Graeme Coulson

Diets of native and introduced mammalian herbivores in shrub-encroached grassy woodland, south-eastern Australia.

Effective management of sympatric mammalian herbivore populations requires an understanding of interspecific interactions. At Wilsons Promontory National Park, Victoria, sympatric native and introduced mammalian herbivores are thought to be contributing to modification of shrub-encroached Coastal Grassy Woodland. We estimated the diets of the five terrestrial mammalian herbivore species present using microhistological techniques. The diets of introduced hog deer (Axis porcinus) and native swamp wallabies (Wallabia bicolor) consisted mainly of dicots. The diet of introduced European rabbits (Oryctolagus cuniculus) contained similar proportions of monocots and dicots. The diets of native eastern grey kangaroos (Macropus giganteus) and native common wombats (Vombatus ursinus) consisted mainly of monocots but kangaroos also consumed moderate amounts of dicots. Deer and wallabies consumed more native plants than did the other species and rabbits consumed more exotic plants than did all other species except kangaroos. Diet breadth was narrowest for kangaroos and broadest for swamp wallabies and hog deer. Overlap in food use by the five herbivores was high, particularly between deer and wallabies, and between kangaroos and both rabbits and wombats. Our results suggest that the potential impacts of native and introduced species on the vegetation of Coastal Grassy Woodland are similar, and that the entire herbivore assemblage will need to be managed to increase fine fuel loads if fire is used as a restoration tool.

Experimental manipulation of fertility reveals potential lactation costs in a free-ranging marsupial

Lactation is the most energetically expensive component of reproduction in mammals. Theory predicts that reproducing females will adjust their behaviour to compensate for increased nutritional demands. However, experimental tests are required, since comparisons of the behaviour of naturally reproducing and non-reproducing females cannot distinguish between true costs of reproduction, individual differences or seasonal variation. We experimentally manipulated reproduction in free-ranging, eastern grey kangaroos (Macropus giganteus), using a fertility control agent. Our novel field experiment revealed that females altered their behaviour in direct response to the energetic demands of reproduction: reproducing females increased bite rates, and thus food intake, when the energetic demands of lactation were highest. Reproducing females did not reduce the time spent on vigilance for predators, but increased their forage intake on faecal-contaminated pasture, thereby increasing the risk of infection by gastrointestinal parasites—a largely unrecognized potential cost of reproduction.

Fertility control in the eastern grey kangaroo using levonorgestrel implants

We investigated the effect of subcutaneous levonorgestrel implants on reproduction, gestation, lactation, and body condition in both captive and free-ranging populations of female eastern grey kangaroos (Macropus giganteus). Kangaroos had their pouch young removed and were given either 2 control (inert) or 2 levonorgestrel implants. During January 1999, 3 kangaroos in the captive population received control and 3 received levonorgestrel implants. All of the control-treated females had given birth 3 months after treatment. None of the levonorgestrel-treated females gave birth during the investigation (25 months). In the free-ranging population, 8 females received control and 18 received levonorgestrel implants. Seven of the controls and 3 of the levonorgestrel-treated females gave birth during the first year. The 3 levonorgestrel-treated females that reproduced confirmed that levonorgestrel does not affect the reactivation or subsequent development of a blastocyst in diapause and that it has no effect on parturition. All 3 pouch young were successfully reared to weaning, demonstrating that levonorgestrel treatment does not affect the establishment or maintenance of lactation. All of the control-treated females gave birth to new young during the second year, whereas none of the levonorgestrel-treated females reproduced. Mean body weight of the levonorgestrel-treated females increased by 13.8%, significantly more than the 1.2% increase in control-treated females. However, a comparison of leg and foot length versus weight change identified 4 young females in the levonorgestrel-treatment group that underwent considerable somatic growth during the investigation. When these females were removed from the treatment group, no significant difference occurred between the 2 groups. Therefore, levonorgestrel had no adverse effect on body condition in the kangaroos. Levonorgestrel implants provide a safe, highly effective, and long-term (at least 27 months) method of contraception for eastern grey kangaroos. We confirm that this contraceptive system has potential for managing overabundant captive and selected wild populations of macropodid marsupials.

