The ecological significance of thermoregulatory responses to heat stress shown by two populations of an Australian murid, Rattus fuscipes

Abstract

1. 1. Both populations of Rattus fuscipes thermoregulate well at ambient temperatures below their lower critical temperatures, being assisted by low thermal conductances that vary directly with ambient temperature. 2. 2. All animals remain normothermic when subjected to temperatures within their thermoneutral zones, although they become hyperthermic at higher temperatures. Evaporative cooling is less effective as a means of delaying lethal hyperthermia than in other Australian Rattus species. 3. 3. The two populations of R. fuscipes studied show minor differences in thermoregulatory ability which correlate well with differences in their environments. 4. 4. The absence of R. fuscipes from relatively hot parts of northern Australia, whilst being abundant in cooler, southern areas, can be explained in terms of the thermoregulatory physiology of this species.