151 Seasonal Reproduction in Wild and Captive Male Koala Populations in South-East Queensland

Abstract

Seasonal changes in male reproductive function were assessed in a wild free-range population (n = 10; obtained every six weeks from January to November 2005), a deceased wild free-range population (n = 84; obtained monthly from September to August 2005) and a captive population (n = 7; obtained monthly from October 2005 to October 2006) of koalas in south-east Queensland. This study also determined the practicality of using free-range wild male koalas as potential semen donors for genome resource banks. Examination of a range of reproductive variables initially revealed no significant seasonal change in the 3 koala populations; however, when the data were adjusted to account for individual koalas, their size and/or their health status, the majority of reproductive parameters showed evidence of seasonal variation that was supported by statistical modeling. Relationships between variables were based on simple polynomials, up to a cubic for some variables. Total testicular volume changed throughout the year in the wild and captive populations with an increase over spring and summer and a decrease in autumn and winter; no such change was detected in the deceased population. Maximum area of the sternal gland stain occurred in spring in both the deceased and captive populations but in winter for the wild free-range population. Total bulbo-urethral gland volume in the deceased population showed an increase over spring, a decrease over summer and autumn and then an increase towards the end of winter. The steroidogenic capacity of the koala testis (testosterone secretion) in both the wild free-range (live) and captive populations showed a peak during spring and a nadir in autumn. The quality of semen samples collected by electroejaculation from the wild (live) and captive koala populations showed evidence of being influenced by season. Initial percentage motility of the wild population decreased marginally throughout the study and initial rate of sperm movement was highest in winter. Motility of spermatozoa after thawing from the wild koala population was also highest in winter as was the percentage of cryopreserved spermatozoa with intact plasma membranes collected from the captive population. This study has shown that male koala reproduction in south-east Queensland is seasonal and that it is possible to repeatedly collect semen from free-range koalas as potential genetic donors. Nevertheless, semen quality from captive and wild caught animals appears to be susceptible to seasonal change and winter appears to be the optimal season in which to collect such samples. We are grateful to the veterinary staff, zookeepers, and volunteers at Dreamworld for their assistance with general animal husbandry. We also sincerely thank the many veterinarians, volunteers, and Queensland Parks and Wildlife Service staff that assisted with this project whose help was invaluable for the accomplishment of this project. This project was funded by an Australian Research Council (ARC) Grant, the School of Animal Studies (SAS) The University of Queensland, and the Queensland Government’s Koala Enhanced Genetic Exchange Program (KEGEP).