BASAL HOLLOW ROOST SELECTION BY THE TOWNSEND'S BIG-EARED BAT AND OTHER BATS ON THE NORTH COAST OF CALIFORNIA.
Amon J. Armstrong; Humboldt State University; 1882 Golf Course Road, Bayside, CA, 95524; (415) 272-4878; aja40@humboldt.edu; Joseph M. Szewczak
The state of California lists the Townsend's big-eared bat (Corynorhinus townsendii) as a species of special concern because of population declines due mainly to habitat loss and disturbance. This species roosts in open cavity structures, typically caves, throughout the western United States. On the north coast of California, this species and others will roost in basal hollows of trees. Because knowledge of the characteristics of basal hollows and landscape associations that correlate with their use remains limited, we measured 135 tree hollows at 9 sites in Del Norte, Humboldt, and Mendocino counties and collected guano for one year (2017-2018). We used the weight of monthly guano collected in basal hollows as an index of bat use. Species were identified by DNA analysis at Northern Arizona University's  "Species from Feces" lab. In an initial test of 15 guano samples, 47% of bats identified were Townsend's big-eared bats. The top ranked generalized additive model (n = 27 hollows), using tree hollow measurements versus guano mass response, indicated more bat activity in hollows with higher and wider openings and larger enclosures above the opening. Quantifying basal hollow roost preferences will support forest management and conservation practices. This is a graduate project with some analyses forthcoming, therefore is not complete.
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