Investigations into the health of brush-tailed rock-wallabies (Petrogale penicillata) before and after reintroduction

Abstract

The health of reintroduced animals has received little attention despite the potential impacts of poor animal health on the overall success of the reintroduction and potential risks to the host environment. As part of a reintroduction program, captive-bred brush-tailed rock-wallabies (BTRWs) (Petrogale penicillata) were hardened-off for at least three months before release into the Grampians National Park, western Victoria. A total of 41 animals were involved in the project, with the 24 selected for hardening-off aged between 1.1 and 4.3 years. In all, 21 animals have been released, with data from 11 collected from all sites (captive, hardening-off and reintroduced). At each site animals were periodically trapped, anaesthetised, physically examined, weighed, and blood sampled for haematological and biochemical data over three calendar years. All reintroduced animals were radio-collared. This study presents data across sites (167 samples), two seasons (winter/spring, 95 samples; summer/autumn, 72 samples), two different age groups (juveniles <1.25 years and subadults/adults >1.25 years) and both sexes. Seventy percent of released BTRWs and90% of sympatric macropodids were positive for macropod herpes virus; none of three BTRWs tested for toxoplasmosis was positive. Faeces were collected opportunistically for flotation and ectoparasites were collected and identified. While physical examinations with anaesthesia were safe and eliminated some animals from being released, they failed to detect all cases of oral cavity disease. A reference range of haematological and biochemical parameters have been established for this evolutionarily significant unit of BTRW. Lymphocyte/neutrophil ratios of released animals suggested that the main acute stressor is a handling phenomenon but the oxidative stress index suggested that animals were coping with their environment. Significant site differences were noted for several variables including red cell mass (red cell count, haemoglobin, haematocrit), white cell count, lymphocyte/neutrophil ratio, albumin globulin ratio, creatinine, urate, ascorbic acid, a-tocopherol, retinol, cholinesterase, total carotenoids and oxidative stress index. Significant seasonal differences were noted for some variables, including red cell mass, ascorbic acid, albumin globulin ratio, cholinesterase, total carotenoids and retinol. Significant age differences were noted for red cell mass, albumin and dietary antioxidants. The only sex-related difference related to higher retinol levels in females. Those parameters related to diet, e.g. albumin, retinol, a-tocopherol, ascorbic acid, and total carotenoids were consistent with those found in other rock-wallabies.