Physiological changes in the brushtail possum (Trichosurus vulpecula) following relocation from Armidale to Brisbane, Australia

To determine the effect of relocation on the health of possums the body wei ghts and hormone and immune responses of six male and nine female brushtail possums were monitored for 20 weeks following transfer from the environs o f Armidale into enclosures in Brisbane. Over the first 6 weeks of captivity , male possums lost 11.0% of their original body weight and females lost 16 .8%. The mean concentrations of plasma cortisol in the male and female poss ums were 14.5 and 29.4 ng/mL, respectively, and did not change over the 20- week period. Male and female possums displayed a similar pattern of thyroxi ne secretion over the 20 weeks, with low concentrations up to week seven (2 .1 and 2.7 ng/mL, respectively) increasing to 6.9 and 5.8 ng/mL in weeks 7- 12 (P < 0.005). This increase in the concentration of thyroxine corresponde d with the increase in body weight. The number of white blood cells (WBCs) and the percentage of neutrophils increased from the capture to week 6-10. However, during the last 10 weeks of captivity the number of WBCs and the p ercentage of neutrophils decreased, indicating recovery of the immune syste m. This was in accord with the proliferative response of lymphocytes to the T cell mitogen PHA that increased from weeks 11-15 to weeks 16-20 in both male and female possums. The results above suggest that the Armidale possum s, like the Brisbane possums, were stressed following their relocation; how ever, their immune systems were able to gradually recover as they adjusted to their new environment in Brisbane. The death rate of pouch young and of adult female possums after relocation was considerably higher in the Armida le possums compared to Brisbane possums. The mortality rate of Brisbane pos sums over the first 20 weeks of captivity was 8.3% and 19.6% for male and f emale possums, respectively, and for Armidale possums 16.6% and 47.1%, resp ectively. The possums transferred from the environs of Armidale into captiv ity in Brisbane were under greater stress than possums captured in Brisbane and placed in captivity in Brisbane. J. Exp. Zool. 284:42-49, 1999. (C) 19 99 Wiley-Liss, Inc.