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North Dakota's

Federally Listed Endangered, Threatened, and Candidate Species – 1995


Pale Townsend's Big-eared Bat (Plecotus townsendii pallescens)

GIF -- species photo gif--species map

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Status: Former Candidate (Note: As of February 28, 1996, this species is no longer listed as a Candidate species. However, it remains a species of management concern.)

Historical Status:
The pale townsend's big-eared bat historical range is believed to be similar to its present range, however, throughout its range its abundance and distribution is suspected to be in decline.

Present Status:
The pale townsend's big-eared bat is widespread but rare in the Great Plains and northern Rocky Mountains. In the Snake River Plain in Idaho, the abundance and distribution of this bat was documented to have declined substantially in the 1980's. In Montana, extensive surveys have found only 4 maternal colonies and less than 12 hibenacula (place of hibernation).

Habitat:
The pale townsend's big-eared bat is a cave dwelling species and occurs in a variety of habitats, typically shrub-steppe or forest edge. In the warm months, these bats roosts in caves, mineshafts, rocky outcrops, and occasionally in buildings. This bat seldom leaves these roosts until afler dark and thus rarely is observed in flight. They hang from an open ceiling and frequently hang by one foot. During the winter months they hibernate in caves or mines, singly or in small groups. Even in cold weather these bats often move between caves. During hibernation, the bats ears are folded on the back like a ram's horns but if the bats are disturbed, the ears unfold and move in circles like antennae. In spring, female bats will form nursery colonies up to 1000 individuals. Males and barren females generally are solitary in the warm months.

Life History:
This sub-species remains throughout the year in the Northem Plains and appears to be a relatively sedentary species. No long distance migrations have been reported. The pale townsend's big-eared bat also exhibits a high degree of site attachment, returning year after year to the same maternity roosts. The breeding season extends from October to February, just before or during hibernation. The period of gestation is uncertain (up to 100 days reported). A single young is born in late June or July.

Aid to identification:
A medium-sized, pale brownish bat with tremendously enlarged ears (1 1/4 to 1 1/2") extending to middle of body when laid back, the pale townsend's big-eared bat resembles only its relative Rafinesque's big-eared bat, Plecotus rafinesquii. The pale townsend's big-eared bat has two large lumps on its snout and its wings and the tail membrane are hairless. Total length, 3 1/2-4 3/8" (89-110 mm); tail 1 3/8-2 1/8" (35-54 mm); hind foot, 3/8-1/2" (10-13 mm); forearm, 1 1/2-1 7/8" (39-47 mm); weight, 1/4-3/8oz.(9-12 g).

Reasons for decline:
As with other Plecotus species, their habit of hanging fairly exposed in both their hibernacula and maternal colonies makes them vulnerable to disturbance and leading to abandonment and increased mortality. Local extinctions can result in areas with limited roost habitat or excessive disturbance. Pesticides and other environmental contaminants destroy the prey base. Bats are also known for loading of pesticides in their fat reserves.

Recommendations:
Notify a natural resources agency of any suspected pale townsend's big-eared bat sightings.

Comments:
The name townsendii is in honor of an early American naturalist J.K. Townsend (1805-51).

References:
Bats of America by R. Barbour and W. Davis, 1969.
Mammals of the Northern Great Plains by J. Knox Jones, Jr. et. al, 1983.


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