Pallid bat (Antrozous pallidus) COSEWIC assessment and status report: chapter 4
Distribution
No evidence has been presented after 1988 to suggest that A. pallidus range in Canada or the United States has changed since that time, although field study in the Okanagan Valley by Collard and Grindal, Chapman and McGuiness, and Barclay and his students after 1988 provides convincing evidence that a resident population exists in south-central B.C. No evidence is available to suggest that these animals are isolated from pallid bat populations in Washington State to the south and the remainder of the species’ North American range, which is presented in Figure 1.
Locations of recorded occurrences of A. pallidus are provided in Figure 2. A. pallidus captures or recovered specimens have been confirmed only 28 times since the species was first reported in the southern Okanagan Valley in 1931. The size of the distributional area in Canada is difficult to estimate because some areas have received more survey attention than others, but is likely between 150 and 500 km².
The majority of pallid bat captures have occurred between Vaseux Lake and Osoyoos, especially on the Inkaneep Indian Reserve which may be due to the fact that, traditionally, the Reserve has been subject to less development than the Okanagan region as a whole (Chapman et al. 1994), though no direct evidence exists to support this hypothesis. Based on compilations of visual observation, directive calls (which are audible to human observers and serve as social contact calls between individuals (Brown 1976)), and captures (6 reproductively active males and 1 non-reproductive male) in 1991, Chapman et al. (1994) estimated that a minimum of 12 animals were resident on the Inkaneep Reserve. Interestingly, their surveys of the neighbouring Similkameen River valley for spotted bats (Euderma maculatum) yielded no captures, sightings, or directive call counts for A. pallidus, although this work is likely insufficient to verify, conclusively, the absence of pallid bats from the Similkameen Valley (Brigham, personal communication). The absence of high quality foraging and breeding area in the Similkameen, as determined by a recent B.C. environment habitat evaluation model (Robertson 1998; Figure 3; and see below), however, may be a contributing factor.
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