Paternal care reduces maternal hyperthermia in Djungarian hamsters (Phodopus campbelli)

Throughout lactation, maternal body temperature, nest attendance, activity level and reproductive success of solitary female Djungarian hamsters housed at the recommended ambient temperature of 23 degrees C (Canadian Council on Animal Care guidelines) were compared with those of paired females housed at the same temperature and with solitary females housed at the natural burrow temperature of 18 degrees C. As expected, cooler ambient temperature improved pup survival and weaning weight. Likewise, paternal presence largely compensated for the poor pup growth typical at 23 degrees C. However, the mechanisms were not the same. Females at reduced ambient temperatures were as hyperthermic as females at the higher temperature and spent the same proportion of their day at very high body temperatures. However, the steeper temperature gradient available for passive cooling allowed those females to enhance maternal care by shortening their nest bout absences. In contrast, body temperatures of paired females were tightly regulated compared to the hyperthermia of solitary females and rarely included the highest body temperatures. This alleviation of maternal hyperthermia was not achieved through a reduction in nest attendance. Therefore, maternal hyperthermia in Djungarian hamsters is not essential and may be considered a substantial cost to females when males are not present.