A capture technique for free-ranging eastern grey kangaroos (Macropus giganteus) habituated to humans

Available methods to capture free-ranging kangaroos differ in ease of use, selectivity, risk of injury and suitability to specific environments. We describe a simple technique involving the syringe from a ‘jabstick’ attached to an extendable, aluminium pole. We also examine responses of eastern grey kangaroos (Macropus giganteus) to a range of doses of Zoletil®. We captured 307 eastern grey kangaroos that were habituated to humans in Victoria, Australia, from November 2007 to October 2009. We approached kangaroos on foot, and injected the hind limb muscle mass with the pole syringe extended up to 4.85 m. We used Zoletil® 100 at a dose rate of 4.1 ± 1.3 mg kg–1 (mean ± s.d., n = 274). Induction was rapid (4.3 ± 2.0 min, n = 185) and only weakly related to dose (r2 = 0.06). There was no clear relationship between age, sex or body condition and induction time. This pole syringe technique can be successfully and safely used wherever animals can be approached closely, regardless of body condition. The technique provides an effective means to immobilise habituated kangaroos for research and management.

Monospecific and Heterospecific Grouping and Feeding Behavior in Grey Kangaroos and Red-Necked Wallabies

Benefits of grouping by conspecifics as an anti-predator strategy also should apply in heterospecific associations if species are similar in their vulnerability to predation. I investigated monospecific and heterospecific grouping by sibling species, eastern ( Macropus giganteus ) and western grey kangaroos ( M. fuliginosus ), together with smaller and less social red-necked wallabies ( M. rufogriseus ). I observed groups feeding in mornings and evenings on a grassy airfield in the Grampians National Park, western Victoria, Australia. Wallabies formed smaller monospecific groups than the kangaroos, maintained a greater nearest-neighbor distance, and moved more while feeding. Monospecific groups of the two kangaroo species were indistinguishable in size, composition, spacing, and feeding rates. The percentage of individual grey kangaroos feeding increased with group size in monospecific groups of up to six. Heterospecific groups of kangaroos formed frequently, and the percentage of individual eastern and western greys feeding was not affected by species composition of groups, suggesting that conspecifics and heterospecifics were equally valuable as feeding partners. By contrast, there were few associations between kangaroos and wallabies.

Habitat selection by adult female eastern grey kangaroos

We determined patterns of habitat selection in the winter–spring period by adult female eastern grey kangaroos (Macropus giganteus) at Yan Yean Reservoir Catchment near Melbourne, Victoria, during 1994–95. We assessed habitat selection at two levels by radio-tracking 11 adult female kangaroos. The 95% isopleth harmonic mean home-range size (mean = 62.3 ha) was the smallest recorded for female eastern grey kangaroos. No range encompassed all of the habitat types available in the study area, and the mix and rankings of habitats selected at this level varied amongst individuals when compared by compositional analysis with available habitats. Selection of habitats at the within-range level also varied among individuals and differed between night and day for many individuals, but not for the population mean. Individuals selected strongly for good foraging habitat within their ranges. In particular, grassy clearings were used by all individuals and were selected strongly by day, night or at both times.

Citizen science: recruiting residents for studies of tagged urban wildlife

The human residents of cities represent a largely untapped and potentially vast source of information about urban wildlife. One simple and scientifically valuable contribution involves the reporting of sightings of tagged animals, but even in urban areas, such reports are relatively rare. We draw on two case studies of conspicuously tagged and iconic animals to consider human reactions to wildlife tags, and how these influence the likelihood of unsolicited reports. We evaluate potential strategies for increasing participation from this pool of potential citizen scientists and maximising the reliability of these contributions. In both studies, public reports contributed substantial and largely accurate data. We conclude that such reports are often of unique value, and that common sources of reporting error can be minimised by careful tag design and clear advice to participants. Effective information campaigns can have unexpected effects on reporting rates, but in general, communication is crucial to raising awareness and encouraging public involvement. New interactive web-based tools have the potential to dramatically increase public accessibility to information and encourage involvement by providing instant feedback, access to research updates, and encouraging the formation of clusters of citizen scientists.

