Shifts in Body Temperature and Escape Behaviour of Female Podarcis muralis during Pregnancy

Abstract

Average field body temperatures of pregnant female Podarcis muralis (32.620C) were significantly lower than that of males and non-pregnant females (overall average: 33.740C). However, when tested in terrarium with a strong thermal gradient in a limited space, which represents a low-cost environment for thermoregulation, neither body temperature nor position in the thermal gradient differed among groups of sex and reproductive condition. Body temperatures selected in thermal gradient (overall average: 33.770C) was similar to those exhibited in the field by males and nonpregnant females. This means that low body temperature exhibited by pregnant females in the field is not a consequence of a change of the thermal preferences at this stage, but might be explained on the basis of constraints related to their reproductive condition. Pregnant females stay closer to the refuge and allow approach to a shorter distance than do males and non-pregnant females. Approach distance was partially explained by the distance to refuge, but even when the effects of the distance to refuge were removed by applying the residuals of the regression, the approach distance for pregnant females was significantly lower than for other individuals. This reflects the existence of a behavioural component of motion-less in addition to the tendency to remain closer to a shelter, and means a shift in the predator-avoidance tactic from flight to crypsis, presumably because effectiveness of the flight tactic would be reduced during pregnancy. The behavioural changes associated with pregnancy may preclude careful thermoregulation, as this requires frequent movements