Townsend’s Big-eared Bat
This vulnerable species is very sensitive to human disturbance.
Ministry of Environment, Lands and Parks In view of its apparently small prov- on the Red List, which are being consid- incial population size, vulnerability to ered for legal designation as Threatened disturbance and low reproductive rate, or Endangered. Like other bats, this the future of this little-known bat in species receives general protection Why are Townsend’s British Columbia is indeed uncertain. against harassment, killing or posses- Big-eared Bats at risk? sion under the British Columbia Wild- ownsend’s Big-eared Bats are at risk What is their status? life Act. However, most habitats used by because they are confined to small ownsend’s Big-eared Bats have a these valuable animals do not currently regions of suitable habitat at low ele- broad distribution, including most receive any effective protection. T vations in the southern part of of Mexico and the Western United British Columbia – precisely the areas T States. However, populations are What do they look like? that humans prefer to occupy. Also declining in many areas and the species ownsend’s Big-eared Bat – Coryno- known as the Lump-nosed Bat or has been designated as endangered, rhinus (Plecotus) townsendii – is eas- Western Big-eared Bat, this species is threatened or of special concern ily distinguished from other British sparsely distributed across its range. throughout most of its range. In T Columbia bats by its enormous ears, Townsend’s Big-eared Bats are particu- California, for example, this bat was once which measure about half its body larly vulnerable to disturbance by peo- common, but its numbers have decl- length, and the two fleshy protrusions on ple. Like many other bat species, ined sharply and the its muzzle. These account for its com- in summer they form maternity species is now consid- mon names of “big-eared” or “lump- colonies, often in buildings, and The species ered uncommon. nosed” bat. The fleshy projections on the in winter they gather together to Many known mater- nose, known as pararhinal glands, may hibernate in caves or mines. has been nity colonies in lime- function as sexual scent glands. The large However, when roosting in these designated stone caves in ears of this bat probably have several sites, Townsend’s Big-eared Bats California have been functions, the most important of which do not hide in crevices like many of special abandoned, although is to funnel sounds into the ear canal. bats do and so are very suscepti- concern other maternity sites The ears also have an abundant blood ble to intrusions or vandalism. In exist in mines and supply and assist in the regulation of British Columbia, no hiberna- throughout buildings. At many body temperature. In flight, the ears are tion sites and only one maternity most of its former colony loca- directed forward in plane with the body, colony are protected from tions in Oregon, this leading some researchers to suggest that human entry. Disturbance of range. species is no longer they may also provide lift during flight. females with young can severely found or occurs in Two other British Columbia species, lower breeding success. Repeated distur- reduced numbers. the Spotted and Pallid bats, also have bance at winter hibernacula can cause In British Columbia, only a few very large ears. However, the Spotted energy loss, abandonment of the caves maternity colonies, totalling about 350 Bat is readily distinguished by its promi- and death. bats, have been documented. About 16 nent black and white markings, and Various land use or industrial coastal and interior hibernation sites the Pallid Bat by its lighter colour and activities near bat colonies or in their have been discovered, but 14 of these ears that are not joined at their bases. foraging areas can adversely affect had 6 or fewer bats when surveyed and In addition, the Spotted and Pallid Townsend’s Big-eared Bat. Insecticide the largest colony numbered only 48; bats are both larger than Townsend’s spraying on agricultural or forest our total known winter population is Big-eared Bat. lands is of particular concern, because less than 100 bats. Although additional The long fur on the back of Town- it destroys the bat’s food supply. undiscovered colonies probably exist, send’s Big-eared Bat varies from pale Like other bats, this species has a the total provincial population of this brown to blackish-grey, while the hairs very low reproductive rate. Females bat is likely very small. in the underfur are paler. Male and bear only one young per year. Thus, In view of the rarity and vulnera- female big-eared bats have similar even low rates of mortality caused by bility of Townsend’s Big-eared Bat, it colouring. Bats from coastal areas tend people, when added to natural losses has been placed on British Columbia’s to be darker than bats from the interi- can result in population declines and Blue List. Blue-listed species are con- or of the province. The tragus or ear- eventual elimination of local colonies. sidered vulnerable, in contrast to those let, an erect fleshy structure found at are good for mother bats and their young. Delayed fertilisation occurs in most bats that live in north-temperate areas. Bats are the only mammals that employ this reproductive strategy. In spring, the pregnant females move to summer maternity colonies that are usually within a few kilometres of the hibernaculum. They show great site fidelity, returning to the same loca- tion each year. Here, the young bats, naked at birth, are born and nursed. During summer, the males do not associate with the maternity colonies and are believed to roost singly in scat- tered locations. They play no part in raising the young. In the United States, nursery col- onies typically contain 50 to 150 bats and are found in mine shafts, caves or buildings. The known maternity sites in British Columbia – located in attics, barns and a military bunker – house 25 to 100 bats. Buildings may be the base of the ear in all bats, is about hibernating colonies, which include preferred in British Columbia