Habitat Atlas for Wildlife at Risk
Townsend's Big-eared Bat
Corynorhinus townsendii

• Total length: 10 cm; wingspan: 29 cm.
• Huge ears: 3-4 cm long (about one half of the body length!)
• Weight: 9 grams.
• Long dorsal fur varies from pale brown to blackish-grey; underfur is paler.
• Two prominent glandular swellings on its nose.

Status:

British Columbia Blue List

Special Significance

Townsend's Big-eared Bats are at risk in British Columbia because of their small provincial population size, vulnerability to disturbance and low reproductive rate. Because of their extreme sensitivity to human contact, they should be left undisturbed when roosting or hibernating. Conservation of riparian areas, which support a diversity of insects, is an important factor in helping to ensure the continued survival of most bat species.

Distribution

• In British Columbia, Townsend's Big-eared Bats have been found from Vancouver Island east to Cranbrook, and north to Williams Lake. In the interior, most records of this bat are from the Okanagan, Shuswap, Kamloops, Williams Lake and Kootenay areas.
• Prefers regions that are relatively warm and dry in the summer, and not extremely cold in winter, including the Coastal Douglas Fir, Bunchgrass, Ponderosa Pine and Interior Douglas Fir zones.

Habitat

• Dry grasslands, coniferous and deciduous forests.
• Foraging habitat includes insect-rich riparian areas, wetlands, forest edges and open woodland.
• Summer day and night roosts include caves, old mines and buildings; these locations are also suitable hibernating sites.
• Dependent on close proximity of roosting and foraging sites.
• Summer maternity colonies and hibernation sites are usually within few kilometres.

Reproduction

• Hibernation occurs from September to May.
• Mating takes place from November to February, usually at hibernation sites.
• Sperm is stored all winter in the female reproductive tract, a strategy called delayed fertilization; ovulation and fertilization occurs in spring.
• In spring, females form summer maternity colonies, usually returning to the same site each year; males roost singly at night in scattered locations.
• Gestation period is controlled by temperature and varies from 50 to 100 days; cool temperatures induce torpor (a lowering of body temperature and metabolic rate).
• Female bats give birth to one young per year in late June to mid July.
• Young grow extremely fast and begin to fly at 2.5 to 3 weeks of age and are weaned at about 6 weeks.

Food Habits

• Bats begin foraging an hour or so after dark and feed several times throughout the night.
• Diet consists of small moths, flies, beetles, lacewings and sawflies.
• Prey is gleaned by these agile bats from foliage of trees and shrubs, although most insects are captured in the air.

Interesting Facts

• A Townsend's Big-eared Bat's average lifespan is 16 years; bats may live up to 30 years.
• Highly maneuverable flyer; capable of flying at slow hovering speeds.
• Large ears funnel sound into ear canal, and may also provide lift during flight and assist with temperature regulation.
• Distinctive fleshy protrusions on sides of nose may function as sexual scent glands.
• One of the few bat species known to consistently overwinter in British Columbia.
• By the end of hibernation, a bat may lose more than half of its autumn weight.

References

1. Ministry of Water, Land and Air Protection. 1998. Species at risk brochure: Townsend's Big-eared Bat. Ministry of Water, Land and Air Protection, Victoria, British Columbia
2. Nagorsen, D.W. and R.M. Brigham. 1993. Bats of British Columbia. Royal British Columbia Museum Handbook, Victoria, British Columbia