David B. Croft

Field metabolic rate and water turnover of red kangaroos and sheep in an arid rangeland: an empirically derived dry-sheep-equivalent for kangaroos

Sustainable management of pastures requires detailed knowledge of total grazing pressure, but this information is critically lacking in Australia’s rangelands where livestock co-occur with large herbivorous marsupials. We present the first comparative measure of the field metabolic rate (an index of food requirement) of Australia’s largest marsupial, the red kangaroo (Macropus rufus), with that of domestic sheep (Ovis aries; merino breed). We tested the assumption that the grazing pressure of red kangaroos is equivalent to 0.7 sheep, and show this to be a two-fold overestimation of their contribution to total grazing. Moreover, kangaroos had extraordinarily lower rates of water turnover, being only 13% that of sheep. Consequently, our data support arguments that the removal of kangaroos may not markedly improve rangeland capacity for domestic stock. Furthermore, given the low resource requirements of kangaroos, their use in consumptive and non-consumptive enterprises can provide additional benefits for Australia’s rangelands than may occur under traditional rangeland practices.

Predator scent induces differing responses in two sympatric macropodids

When prey species encounter the scent of a predator they must make a decision on how to respond. This may be either to ignore, flee, hide or alarm call. While many species are able to derive detailed information from the chemical cues associated with predator scent, for some the decision to respond is often made without being able to identify the actual location and intentions of the predator. Depending on the sociality and ecology of the species, it may pay to flee or to engage in predator inspection where knowledge is impure. We tested for this in two sympatric marsupial macropodids, the parma wallaby (Macropus parma) and the red-necked pademelon (Thylogale thetis), as little is known of how these species detect and respond to olfactory cues of predation risk. We observed that, when presented with a synthetic predator scent mimicking dog urine, the social forager, T. thetis, tended to spend more time close to the predator odour, while the solitary forager, M. parma, exhibited an aversive response. The results suggest that social and ecological constraints on the sensory modalities used in predator detection may influence how macropodids respond to olfactory predator cues.

Playfighting in Captive Red-Necked Wallabies, Macropus Rufogriseus Banksianus

The structure and development of playfighting in captive red-necked wallabies, Macropus rufogriseus banksianus, was studied over a 2.5 year period. An ethogram of 21 acts was established. Playfighting involved acts from agonistic, affiliative and sexual contexts. The sequential organisation of acts was highly non-random in both intra- and inter-individual structure. Sequence analysis grouped acts into 3 subsystems : those associated with high (central act: Spar) and low (central act: Paw) intensity bouts of fighting; and those associated with initiation, termination or interbout behaviour. Wallabies playfought at varying intensities ranging from high intensity Sparring matches to low intensity bouts of Pawing coupled with frequent and prolonged periods of affiliative interactions. A third type of playfighting, refusal playfights, was of short duration and was probably failed playfight initiations. There was considerable repetition of acts and sequences of acts, and play-partners interacted in a highly mutual manner. Some acts (Skip, side and chest Autogroom, and Shake) were performed in an apparently exaggerated manner and may have had a communicative function. There was noticable restraint used in the performance of Kicking during playfights compared to that seen in serious fights. The goal of playfighting was either to gain unrestricted grooming access to an opponents throat or to force an opponent off-balance causing it to retreat. Males of any age playfought more often than females; playfighting in females was very rare. Wallabies engaged in playfights soon after they first began to leave their mothers pouch. Three phases of playfight development in males were identified. The first was an early phase of vigorous play that ended about the time wallabies were weaned. The second phase commenced after weaning and continued until after sexual maturity. It was a transitional period of increasing instability in playfight relations manifested as shorter playfights and more refusal playfights. The final phase was characterised by low intensity playfighting and was typical of older adult males. The design of playfighting and age/sex differences in its performance were used to consider the relative importance of motor training, socialisation and assessment of fighting skills as benefits of playfighting. Most evidence favours motor training as the most important benefit, particularly for high intensity playfighting. For low intensity playfights motor training was not completely satisfactory as the main benefit. It was possible that low intensity playfights gave a different type of motor training than high intensity playfights. Developmental changes in the type of playfighting performed also suggest that either the motor training benefits a wallaby required from play changes with age, or there were age-related changes in the function of playfighting. Neither socialisation or assessment of fighting skills seem to be major benefits of playfighting in the wallabies. The similarities between playfighting in the wallabies and play in better studied taxa (i.e. eutherians), and between wallaby playfighting and the descriptions given in the macropodid literature of prolonged, resource-unrelated serious fights are considered. It was concluded that at least some of the fights of macropodids reported in the literature were misclassed playfights.

