caves and abandoned mines are preferred in the winter.
Roost sites are generally have open ceilings because Townsend's big-eared bats don't crawl well. They prefer habitats that are almost completely dark and are extremely sensitive to human disturbance, which nearly always causes colonies to relocate.
Range elevation: 457 to 2743 m.
Habitat Regions: temperate ; terrestrial
Terrestrial Biomes: forest ; scrub forest ; mountains
Other Habitat Features: caves
Bats have the potential for great longevity. Corynorhinus townsendii individuals have been recorded living over twenty-one years. However, mortality in young is high, averaging 38 to 54%. If the young can survive the first year of life, their chance of survival rises to an average of 80% yearly. It has been noted that the life expectancy of Corynorhinus townsendii is much shorter when kept in captivity.
Range lifespan
Status: wild: 21 (high) years.
Townsend's big-eared bats are medium-sized bats with broad wings. They have two large, fleshy glands on either side of the muzzle. The snout is short with elongated nostril slits. Coloration varies from population to population, although all fur colors tend to be some hue of brown or gray. Hairs are darker at the base than they are at the tips. The dorsum can be anywhere from pale cinnamon brown to blackish brown to slate gray. The ventral side tends to be buff to pale brown. Ears are large, generally more than 25 mm in length and connected by a low band across the forehead. The ears are usually directed forward while in flight. When these bats are sleeping, the ears are generally rolled down and back across the head, resembling ram horns, which gives these bats one of their nicknames, "ram eared bats". Corynorhinus townsendii can range in mass from 5g to 13g.
Dental formula is I 2/3, C 1/1, P 2/3, M 3/3 = 36.
Range mass: 5 to 13 g.
Range length: 90 to 115 mm.
Range wingspan: 297 to 320 mm.
Other Physical Features: endothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes alike
The nocturnal habits of Townsend's big-eared bats, their ability to fly, and their occupation of difficult to access roosting areas, makes them unlikely prey for most predators. Nocturnal birds of prey, snakes, and rats will prey on big-eared bats occasionally. Specific reports of predation include Pacific gopher snakes (Pituophis catenifer catenifer), domestic cats (Felis catus), and raccoons (Procyon lotor). A California study of a colony of Corynorhinus townsendii that had taken up residence in an abandoned multi-story house reported Rattus rattus> preying on the colony and the tracks and markings made by these rodents were discovered in the rafters closest to the roosting site of the bats. Colonies threatened by a predator may use warning vocalizations varying from loud cries to twittering.
Known Predators:
Mature males begin spermatogenesis during summer, reaching its peak in September. Females experience a short proestrus in late summer. Estrus occurs in the fall with copulation taking place from November to February. Townsend's big-eared bats mate with multiple partners repeatedly during the breeding season. Males perform a mating display, during which they approach a female making loud, twittering noises. If they are accepted by the female, the male rubs his snout over the female's face, neck, forearms and ventral surface. The glands on the male's snout serve to scent mark the female prior to copulation, during which the female is usually in a state of torpor. The sperm is stored in the female's reproductive tract until the spring, when ovulation, implantation, and gestation occur.
Mating System: polygynandrous (promiscuous)
Most breeding occurs in the winter months at hibernacula, peaking November through February. Some females are inseminated before their arrival at winter roosts. The normal gestation period is 56 to 100 days, depending on ambient temperatures and length of time the female spends in torpor during gestation. In the spring and summer, females form maternity colonies in caves, mines, and buildings while males live solitarily or in small bachelor clusters. Most females give birth to only one young. Maternity colonies usually break up in August, although females who have lost their young typically leave the roost at an earlier date. After maternity colonies disperse, females migrate to hibernacula and reunite with males. Young females typically mate their first autumn, while males don't mate until after their first year of life.
Breeding interval: Townsend's big-eared bats breed once yearly.
Breeding season: Breeding occurs in the winter, peaking from November through February.
