David Schultz

Cross-fostering, growth and reproductive studies in the brush-tailed rock-wallaby, Petrogale penicillata (Marsupialia : Macropodidae): efforts to accelerate breeding in a threatened marsupial species

Pouch-young removal and cross-fostering trials were undertaken in the brush-tailed rock-wallaby, Petrogale penicillata, to assess whether this procedure could be used to accelerate breeding and recruitment in this threatened marsupial species. Basic reproductive data, lacking at the time of the study, were also collected. Eighteen pouch young, weighing 1 - 106 g, were fostered to either tammar wallaby, Macropus eugenii, or yellow-footed rock-wallaby, Petrogale xanthopus, surrogate mothers. Sixteen P. penicillata pouch young were transferred to surrogate mothers whose own young were greater or equal in size to the P. penicillata young being transferred. Fourteen of these young survived ( 88%). Two of the P. penicillata pouch young were transferred to surrogate mothers whose own young was smaller in size than the P. penicillata young being transferred. Neither survived. Growth curves for pouch young on mothers and surrogate mothers were estimated. P. penicillata young reared by surrogate mothers grew at a similar rate, and were weaned at a similar age, to the pouch young of the foster species. Like other rock-wallaby species, P. penicillata underwent embryonic diapause and had a gestation period of similar to 30 days. Permanent pouch exit occurred at similar to 200 days and young became sexually mature at similar to 23 months for males and no later than 21 months for females. This study clearly demonstrates that pouch young of P. penicillata, as small as 1 g (similar to 8 days old), can be removed and cross-fostered successfully. These procedures can be used to accelerate breeding and recruitment by up to six times in this threatened species provided an adequate source of surrogate mothers is available.

Sarcoptic mange in southern hairy-nosed wombats (Lasiorhinus latifrons): distribution and prevalence in the Murraylands of South Australia

This study examined the history, prevalence and distribution of sarcoptic mange in southern hairy-nosed wombats (Lasiorhinus latifrons) in the Murraylands, South Australia. Results from a survey suggested that there had been a long history of sporadic mange outbreaks, with 43% of 85 respondents indicating that they had seen diseased animals. There was a concentration of positive sightings (59%) in the vicinity of one town, Swan Reach. A total of 67 wombats was also caught on three pastoral properties; 0% (n = 21), 4% (n = 21) and 76% (n = 23) were found to have mange at each respective site. Diseased wombats presented with erythema, parakeratosis and alopecia and had lower median condition, subcutaneous fat and higher bone prominence scores than healthy animals. Severely diseased adult wombats had an average bodyweight that was 9.86 kg lower than those without mange. Infected animals suffered higher mortality, with a rate of ~37% in eight months on one property. It is suggested that mange may have a significant effect on southern hairy-nosed wombats and outbreaks could result in the decline and/or possible extinction of small, isolated populations. Population management initiatives, including suspending culling quotas in infected populations, should thus be considered.

REVIEW OF SURROGACY PROGRAM FOR ENDANGERED VICTORIAN BRUSH-TAILED ROCK WALLABY (PETROGALE PENICILLATA) WITH SPECIAL REFERENCE TO ANIMAL HUSBANDRY AND VETERINARY CONSIDERATIONS

