چکیده :

Escape tactics and optimal refuge use have attracted considerable interest, but the influence of pregnancy

on escape tactics remains understudied. For instance, embryonic sensitivity to environmental

conditions and maternal constraints vary dramatically across pregnancy, and these dynamics should

modulate the costebenefit balance of refuge use. We experimentally studied thermoregulation and

refuge use in pregnant and nonreproductive aspic vipers, Vipera aspis, at different stages of gestation

(first, middle and last third). We determined preferred body temperatures (Tset) in a cost-free environment

to test for fecundity and stage dependencies of maternal Tset. Then, we examined behavioural

responses to repeated simulated predatory attacks. Pregnant females were extremely precise thermoregulators

compared with nonreproductive females, and Tset was independent of litter size or gestation

stage. After simulated attacks, pregnant females limited their time spent in the refuge and thereby their

deviation from Tset. By contrast, nonreproductive females had a greater response to predation exposure

and adjusted their response to risk level. Contrary to our predictions, pregnant females did not vary their

behaviour based on gestation stage, despite increasing physical burden as pregnancy progressed. Overall,

our results illustrate that pregnant females alter their behaviour to benefit their developing embryos

thermally despite risk to themselves (increased exposure). By doing so, however, the female realizes a

benefit by accelerating temperature-sensitive developmental time and thus reducing the duration of

pregnancy and associated physical burden.