Average number of offspring: 1.
Range gestation period: 56 to 100 days.
Average weaning age: 6 weeks.
Range age at sexual or reproductive maturity (female): 4 (low) months.
Range age at sexual or reproductive maturity (male): 1 (low) years.
Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous ; sperm-storing ; delayed fertilization
The young are born naked and their ears are folded over their unopened eyes for several days after birth. They cling to their mother's bodies during the day and cluster together in groups when the mothers leave at night to feed. Pups are weaned by at least 6 weeks of age and become independent shortly after.
Parental Investment: altricial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Female); pre-independence
Townsend's big-eared bat (Corynorhinus townsendii) is a species of vesper bat.
Townsend's big-eared bat is a medium-sized bat (7-12 g)[2] with extremely long, flexible ears, and small yet noticeable lumps on each side of the snout. Its total length is around 10 cm (4 in.), its tail being around 5 cm (2 in) and its wingspan is about 28 cm (11 in).
The dental formula of Corynorhinus townsendii is 2.1.2.3.3.1.3.3. × 2 = 36[3]
C. townsendii can be found in Canada, Mexico, and United States.[1]
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The mating season for the Townsend's big-eared bat takes place in late fall. As with many other bat species, the female stores sperm in her reproductive tract after mating, and fertilization occurs in the spring. Gestation lasts from 50 to 60 days. As with other bat species, pups are born without the ability to fly. Only one pup is birthed per female.[4] One study found the average lifespan of a Townsend's big-eared bat to be 16 years.[5]
This bat requires large cavities for roosting; these may include abandoned buildings and mines, caves, and basal cavities of trees.[2] During summer, these bats inhabit rocky crevices, caves, and derelict buildings. In winter, they hibernate in a variety of dwellings, including rocky crevices, caves, tunnels, mineshafts, spaces under loose tree bark, hollow trees, and buildings.[6] During the summer, males and females occupy separate roosting sites; males are typically solitary, while females form maternity colonies, where they raise their pups. A maternity colony may range in size from 12 bats to 200, although in the eastern United States, colonies of 1,000 or more have been formed.[2] During the winter, these bats hibernate, often when temperatures are around 32 to 53 °F (around 0 °C to 11.5 °C.) Townsend's roost singly during hibernation, forming small clusters only rarely. Males often hibernate in warmer places than females and are more easily aroused and active in winter than females. The bats are often interrupted from their sleep because they tend to wake up frequently and move around in the cave or move from one cave entirely to another. Before hibernation, C. townsendii individuals increase their body mass to compensate for the food they do not eat during the winter.[2]
This species has 2-3 feeding periods between dark and dawn, with periods of rest in between. They rest in areas different from where they roost during the day.[7]
During tests on straight-line courses, C. townsendii flew at speeds ranging from 2.9 to 5.5 m/s (6.4 to 12.3 mph).[8]
This species is a moth specialist, and may feed almost exclusively on Lepidoptera.[9] However, its diet may include small moths, flies, lacewings, dung beetles, sawflies, and other small insects.[2] As a whisper bat, it echolocates at much lower intensities than other bats, and may be difficult to record using a bat detector. (This may be partly because it specializes on moths --- with some moths having the ability to hear bats, possibly producing their own noises to 'jam' a bat's echolocation in an effort to thwart predation.
C. townsendii, as well as its close relative C. rafinesquii, both have low wing loading, which means a large wing area to mass ratio. This morphology allows for a large amount of lift, high maneuverability, low-speed flight, and hovering during flight.[8]
Their large pinnae are usually in line with the body during flight; this indicates one of the roles of the pinnae is to impart lift during flight. The ears are also used to transmit sound into the bat's external auditory meatus, effectively distinguishing between ambient noise, and the sounds of predators or prey.[8]
Five subspecies are described:[10]
Townsend's big-eared bat (Corynorhinus townsendii) is a species of vesper bat.