Abstract A surrogacy program to increase the reproductive rate of the critically endangered Victorian brush-tailed rock wallaby (Petrogale penicillata), initially developed in semicaptive conditions, was established in close captivity at Adelaide Zoological Gardens in 1998. Pouch young were removed from their mothers on days 8–20 or 40–45 after parturition and placed onto the teat of a tammar wallaby (Macropus eugenii) or yellow-footed rock wallaby (Petrogale xanthopus xanthopus) surrogate mother. During the early years of the program, mortality of brush-tail pouch young was high (12/16, 75%), both before transfer while still on their mother (5/16) and after transfer to a surrogate mother (7/11). Changing pouch young transfer methodology and improving the health status of the surrogate animals during the later years of the program significantly reduced the mortality of brush-tail pouch young (8/29). Under the new methodology, no mortality of brush-tail pouch young was observed between birth and the time of transfer, (0/29), and after transfer, pouch young mortality rate was eight of 29 (28%). Factors implicated in the improved success of the program included 1) the early transfer (between days 8 and 20) of brush-tail pouch young from mother to surrogate mother, 2) review of the veterinary history and health of the animals selected to act as surrogate mothers, and 3) increased access to grazing pasture for foster mothers. The reproductive rate of the brush-tail females in the later years of the breeding program was sixfold above natural birthing rates. These and other factors important in establishing a breeding program of this nature are discussed.

Ultrastructure and motility of spermatozoa in macropodid and potoroidid marsupials.

In order to gain some understanding of the significance of the morphological features of spermatozoa within the Macropodoidea, the motility of spermatozoa from two macropodids (Petrogale xanthopus and Dendrolagus matschiei) and the motility, number and distribution of spermatozoa from three potoroidids (Aepyprymnus rufescens, Bettongia penicillata and Potorous tridactylus) were examined. Sperm were collected by electro-ejaculation or from the cauda epididymides. Epididymides from the potoroidids were divided into 12 regions. One epididymidis per animal was fixed for light and transmission electron microscopy and, on the contralateral side, the number of sperm, their distribution and motility were determined. In general, spermatozoa of all five species differed markedly from one another in head and flagella dimensions. Spermatozoa from B. penicillata and P. tridactylus were significantly longer and broader and had a smaller acrosome relative to head length, and there was a radial displacement of dense fibres. They also progressed more rapidly in standard culture media. Spermatozoa from at least three species were able to alter their motility pattern in vitro as media viscosity increased. Sperm movement in all species appeared to be restricted to one plane and showed no evidence of rotation, whereas lateral head displacement was often pronounced; there was no evidence of a sinusoidal mode of progressive motility. Testicular and epididymal sperm numbers in A. rufescens and P. tridactylus were relatively high (approximately 17.5-50 x 10(6)). In A. rufescens, approximately 69% of all epididymal sperm were located in the cauda epididymidis compared with approximately 40% in P. tridactylus. This study demonstrated that marked radial displacement of the dense fibres is probably closely associated with the ability to develop a sinusoidal mode of progressive movement, and that this feature of the sperm tail structure is not just linked with sperm size. Sperm size, however, is associated with sperm velocity.

Detection and identification of a Gammaherpesvirus in Antechinus spp. in Australia

Abstract We detected herpesvirus infection in a male yellow-footed antechinus (Antechinus flavipes) and male agile antechinus (Antechinus agilis) during the period of postmating male antechinus immunosuppression and mortality. Histopathologic examination of tissues revealed lesions consistent with herpesvirus infection in the prostate of both animals. Herpesvirus virions were observed by transmission electron microscopy in the prostate tissue collected from the male yellow-footed antechinus. Herpesvirus DNA was detected in prostate, liver, lung, kidney, spleen, and ocular/nasal tissues using a pan-herpesvirus PCR targeting the viral DNA polymerase. Nucleotide sequencing identified a novel herpesvirus from the Gammaherpesvirinae subfamily that we have tentatively designated dasyurid herpesvirus 1 (DaHV-1).

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

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 both sexes. Seventy percent of released BTRWs and 90% 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, α-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, α-tocopherol, ascorbic acid, and total carotenoids were consistent with those found in other rock-wallabies.

