Activity Patterns and Thermal Biology of the Toad Bufo boreas halophilus

Abstract

An annual model of toad activity patterns and microhabitat selection, and the thermal consequences of such behaviors was composed by observing behavior and body temperatures (Tb's) of unrestrained, undisturbed, adult Bufo boreas halophilus throughout a two year period. The toad's choice of daily and seasonal activity times and it's use of the retreat burrow (a thermally buffered microhabitat) appeared to be the primary factors resulting in a relatively narrow range of toad Tb's (10-25 C) throughout the year. Laboratory-determined preferred body temperatures (PBT) of toads sampled from an outdoor enclosure indicate that toads do not adjust PBT with respect to season, state of activity (active vs dormant), previous exposure to ambient temperature, or endogenous rhythms. Behavioral stenothermy demonstrated by toads tested in a laboratory thermal gradient (pooled :, SD = 24.2 ? 2.95) was not observed in outdoor toads, although mean Tb'S of outdoor toads approximated PBT at all active times except spring nights.