Dataset to accompany manuscript: "Ups and downs of fossorial life: migration restlessness and geotaxis may explain overwintering emergence in the Spotted Salamander"

To decide whether to remain underground or to emerge from overwintering, fossorial ectotherms simultaneously process environmental, gravitational, and circannual migratory cues. Here, we provide an experimental framework to study the behaviour of fossorial ectotherms during soil temperature inversion—a phenomenon that marks the transition between winter and spring in the temperate zone—in light of three non-mutually exclusive hypotheses (i.e., thermoregulatory, negative geotaxis, and migration restlessness). Using a vertical thermal gradient mimicking a burrow, we evaluated how temperature selection (Tsel), activity, and vertical position selection differed under simulated soil temperature inversion (contrasting the active vs. overwintering thermal gradients) in the Spotted Salamander (Ambystoma maculatum). Salamanders had different Tsel and activity levels between gradients, but selected similar heights regardless of thermal gradient orientation. Our results suggest that negative geotaxis may explain responses to changes in vertical thermal gradient orientation, with a possible role for migratory restlessness contributing to differences in activity levels. Our work provides behavioural information in an ecologically relevant context, and will benefit those who aim to better understand the biology of fossorial ectotherms.