because one-third of the ear length and point- both sexes, the bats usually hang singly bats need warm sites to promote devel- ed in this species. or in small groups from cave walls or opment of their young and caves here Compared to other British Columbia roofs. When in a state of hibernation may be too cold. bats – which have wing-spans ranging or torpor (a short-term, hibernation- The gestation period of Townsend’s from about 22 centimetres in the dimin- like state) the ears are coiled like a Big-eared Bat is a utive California Myotis to 40 cm in the ram’s horn, the wings are folded In variable 56 to 100 Hoary Bat – Townsend’s Big-eared Bat and the fur is erected to give max- days, depending on is a medium-size species. It has a wing- imum insulation. maternity the temperature in span of about 30 cm, a total length of colonies the the maternity site. 10 cm and a weight of 8½ grams, only How do they reproduce? Cold temperatures 1½ g more than a one-dollar coin. The ownsend’s Big-eared Bats mate females cause torpor in preg- surface area of a Townsend’s Big-eared in autumn and early winter at form tight nant females, which Bat’s wings is large relative to its body their hibernation sites, the only slows foetal devel- weight. This gives these bats an excep- T place where the two sexes com- clusters to opment. Only a tional capacity for manoeuvrable flight monly occur together. Breeding is preserve single offspring is and the ability to fly at low speeds and accompanied by ritualistic vocali- produced by each to hover. Straight-line flight speeds of sations and head nuzzling. Sperm body heat. female, but usually about 3 to 6 metres per second have is stored all winter in the female 90 to 100 percent been reported. reproductive tract, and ovulation and of the females produce young. Births Like all bats, Townsend’s Big-eared fertilisation do not occur until spring. in British Columbia are believed to Bats have five claws on each hind foot, With this unusual strategy, called delayed occur from late June to mid July. The which they use to hang head-down fertilisation, mating takes place when the young bats are large at birth: 25 per- when roosting. In maternity colonies, adults are in peak physical condition, but cent of the weight of the adults! They the females form one or more tight pups are not born until early the next grow extremely fast and are capable of clusters to preserve body heat. In summer when foraging conditions flight at a remarkable 2½ to 3 weeks of age. They reach adult size in one used to locate the insects on which it Present range of month and are weaned at about 6 feeds. It is able to emit echolocation Townsend’s Big-eared weeks. After the maternity colonies pulses through its nose almost as well as Bat in Canada and the United States break up around August and the from its mouth, an unusual trait in bats. newly independent pups begin learn- The low intensity sounds this bat ing to forage for themselves, natural produces enable it to locate and “glean” mortality of young bats is high. insects from vegetation or other sur- Hibernation is another challenge; faces, although most insects are proba- probably only 40 to 50 percent sur- bly captured in the air. Gleaning behav- vive their first winter. Natural death iour may allow Townsend’s Big-eared rates among adults are relatively low, Bat to take advantage of forest habi- with some living at least 16 years. tats that are not used by some less Young females of Townsend’s Big- manoeuvrable species. eared Bat breed in their first autumn; Habitat selection by foraging big- males not until the following year. eared bats has not been studied in British Columbia. Elsewhere, howev- er, the most important foraging habi- tats for this species include insect-rich riparian zones, as well as wetlands, forest edges and open woodland.
What makes them unique? s a group, bats are among the most unusual of all mammals. Although 16 species of this remarkable group, they suckle their young and have more than any other province in Ahair, the similarity to bears, moose Canada. or whales ends there. An ancient but Since Townsend’s Big-eared Bat successful group, over 1000 species of is a relatively sedentary species, bats have evolved over the past 60 mil- staying year-round within a radius What do they eat? lion years and they inhabit all conti- of about 20 to 30 kilometres, British he diet of Townsend’s Big-eared Bat nents except Antarctica. The only Columbia’s small populations are has not been studied in British mammals to have mastered true flight, resident here year round. Although it Columbia, but it is likely to be sim- they vary in size from the two-gram is a social species and forms colonies, T ilar to the diet in the United States, Hog-nosed Bat of Thailand to the these groups are small compared to where small moths about 3 to 10 mil- Gigantic Flying those of most Present range of Townsend’s Big-eared Bat limetres long are the major prey. Other Foxes of southeast in British Columbia other colonial insects eaten include lacewings, dung Asia with wing- bats. This bat is beetles, flies and sawflies. A late flyer, spans up to two primarily a cave this bat emerges just after dark, feeds metres. Bats occu- and mine dweller several times during the night and py almost every throughout its returns to its day roost just before kind of tropical, range, but also dawn. Temporary night-roosts are used subtropical and occupies build- between bouts of foraging. Nursing temperate habitat ings and likely females leave their young in the mater- and have evolved Kamloops uses large trees nity colony when they are foraging. strategies to feed on as well. This species has a sophisticated insects, frogs, fish, At the lati- echolocation system and an exception- fruit, pollen, nectar and even on tude of British Columbia, the ability al ability to detect and avoid objects, other mammals and blood. Some are to hibernate is crucial for resident including mist nets used by researchers important pollinators of flowers. bats, because insects are not active in to catch bats alive. This sonar is also British