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

Myotis ciliolabrum (Merriam)
Western Small-Footed Bat; Western Small-Footed Myotis
Family: Vespertilionidae
Species account authors: David Nagorsen and Mark Brigham.
Extracted from the Bats of British Columbia

Photo of species

© Jamie Fenneman  Email the photographer   (Photo ID #11738)

E-Fauna BC Static Map
Distribution of Myotis ciliolabrum 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

The Western Small-footed Myotis is the smallest bat in British Columbia. Its fur colour varies from pale tan to orange-yellow on the back; the underside is paler, almost buff. The black ears, wing and tail membranes, face and snout contrast strikingly with the pale fur. The length of the naked area on the snout is about one and a half times the width across the nostrils. The ears are relatively long; the tragus is long and narrow. There is a distinct keel on the calcar; the foot is small. The skull is very small and delicate with a gradually sloping forehead.

Identification

This species is smaller than the Fringed Myotis (Myotis thysanodes) and the Long-legged Myotis (Myotis volans). Its small foot and presence of a prominent keel on the calcar distinguishes it from the Western Long-eared Myotis (Myotis evotis), Little Brown Myotis (Myotis lucifugus) and Yuma Myotis (Myotis yumanensis). The California Myotis (Myotis californicus) is similar in size and possesses a keeled calcar; see that species account for distinguishing traits.

Dental Formula

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

Measurements

total length: 83 (72-90) n = 44
tail vertebrae: 38 (32-45) n = 44
hind foot: 7 (6-8) n = 44
ear: 13 (8-15) n=25
tragus: 7 (4-9) n = 24
forearm: 31.8 (28.8-33.4) n = 47
wingspan: 221 (205-245) n = 25
weight: 4.6 (2.8-5.5) n = 23

Biology

Reproduction

Mating probably takes place in autumn before hibernation. Females usually have a single young, although there is a record of twins from South Dakota. In British Columbia, pregnant females have been observed from 21 June to 13 July and nursing females from 13 June to 3 August. This suggests that young are born from mid-June to mid-July. Newborn young weigh about one gram and have a forearm length of 12 millimetres.
Diet

In the Okanagan the Western Small-footed Myotis feeds primarily on caddisflies and also eats other flies, beetles and moths. It hunts over the edge of rocky bluffs and rarely over open water. There are two peaks in feeding activity: between 10:00 and 11:00 pm and between 1:00 and 2:00 am.
Natural History

In summer the Western Small-footed Myotis roosts in cavities in cliffs, boulders, vertical banks, the ground and talus slopes, and under rocks. It prefers small, protected crevices where the environment is dry and hot (27-33°C). Nursery colonies are situated in similar sites (although in California a mixed colony of males and pregnant females was discovered under the wallpaper of an abandoned house). Small caves, abandoned mine adits and buildings serve as night roosts.

The Western Small-footed Myotis hibernates in winter. In Idaho and Montana, it has been found hibernating in caves and abandoned mines where it prefers temperatures of 1.5°-5.5°C. Recent observations indicate that a few individuals overwinter in British Columbia. In the Okanagan and Williams Lake regions, small numbers (1-3) have been found hibernating in caves and mine adits. Western Small-footed Myotis usually hibernate alone, wedging themselves into tight crevices or depressions in the ceiling of the hibernaculum with their undersides pressed against the ceiling and their heads facing outwards. This seems to provide the most stable environment for them.

Habitat


The Western Small-footed Myotis lives near cliffs and rock outcrops in arid valleys and badlands. Its elevational range in British Columbia is from 300 to 850 metres.

Distribution


This species occurs throughout most of western North America, where it ranges from Mexico to southern Canada in Saskatchewan, Alberta and British Columbia. In British Columbia, it occurs in the dry interior valleys as far north as the Chilcotin River and Williams Lake region.

Taxonomy


In Cowan and Guiguet's The Mammals of British Columbia this species was classified as Myotis subulatus; however, in most of the literature the Small-footed Myotis is classified as Myotis leibii. Western forms of the Small-footed Myotis are now treated as a distinct species, Myotis ciliolabrum. All British Columbia populations belong to the subspecies M.c. melanorhinus, a golden-brown race that ranges from Mexico to British Columbia.

Remarks


The Western Small-footed Myotis is on the provincial Blue List. Until recently, most biologists thought that in British Columbia this species was restricted to the Okanagan and Similkameen valleys. However, recent bat survey work in the dry interior has revealed that this bat is more widespread.

Status Information

Origin StatusProvincial StatusBC List
(Red Blue List)
COSEWIC
NativeS2S3BlueNot Listed
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: 2022-01-16 2:03:24 AM]
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