E-Fauna BC: Electronic Atlas of the Wildlife of British Columbia

Euderma maculatum (J.A. Allen)
Pinto Bat; Spotted Bat
Family: Vespertilionidae
Species account authors: David Nagorsen and Mark Brigham.
Extracted from the Bats of British Columbia

Photo of species

© Brock Fenton  Email the photographer   (Photo ID #74381)

E-Fauna BC Static Map
Distribution of Euderma maculatum in British Columbia
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Introduction


The information provided below is extracted from the Bats of British Columbia, and may be dated. Check the status section below for current status information.

Species Information


Click on the image(s) below to view an expanded illustration for this taxon.



Illustration Source: Bats of British Columbia by David Nagorsen and Mark Brigham © Royal BC Museum

Jet black dorsal fur with large white spots on the rump and shoulders make the Spotted Bat one of the most distinct and spectacular bats in North America. It has smaller white patches at the base of each ear and its underside is whitish with black underfur. There is a small, naked patch on its throat, which is often hidden in the fur. The immense pinkish ears are joined at their bases across the forehead; the tragus is large and broad. A fringe of fine hairs extends along the top border on the back of the ears. The calcar is not keeled. The skull has an elongated brain-case with a gradually sloping forehead.

Identification

The conspicuous ears and three White spots on the back distinguish this species from any other British Columbian bat. The combination of 2/3 incisors and 2/2 premolars is also unique among British Columbian bats.

Dental Formula

incisors: 2/3
canines: 1/1
premolars: 2/2
molars: 3/3

Measurements

total length: 116 (107-125) n = 4
tail vertebrae: 50 (47-50) n = 4
hind foot: 10 (9-10) n = 4
ear: 38 (34-41) n = 5
tragus: 13 (13-14) n = 3
forearm: 50.9 (47.9-53.1) n = 9
wingspan: 346 (336-355) n = 5
weight: 17.9 (16.2-21.4) n = 6

Biology

Reproduction

Little information is available on reproduction but the scanty data suggest that mating takes place in autumn. Females produce one young; the only pregnancy record for British Columbia suggests that young are born in late June or early July.
Diet

The Spotted Bat hunts over open Ponderosa Pine forests, hay fields and marshes adjacent to lakes. Every summer it can be found foraging over the marshy area on the west side of Vaseux Lake. It leaves its roost 30 to 60 minutes after sunset. It is a solitary hunter that feeds on moths captured while flying 5 to 15 metres above the ground. Although large ears are often associated with gleaning bats, there is no evidence to suggest that the Spotted Bat is a gleaner. It is quite predictable in its daily movements, usually following a set route to its night-time feeding area and returning to the same roost night after night. It may move as far as 10 kilometres between the day roost and feeding areas.

Its echolocation calls range between 6 and 16 kilohertz, making this our only bat that can be heard without a bat detector, at least by those whose ears are relatively sensitive to high-frequency sounds. The calls resemble a high-pitched, metallic click and could be mistaken for insect sounds by those unfamilar with them. The calls of the Spotted Bat have several important characteristics that affect its natural history. Low-frequency calls should be most effective for detecting larger prey, which is consistent with the evidence suggesting that most of this bat's diet consists of medium-sized moths. Several researchers have suggested that the low-frequency calls enable the Spotted Bat to avoid detection by certain species of moths that can detect the ultrasonic echolocation calls of other bats. Another characteristic of low-frequency sounds is that they can carry for considerable distances through the air - it is suspected that the Spotted Bat can detect its insect prey at long range. The extraordinarily large ears probably help the bat hear the returning echoes of its low-frequency calls.
Natural History

Typically, day roosts are in crevices of steep cliff faces. The most important roosting sites in the Okanagan Valley are located in cliffs at McIntyre Bluff, Gallagher Bluff, Spotted Bluff, the west side of Vaseux Lake and the Vaseux canyon.

The audible echolocation calls make it relatively easy for the biologist or naturalist to monitor the presence and activity of this bat. Even so, the distribution of Spotted Bats in the province is poorly known. The recent discovery of this species in the Thompson, Fraser and Chilcotin valleys indicates that there may be localized populations throughout the dry interior. We strongly encourage local naturalists in this region to familarize themselves with the sounds of this bat and to search for it in their area.

The Spotted Bat has been heard in the Okanagan from early April to late October, but the whereabouts of this population in winter is a mystery. Little is known about the winter biology of this bat throughout its entire range. The only hibernation record for its entire range is of four individuals in a cave in Utah some sixty years ago. Research in southern Utah suggests that this species is occasionally active during mid winter in the western United States. No hibernating individuals have been found in British Columbia. The Spotted Bat may hibernate in crevices in cliffs inaccessible to humans, or it may spend winter outside the province.

Habitat


Throughout western North America the Spotted Bat is associated with arid desert terrain. Its elevational range in British Columbia extends from 300 to 900 metres above sea level, although most occurrences are below 500 metres.

Distribution


This is a rare bat with a discontinuous distribution throughout its range across western North America. Its range includes Mexico, and the United States from Arizona and California to Idaho and Montana. In Canada, the Spotted Bat occurs only in British Columbia where there are localized populations in the dry interior from the southern Okanagan Valley to the Chilcotin River and Williams Lake region.

Taxonomy


No subspecies are recognized.

Remarks


The Spotted Bat is on the provincial Blue List. This mammal was first discovered in British Columbia in 1979 when Brock Fenton and his colleagues detected its echolocation calls near Oliver while conducting a general bat survey in the Okanagan. The pattern of white markings on the Spotted Bat resembles the patterns found on some moths. The significance of these markings is unknown. They could serve as a warning signal to predators, provide camouflage or act as some kind of visual signal in communication, but there is no evidence to support any of these ideas.

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
NativeS3S4BlueSC (Nov 2014)
BC Ministry of Environment: BC Species and Ecosystems Explorer--the authoritative source for conservation information in British Columbia.

Additional Photo Sources

General References


Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. E-Fauna BC: Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab for Advanced Spatial Analysis, Department of Geography, University of British Columbia, Vancouver. [Accessed: 2022-08-18 4:22:12 AM]
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