Resistance to the nitrogen-mobilizing, diabetogenic action of cortisol in a small wallaby (Setonix brachyurus)

Faecal corticosteroid levels as an indicator of well-being in the tammar wallaby, Macropus eugenii

Faecal corticosteroid levels were measured in five female tammar wallabies, Macropus eugenii, at Macquarie University, NSW, Australia, to assess their reliability as indicators of well-being in this species. Animals were challenged with a change in conditions over the course of approximately 1 week, comprising movement from group yards to isolation in individual yards, in order to impose a disturbance to homeostasis ("stress"). Faecal samples were collected in 24-h intervals during the study period and analysed for corticosteroid concentration. The use of enzyme immunoassay for the measurement of corticosteroids in marsupial faecal pellets was validated. We observed a significant increase in faecal corticosteroids upon isolation and movement. Faecal corticosteroids remained above initial levels in all five animals throughout the study period, suggesting that faecal corticosteroid concentrations may be a useful indicator of a change in animal well-being. Faecal corticosteroid levels did not correlate with serum cortisol levels, implying that the use of noninvasive methods in a representative marsupial, the tammar wallaby, has the potential to provide information that is not readily apparent using blood-based protocols. Faecal corticosteroid analysis therefore has the potential for application in monitoring the well-being of captive and managed marsupial populations, as part of an integrated system of measures of animal health and well-being.

Adaptation of wild-caught Tasmanian devils (Sarcophilus harrisii) to captivity: evidence from physical parameters and plasma cortisol concentrations

This study assessed whether capture and transferral into captivity represents a significant stressor to Tasmanian devils. Four male and four female devils were captured in the wild and housed for 6 months in captivity in male–female pairs. Blood samples were collected for cortisol assay at capture, every 24 h for the first 4 days, and then monthly; body weight and tail width were monitored weekly. In the males, mean plasma cortisol concentrations were highest (49 ± 9.19 ng mL–1) at the time of initial capture; cortisol concentrations declined significantly after 48 h in captivity (9.2 ± 5.96 ng mL–1) and did not change significantly over the months in captivity. Females exhibited a different pattern: plasma cortisol concentrations were highest (74.0 ± 3.24 ng mL–1) in the initial sample, but mean concentrations remained elevated in samples taken at 24, 48 and 96 h after initial capture, and did not exhibit a significant decline (to 20.65 ± 8.95 ng mL–1) until 4 weeks after capture. During the first 2 months in captivity, the male devils lost ~8.7% of their original body weight, and females lost 10.6% during this same period. However, body weights then rose during the rest of the experiment. These results suggest that Tasmanian devils experience elevated plasma cortisol concentrations in response to capture and transfer into captivity. However, these high concentrations are not maintained during 6 months in captivity, suggesting that the animals are not chronically stressed.

The effects of age, season, and gender on serum cortisol levels in the tammar wallaby, Macropus eugenii

Serum cortisol levels were measured in a total of 73 tammar wallabies maintained in a captive population at Macquarie University, NSW, Australia. Previous studies of corticosteroids in marsupials have generally involved low sample numbers, a diverse array of analytical techniques, and a variety of sampling conditions. We have conducted a substantive, longitudinal study of serum cortisol levels using a radioimmunoassay protocol, and data have been analysed with respect to age, sex, and seasonality. There were no apparent effects of age or sex on serum cortisol levels, although an inverse but non-significant relationship was observed between males and females. However a significant difference in serum cortisol levels was observed between seasons, with mean serum cortisol significantly higher in summer than in autumn. These data will serve as a reference for 'normal' ranges of serum cortisol levels, particularly in the female tammar wallaby. As deviations from these values can indicate compromised animal health and well-being, this information will assist wildlife managers in assessing and monitoring the health status of individuals in captive and free-ranging populations.