Columbia is fortunate to have winter. Before entering hibernation these bats accumulate an additional remarkable ability to change their body Valley. In the Interior, most records of 40 percent of their summer weight in temperature within minutes. this bat are from the Okanagan, the form of fat to use as energy Shuswap, Kamloops, Williams Lake through the winter. Hibernation sites Where do they live? and Kootenay areas. Its general pref- are carefully selected on the basis ownsend’s Big-eared Bat occurs erence seems to be for regions that of their temperature and humidity. only in North America, where it are relatively warm and dry in summer The best hibernacula for Townsend’s ranges from southern Mexico to and not extremely cold in winter. Big-eared Bats are caves or mines T southern British Columbia in the This includes the Coastal Douglas- with a relatively constant temperature west, and eastward to South Dakota, fir, Bunchgrass, Ponderosa Pine and of 4 to 10°C, although studies in Kansas and Texas. Isolated populations Interior Douglas-fir zones. British Columbia have shown that occur in limestone regions in the Wintering big-eared bats have been temperatures down to found in caves or mines -7°C may be tolerated in the Gulf Islands, in the for short periods. Dur- South Okanagan Valley, ing hibernation, body at Kamloops Lake and temperature drops to along the Fraser River near that of the cave and near Williams Lake. The heart rate drops from summer nursery sites of over 100 to around 5 beats bats from these locations per minute. Buildings remain unknown. Like- here are not suitable for wise, hibernation sites of hibernation because they the few known maternity do not have constant, colonies have not been cool temperatures. discovered. Much more During hibernation, research is needed to find Townsend’s Big-eared out where these bats live. Bats may lose more than half their autumn What can we do? weight, a more extreme n British Columbia, loss than in most other Townsend’s Big-eared bats. This species rouses Bat is rare and poorly readily from hiberna- . Maarten Vonhof photo Iknown. There is a tion in response to tem- major need for more perature change or disturbance and eastern states. It tolerates environmental complete inventory information so will change its location in the cave or conditions that vary from moist coastal that sites used by these vulnerable bats, even move to another cave in mid- forest to semi-desert scrublands, but its particularly hibernation and maternity winter. Hibernating individuals can fly distribution in North America is proba- colonies, can be adequately protected. with-in 20 to 30 minutes of arousal, at bly determined more by the presence of Although inventory of some caves and a body temperature of 28 to 30°C. cave-rich terrain than by the kind of mines in southern British Columbia has Arousal and movement during winter vegetation in the area. Locally, riparian been carried out, many others have not consumes a lot of stored energy and habitats, wetlands and other moist been searched. Local naturalists and contributes to weight loss, making it places are important foraging sites for cavers can be a great help during this more difficult for bats to survive Townsend’s Big-eared Bat. kind of inventory work. the winter. In British Columbia, the species has Heightened awareness of the charac- In British Columbia, Townsend’s been found from Vancouver Island east teristics and status of Townsend’s Big- Big-eared Bats have been found in to Cranbrook, and north to Williams eared Bat, and bats in general, is needed winter roosts between late September Lake. On the coast it is most common so that more observations of them by and May. They may also enter a along the east coast of Vancouver the public are accurately reported. state of temporary torpor during Island south of Campbell River, but Greater awareness would also reduce the cool summer nights, showing a records also exist for the lower Fraser fear that many people have of bats. . Mitchell Firman photo
’ - . . . William Rainey photo Mitchell Firman photo Mitchell Firman photo
Government agencies, universities and not to disturb maternity colonies. learn more about these fascinating and conservation groups have already Placement of Townsend’s Big-eared members of British Columbia’s fauna. taken some steps to promote the Bat on the provincial Blue List ensures People with bats on their premises conservation of Townsend’s Big-eared that this species will get increased atten- should report this information to the Bat. These include summer mist-netting tion in wildlife conservation pro- nearest BC Wildlife Branch office. For surveys, preliminary cave and mine grams. Nevertheless, much remains many bat species, including Town- inventories, research at one bat cave to be done. send’s Big-eared Bat, there are few and the preparation of a status report Members of the public are encour- provincial locality records and any for the species in British Columbia. In aged to become more tolerant of bats, new records are a valuable scientific the Gulf Islands, where the largest which are generally harmless, and to contribution. known British Columbia wintering colony occurs, land surrounding the cave has been purchased by the British ’ - , : Columbia Nature Trust and assigned Wildlife Branch to the Ministry of Environment, Lands Ministry of Environment, Lands and Parks and Parks for management purposes. PO Box 9374, Stn Prov Govt The Ministry has prepared a man- Victoria, British Columbia V8W 9M4 agement plan that includes provi- sions for control of public access to this relatively well-known site. Simi- lar approaches are needed at other colonies. The entrances of many California bat caves have been gated so that bats can pass through but peo- ple cannot. In British Colum-bia, this approach is being considered for known bat caves and has been success- fully instituted at one maternity colony --- . in a military bunker. People are urged . , not to enter known hibernation caves between September and May Printed in British Columbia on recycled paper with vegetable inks ..