Improving the success of captive breeding and reintroduction programs for
endangered species through mate choice

A project undertaken at Zoos Victoria and supervised by Michael Magrath

Captive breeding for reintroduction is a key component of the recovery strategy for many endangered species. For most of these programs, the goal is to return individuals to the wild, either to re-establish populations or supplement existing populations that are vulnerable to extinction. A common problem encountered in these breeding programs is an inter-generational decline in the quality of animals, resulting from issues such as inbreeding depression and the loss of genes important for success in the wild. To stem this decline, most breeding programs carefully manage pairings between individuals to help maximise the retention of genetic variability in the population. However, this approach to pairing usually prevents females from exercising any choice of mating partner which is likely to affect reproductive outcomes. There is growing evidence that mate choice promotes improved behavioural and/or genetic compatibility between mates, resulting in greater numbers and quality of offspring. Despite this, the potentially very significant benefits of mate choice have rarely been evaluated within breeding programs for endangered species.
This collaborative project between Zoos Victoria and the University of Melbourne addressed this question by determining whether mate choice is an effective tool to increase the success of breeding in captivity, using the critically endangered eastern barred bandicoot as a model system. Zoos Victoria houses a sizeable breeding population of this mid-sized marsupial, allowing the consequences of mate choice to be examined experimentally. More specifically, we determine whether:

  1. Females show consistent preference for particular males when presented with several potential mates.
  2. Females paired with ‘preferred’ males (as compared with ‘non-preferred’ males) are more likely to produce offspring and/or produce them sooner.
  3. Young produced from 'preferred' matings attain better condition compared to those from 'non-preferred' matings.

We estimated female preferences by measuring the time they spent interacting with each of two males, and by assessing behavioural signs of female receptivity. Females were then paired with either their ‘preferred’ or ‘non-preferred’ male, and the time to conception and number of pouch young produced recorded. Based on average interaction time during choice trials, females paired with ‘preferred’ males were significantly more likely to produce young (82% vs 33%).  These preferred pairings also resulted in earlier conception of young than non-preferred pairings (13d vs 49d). There was no difference in litter size or condition of young at weaning. Practical ways to integrate mate choice protocols into the eastern barred bandicoot breeding program are being considered. We hope that these findings will also encourage incorporation of mate choice into conservation breeding programs for other species.


 

Figure 1a. Diagram of experimental set-up showing relative positioning of male and female bandicoots


Figure 1b. Image showing the position of the encounter screen within a male enclosure, and open access doorway from the female enclosure in the back corner of the shared wall