Identifying the reproductive state of female Julia Creek dunnarts (Sminthopsis douglasi) by behavioural observations

Abstract

[Abstract]: The Julia Creek dunnart (Sminthopsis douglasi) is an endangered carnivorous marsupial. A recovery plan for the species has been initiated by Queensland Parks and Wildlife Service, which includes captive breeding. An important factor in breeding S. douglasi is the identification of oestrus. The current method to identify oestrus consists of examining urine samples for presence of cornified cells. To collect urine, the animals have to be removed from their cages and restrained. This method is stressful for the animals, as well as time consuming. The aim of this study was to identify specific behaviour of S. douglasi associated with oestrus, which could be readily observed without the need for handling the animal. This would provide a non-invasive way of identifying oestrus, which would facilitate breeding the species in captivity and planning conservation programs. Behaviour of S. douglasi was observed throughout the night by video recording. The most striking result was the increase in activity of the female when she was in oestrus compared to non-oestrus. The most informative behaviour to observe was entry by the female into the nest box and the frequency with which she entered the area closest to the wall of the enclosure. A discriminant function analysis generated an equation with an over-all predictive power (OPP, the probability of making an accurate identification of reproductive state) of 89%. This result was obtained by watching two random five-minute periods of activity. The equation was tested and verified with new individuals and attained a similar level of OPP. However, the equation was less accurate when the observed female’s social context was changed from being housed adjacent to a male, to being accompanied by another female or housed singularly. Consistent with the sensitivity of activity levels as an indicator, the distance run in an exercise wheel was also a good predictor of oestrous state. Females ran a significantly longer distance in their exercise wheel when in oestrus compared to non-oestrus (p<0.001).