Long-term pair-bonds without mating fidelity in a mammal

Most mammals are polygynous and are characterised by male-biased sexual size dimorphism. One hallmark of mammalian monogamy is the lack of such dimorphism. Bobucks, or mountain brushtail possums, Trichosurus cunninghami, lack sexual size dimorphism; however, few behavioural data exist for this species. We studied the mating system of a bobuck population in south-eastern Australia. Adult bobucks were strongly paired: pair-members had exclusive access to a suite of den-trees and overlapped in home range on average by 70%. Pair-members rested together in the same tree-hollow on approximately 70% of days during the breeding season and 47% of days during the non-breeding season. While active, pair-members remained within approximately 8 m of one another during the breeding season and within 31 m of one another during the non-breeding season. Females established pair-bonds at 2-5 years of age; pair-bonds ended only as a result of the death of one pair member. However, molecular paternity analysis established that 35% of young were the result of extra-pair copulations (EPCs). This is the first study to provide strong evidence of long-term pair-bonds in a marsupial and raises questions about the relative benefits of pairing to males and females in this population.

Fertility Control of Eastern Grey Kangaroos: Do Levonorgestrel Implants Affect Behavior?

Wild populations of eastern grey kangaroos (Macropus giganteus) can pose serious management problems when conditions favor a high population growth rate. Contraception methods are becoming an ethically more acceptable alternative to culling or translocation when dealing with population control of large mammals. We investigated behavioral effects of levonorgestrel contraception in this species. A total of 82.4% of female eastern grey kangaroos treated with levonorgestrel implants did not reproduce, whereas only 12.5% of control females did not reproduce. Levonorgestrel contraception had no significant effect on time spent feeding, scanning, grooming, moving, and sexual interactions with males during the observation sessions. However, control females spent more time in open paddocks feeding than contracepted females over a 24-hr period. Males preferred to associate with groups containing more (and a higher percentage of) control females.

Deslorelin implants in free-ranging female eastern grey kangaroos (Macropus giganteus): mechanism of action and contraceptive efficacy

Abstract Context. Fertility control offers a non-lethal management technique for iconic yet overabundant wildlife. Slow-release hormonal implants containing deslorelin show promise for managing free-ranging populations, particularly in peri-urban reserves, but most studies have been limited to captivity. Aims.. We investigated the efficacy and mechanism of deslorelin implants in free-ranging female eastern grey kangaroos (Macropus giganteus) under realistic management conditions. Methods. We assigned females to a deslorelin (9.4 mg, n = 53) or placebo (n = 56) group at three peri-urban sites in Victoria, Australia, and monitored reproductive success for 3 years by observing young in the pouch. We tested the plasma LH response of control and treated females to exogenous GnRH, and compared the size of ovarian follicles between the two groups. Key results. Deslorelin implants reduced fertility at all three sites. No deslorelin-treated females bred in Year 1 at Anglesea and Serendip versus 42% and 44% of control females respectively. At Plenty Gorge, 60% of deslorelin-treated females bred in Year 1 versus 100% of control females. In Year 2, between 11% and 39% of the treated females bred versus between 82% and 100% of control females at all sites. The contraceptive efficacy reduced by Year 3 when between 43% and 57% of the treated females bred versus between 85% and 100% of controls. A GnRH challenge elicited higher plasma LH concentrations in control than in treated females, and unlike untreated females, treated females lacked ovarian follicles >2 mm. Conclusions. Deslorelin implants reduced fertility in free-ranging female eastern grey kangaroos over three successive breeding seasons. Chronic exposure to deslorelin desensitised the pituitary gland to GnRH and suppressed follicular development, but did not inhibit the development of a blastocyst, pregnancy or lactation in at least some females that had conceived before treatment. Implications. Effective population management using deslorelin implants will require females to be re-treated on multiple occasions because the contraceptive effect lasts only a portion of their reproductive life. This would be practical only at sites where kangaroos are relatively easy to capture. The timing of treatment is also important in a species that undergoes embryonic diapause, particularly at sites providing high-quality habitat.