PHARMACOKINETICS OF MOXIDECTIN IN THE SOUTHERN HAIRY-NOSED WOMBAT (LASIORHINUS LATIFRONS)

Sarcoptic mange, caused by Sarcoptes scabiei var. wombati, could be a significant threat to populations of southern hairy-nosed wombats (Lasiorhinus latifrons; SHNW) in Australia. Treatment is currently based on the off-label use of various parasiticidal drugs, with limited clinical efficacy trials. Our primary aim was to determine the pharmacokinetic parameters of a macrocyclic lactone, moxidectin, to assist in the development of effective treatment protocols. Pharmacokinetic parameters were determined in four female SHNW following a single subcutaneous injection of 0.2 mg/kg moxidectin. Blood samples were collected for 38 days following injection (August–September 2008), for analysis using liquid chromatography and tandem mass spectrometry. The mean peak plasma concentration occurred at 13.6 hr, with a mean peak plasma level of 98.6 ng/ml. The mean elimination half-life was 5.03 days, resulting in a mean area under the curve of 377 ng.day/ml. The peak plasma moxidectin concentration was higher than that seen in livestock species but the plasma elimination half-life was shorter. This study suggests that a single injection of 0.2 mg/kg moxidectin may not be sufficient to clear a mange infection in this species.

Effects and treatment of sarcoptic mange in southern hairy-nosed wombats (Lasiorhinus latifrons).

We examined the clinical and cellular effects of sarcoptic mange on southern hairy-nosed wombats (SHNW, Lasiorhinus latifrons) and the effectiveness of a single dose of ivermectin as a treatment for captive and wild animals. Wambats were caught at three sites in South Australia between April and August 2005 and blood and skin samples were collected. Hematology, biochemistry, and protein electrophoresis reference intervals were determined for healthy and diseased SHNW. Diseased SHNW had significantly higher white blood cell counts, neutrophils, lymphocytes, and total protein but lower red blood cell counts, hemoglobin, hematocrit, and creatinine. Microscopic investigation indicated substantial hyperplasia, hyperkeratosis, and fluid infiltration into the dermis and epidermis of diseased animals. Conclusions on the efficacy of a single dose of ivermectin were limited by low sample size (n=5, two captive and three wild SHNW) and are preliminary. However, ivermectin effectively treated mild, but not severe, mange in wild SHNW and severe mange in captive animals. This study has implications for the conservation and management of SHNW and the broader Vombatidae family.

Reintroduction methods and a review of mortality in the brush-tailed rock-wallaby, Grampians National Park, Australia

Abstract. Captive-bred brush-tailed rock-wallabies (BTRW) were reintroduced into the Grampians National Park, Australia, during 2008–12. Two release strategies (methods) were examined: ‘Small release with supplementation’ (Strategy 1) and ‘Larger release, no supplementation’ (Strategy 2). Of the 39 animals released, 18% survived. Thirty-six percent of all mortality occurred within the first 100 days. Under Strategy 1, 22 animals were released in five groups. Twenty deaths occurred across 48 months, with predation estimated to account for 15% of mortalities. Under Strategy 2, 17 individuals were reintroduced across one month. Twelve deaths occurred in the five months following release, with predation estimated to account for 83.4% of mortalities. Of the independent variables tested for their relationship to survival time after release, release strategy was the only significant predictor of survival time after release with the risk of death 3.2 times greater in Strategy 2. Independent variables tested for their relationship to predation risk indicated that release strategy was also the only significant predictor of predation risk, with the risk of death associated with predation 10.5 times greater in Strategy 2. Data suggested that fox predation was the main factor affecting BTRW establishment. Predation risk declined by 75% during the first six months after release. A significant positive relationship was also found between predation risk and colony supplementation events. We conclude that predation risk at Moora Moora Creek is reduced in releases of fewer animals, that it declines across time and that disturbing BTRW colonies through the introduction of new animals can increase predation risk. We recommend that future reintroductions should employ diverse exotic predator control measures at the landscape scale, time releases to periods of lowest predator activity, and limit colony disturbance to maintain group cohesion and social structure. Furthermore, the preferred method of population establishment should be single, small releases over multiple sites without supplementation. Further testing of the reintroduction biology of this species is urgently required.