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Data logging of body temperatures provides precise information on phenology of reproductive events in a free-living arctic hibernator

TitleData logging of body temperatures provides precise information on phenology of reproductive events in a free-living arctic hibernator
Publication TypeJournal Article
Year of Publication2011
AuthorsWilliams, CT, Sheriff, MJ, Schmutz, JA, Kohl, F, Toien, O, Buck, LC, Barnes, BM
JournalJournal of Comparative Physiology B
Volume181
Pagination1101–1109
Abstract

Precise measures of phenology are critical tounderstanding how animals organize their annual cycles andhow individuals and populations respond to climate-inducedchanges in physical and ecological stressors. We show thatpatterns of core body temperature (Tb) can be used to preciselydetermine the timing of key seasonal events includinghibernation, mating and parturition, and immergence andemergence from the hibernacula in free-living arctic groundsquirrels (Urocitellus parryii). Using temperature loggersthat recorded Tb every 20 min for up to 18 months, wemonitored core Tb from three females that subsequently gavebirth in captivity and from 66 female and 57 male groundsquirrels free-living in the northern foothills of the BrooksRange Alaska. In addition, dates of emergence from hibernationwere visually confirmed for four free-living malesquirrels. Average Tb in captive females decreased by0.5–1.0C during gestation and abruptly increased by1–1.5C on the day of parturition. In free-living females,similar shifts in Tb were observed in78% (n = 9) of yearlingsand 94% (n = 31) of adults; females without the shift areassumed not to have given birth. Three of four groundsquirrels for which dates of emergence fromhibernation werevisually confirmed did not exhibit obvious diurnal rhythms inTb until they first emerged onto the surface when Tb patternsbecame diurnal. In free-living males undergoing reproductivematuration, this pre-emergence euthermic interval averaged20.4 days (n = 56). Tb-loggers represent a cost-effective andlogistically feasible method to precisely investigate the phenologyof reproduction and hibernation in ground squirrels.

DOI10.1007/s00360-011-0593-z
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