Euderma maculatum
(Spotted Bat)

Order: Chiroptera
Order Description: Bats
Family Description:

The spotted bat is distinctly colored with a blackish upper fur with patches of white over each shoulder and at the base of the tail. The ears are pinkish, long (over 40mm), and translucent in living individuals. This is the only Idaho species that has an audible echolocating call within the range of human hearing.

Euderma occur in British Columbia west to South Dakota, south to Mexico and west through California to southern Oregon. The distribution of populations is highly spotty, likely as a result of the habitat requirements of this species. In Idaho, populations occur in the south western corner of the state. An unvouchered capture along the Salmon River in Nez Perce County exists. Two voucher specimens have been collected in Idaho.

Found, up to 2450 m, in various habitats from desert to montane coniferous Click word for definitionforests. In Idaho, recently observed in canyons of Owyhee County.

Spotted bats have been collected in desert pinion-juniper woodlands near sandstone cliffs or over streams and water holes in coniferous forests with rock cliffs nearby. Individuals normally roost Click word for definitionin deep rock crevices of canyon and cliff walls but specific roost characteristics are not well documented. Two cave sightings have been reported, but likely represent unusual conditions that led to temporary use. The first specimen collected in Idaho was found under a tree in Canyon County.

Insectivorous Click word for definition; feeds primarily on noctuid moths.

Apparently relatively solitary but may hibernate Click word for definitionin small clusters; winter habits are poorly known. Roosts in cracks and crevices in cliffs and canyons. British Columbia study found individuals used same roost Click word for definitioneach night from May-July, but not after early August. Individuals roosted solitarily during active season, appeared to maintain exclusive foraging areas, and foraged up to 6-10 km from day roost each night. Species forages primarily over dry, open coniferous Click word for definitionforest. In western Texas study, nearly all individuals netted were caught after midnight. In British Columbia study, individuals left day roost an average of 49 min after sunset (13 min in radio-tagged bats), and returned an average of 67 min before sunrise; foraging activity peaked at 0000-0300 hr (emergence from day roost was not significantly influenced by moonlight). Individuals flew continuously (5-15 m above ground) between departure from and return to day roost; foraging areas of different individuals overlapped. Spotted bat calls can be detected by the human ear. Species is very sensitive to human disturbance.

Foraging activity in this bat seems to vary geographically, but often occurs over wet meadows. In British Columbia, individuals exited their roost approximately one hour after sunset and returned shortly before sunrise. In Texas, individuals apparently either exit later or drink water late as they are netted after midnight, a situation also observed in Oregon. Some research suggests this bat maintains exclusive foraging areas but tolerates overlap by other individuals while foraging. Fewer than one hundred specimens of this bat exist in museums. As a result of rarity, most netted individuals are immediately released by individuals conducting surveys.

Following delayed fertilization Click word for definitionand implantation Click word for definition, births apparently occur in late May or early June in southern range, possibly later in north. Female probably produces 1 young.

Status: Unprotected nongame species
Global Rank: G4
State Rank: S2

Important State References:
Keller, B.L. 1987. Analysis of the bat species present in Idaho, with special attention to the spotted bat, Euderma maculatum. Dept. Biol. Sciences, Idaho St. Univ., Pocatello. 25pp.

Information written by Barry Keller,© 2000
Map image provided by
Stephen Burton,© 2000
Design by Ean Harker©1999, 2000.