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1 August 2007 Day Roosts of Female Fringed Myotis (Myotis thysanodes) in Xeric Forests of the Pacific Northwest
Michael J. Lacki, Michael D. Baker
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We radiotracked 25 adult female fringed myotis (Myotis thysanodes) to day roosts in xeric ponderosa pine (Pinus ponderosa) forests on the east side of the Cascade range in Washington and Oregon from 2001 to 2003. Bats were tracked for an average of 9.6 days/bat ± 0.1 SE for a total of 240 roost-days. Bats used 118 roosts, 93% of which were in the crevices of rocks. Pregnant females chose horizontal crevices 58.8% of the time, whereas lactating (60.9%) and postlactating (75%) females selected vertical crevices more often. There was no difference in crevice length or crevice width among roosts in rocks used by pregnant, lactating, and postlactating females. Snags were used as roosts on only 6 occasions, and all were in ponderosa pines situated within a single watershed. The largest emergence count of fringed myotis that we recorded was 118 bats from a ponderosa pine snag. Snags used as roosts were larger in diameter, taller in height, and extended farther above the local canopy than random snags. Bats used the same roost for 1.8 consecutive days ± 0.12 SE and used an average of 5.5 roosts/bat ± 0.69 SE. Bats moved 1.6 km ± 0.34 SE between capture sites and roosts, with distance between successive roosts averaging 0.55 ± 0.12 km. Roosts were 1.4 km ± 0.36 SE from the closest perennial stream. Examination of these data indicates that snags are a less significant component of roosting habitat of fringed myotis in ponderosa pine forests on the east side of the Cascades than has been reported for the species in other regions of its distribution.

Michael J. Lacki and Michael D. Baker "Day Roosts of Female Fringed Myotis (Myotis thysanodes) in Xeric Forests of the Pacific Northwest," Journal of Mammalogy 88(4), 967-973, (1 August 2007).
Accepted: 1 December 2006; Published: 1 August 2007

fringed myotis
Myotis thysanodes
ponderosa pine
rock crevices
roost switching
snag roosts
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