Factors influencing Selection of Shelter by Individual Quokkas, Setonix brachyurus (Marsupialia), during Hot Summer Days on Rottnest Island

Abstract

Individual adult quokkas in the field were studied in relation to their choice of shelter sites on hot summer days and to their physiological response to heat stress and physical condition. Metabolic rate, evaporative water loss and rectal temperature were measured under laboratory conditions. The extent to which male quokkas moved to better shelter on hot days is significantly and positively correlated with their metabolic rate at T*a 37°C; movement of females is significantly but negatively correlated with their rectal temperature. It is concluded that individual quokkas moving more frequently to better shelter on hot days (males) were physiologically less able to tolerate heat stress. Indices of physical condition and indicators of health and age were not correlated with movement. It is suggested that physiological variation in quokkas, both between and within sexes, effectively reduces intraspecific competition for a limiting resource (shelter). This expands their realised niche, increasing the carrying capacity of their environment.