Overwintering of Columbia spotted frogs in northeastern Oregon
Bull, Evelyn L.
Hayes, Mark P.
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We studied behavior and locations of overwintering Columbia spotted frogs in northeastern Oregon. We monitored 66 radio-tagged frogs as they moved to overwintering sites during 1997-2000. Frogs used a diversity of overwintering sites, but all sites had an aquatic component including ice-covered ponds (44%), partially-frozen ponds (29%), lotic habitats (23%), and temporary backwaters and seeps (4%). The distance between the original point of frog capture in August-September and the overwintering site varied from 15 to 1200 m. Individuals in ponds were active all winter and remained in shallow water within 1 m of the shore. Frogs overwintering in ponds selected microhabitats with significantly higher water temperatures and dissolved oxygen concentrations compared to other locations in the ponds. Movements during the overwintering period appeared to be linked to water temperatures and dissolved oxygen concentrations