Graduate Thesis Or Dissertation

 

Distribution of bats in Southeast Alaska and selection of day-roosts in trees by Keen’s myotis on Prince of Wales Island, Southeast Alaska Public Deposited

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  • We conducted capture and acoustic surveys for bats in six areas along a latitudinal gradient in Southeast Alaska from mid-May to September in 2005 and we continued surveys on Prince of Wales Island from mid-May to September in 2006. We determined the level of effort required to catch each species and documented ranges in morphology and periods of reproduction. We captured little brown myotis, Myotis lucifugus; California myotis, M. californicus; long-legged myotis, M. volans; and Keen’s myotis, M. keenii, and we acoustically detected and sighted the silver-haired bat, Lasionycteris noctivagans. Capture success varied by species, year, and type of capture site. Our surveys support prior research suggesting that the little brown myotis is the most abundant species in the region, although densities appear to be low relative to other parts of its range. California myotis and Keen’s myotis were captured as far north as Juneau. The long-legged myotis was captured on Wrangell and Prince of Wales Islands and the silver-haired bat was detected on Prince of Wales Island. Prince of Wales Island is the southernmost area we sampled and was the only area where all species were detected. Given low rates of detection, all species appear to occur in low densities in Southeast Alaska. Better understanding of population status and trends and examination of habitat ecology and response to forest management in the region is needed to prioritize conservation strategies. The Keen’s myotis is rare and has one of the most limited distributions of any bat species in North America. Understanding gender-specific roosting ecologies of bats at relevant spatial scales is necessary to effectively evaluate the impact of habitat alteration and prioritize conservation efforts for bats in temperate forests. We examined selection of day-roosts in trees by Keen’s myotis from mid-May to September, 2006 on Prince of Wales Island, Southeast Alaska. Our objectives were to 1) examine relationships between and determine relative importance of habitat characteristics on selection of day-roosts at three spatial scales and 2) determine if habitat associations for males and females differed at each scale. We tracked 13 females to 62 roosts in trees and 6 males to 24 roosts in trees. Features at each spatial scale appeared to influence selection of day-roosts by female Keen’s myotis, but associations were strongest at the tree scale and trees used as roosts were primarily large in diameter with structural defects and located in old-growth forests. Trees in plots around roosts of females had large mean diameters and these plots had a high abundance of roost-like trees. Roosts were generally located near to roads and streams and surrounded by landscapes with a high abundance of old-growth and riparian habitat. Associations were evident for male Keen’s myotis at each spatial scale, but associations at the landscape scale were strongest. Male Keen’s myotis exhibited flexibility with the types of roosts they chose, but tree roosts were primarily snags in early to intermediate decay surrounded by a high relative abundance of roost-like trees that were closer to roads and further from riparian habitat. Habitat associations differed between males and females at each spatial scale and differences are likely a reflection of higher energetic constraints associated with reproduction for females. Energetic benefits gained from optimal roosting habitat may be critical for successful reproduction by females. Females primarily roosted in old-growth habitat and we suggest that maintaining structural components characteristic of old growth will promote conservation of Keen’s myotis in Southeast Alaska.
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