Survival behaviour of swamp wallabies during prescribed burning and wildfire

Context.Prescribed(orcontrolled)burningisfrequentlyadvocatedasameansofreducingfuelloadsinperi-urbanforests to minimise the risk of high-intensity wildfires. An important consideration in prescribed burns is the impact on native wildlife. Aims. An opportunity arose to follow the movements of radio-collared peri-urban swamp wallabies during a prescribed burn and after an unexpected wildfire in the same location a short time later. Movement data was used to assess the relative impactsoftheprescribedburnandwildfireonmortality,emigrationandhabitatuse;thebehaviouralresponsesandmethods of avoidance used by swamp wallabies in response to an oncoming fire front; and the management implications for wildlife that inhabit fire-prone habitats in proximity to human settlement where wildfire mitigation is necessary. Methods. Here we report on the movements of radio-collared swamp wallabies, Wallabia bicolor, before, during and after a prescribed fire and after a wildfire on the same site 6 months later. Key results. No radio-collared swamp wallabies were killed during the prescribed burn and only one wallaby was observedtoemigratefromtheareapost-fire.Thiscontrastedtothewildfirewhereonewallabydiedduringorjustafterthe fire and another perished in the post-fire environment a few months later. The wildfire also increased emigration post-fire. Conclusions. We demonstrate that wallabies can avoid fire fronts and that this avoidance behaviour may be more successful during cooler fires. The prescribed burn provided a suitable habitat for wallabies but did not result in a shift in habitat preference. Implications. Mitigation of the impact of prescribed burns on swamp wallabies may be achieved by allowing sufficient time for habitat complexity to re-establish between burns.

Domestic pigeons (Columba livia) discriminate between photographs of individual pigeons

In two experiments, we examined the discrimination of photographs of individual pigeons by pigeons, using go/no-go discrimination procedures. In Experiments 1A and 1B, the pigeons were trained to discriminate 4 photographs of one pigeon from those of a number of pigeons. The subjects learned the discrimination, but their discriminative behavior did not transfer to new photographs taken from novel perspectives. When the pigeons were trained to discriminate between 20 photographs of five pigeons taken from four perspectives as the S+ and 20 photographs of five different pigeons as the S−, the subjects learned the discrimination, and this discriminative behavior partially transferred to new photographs taken from novel perspectives (Experiments 2A–2C). The results suggest that pigeons are able to discriminate among conspecific individuals, using stationary visual cues. This strengthens the assumption in evolutionary theory that animals can discriminate among individuals and encourages further investigation as to how this ability is used in various behaviors of animals.

Play behaviour and its effects on social development of common chimpanzees (Pan troglodytes)

The aim of the study was to monitor the social development of infant and juvenile common chimpanzees (Pan troglodytes) through their play behaviour at Taronga Zoo in Sydney in order to examine the possible effects of captivity (such as limited opportunities to play) on social development. Play behaviour was observed by focal animal sampling to determine individual differences, and their relationship to age, sex, and relatedness of the subjects. Analysis revealed marked individual variations in social, solitary, and object play behaviours indicative of a relatively well-balanced social and physical environment. Subjects showed a marked preference for play-partners of a different age compared to their own, and initiated interactions with similar frequency with members of both sexes. Many social-play dyads consisted of related individuals, and familiarity with prospective play-mates was the most decisive factor in social interactions.

Behavioural mechanisms of competition in small dasyurid marsupials

The competitive behaviour of three species of small dasyurid marsupial, Antechinus swainsonii, Antechinus stuartii and Sminthopsis murina, was assessed in specially designed enclosures and smaller encounter cages, by videotaping the activity of pairs of animals, both as conspecifics and members of different species (except for A. swainsoni versus S. murina). Spatio-temporal analyses revealed differences in activity patterns and interactions within and between the species. Interference competition occurred in all intraspecific and interspecific comparisons tested. Encounter competition was judged to be the mechanism operating as all animals entered into interactions with other individuals. Encounters were particularly prevalent within Antechinus, indicating that they were more social than the relatively solitary Sminthopsis. Avoidance behaviour occurred between the two Antechinus species and this may enable them to coexist, so that this mechanism may be considered to be avoidance competition. The smaller competitor, S. murina, showed avoidance of the larger A. stuartii. Intraspecific competition was judged to be stronger than interspecific competition, but the latter could have more severe consequences, with the death of the smaller species occurring in some situations. This highlighted the asymmetric nature of competition, with body size determining the outcome of interactions between species.

Educational and Conservation Value of Whale Watching

Many people support whale watching on the basis that it enhances people’s appreciation and awareness of the whales they are viewing and can lead to the protection of the species and of the environment generally. Because whale watching can directly impact on whales’ behavior it is important that whale watching is beneficial for people’s understanding of whales and for the conservation of whales. This article examines the educational and conservation value of the whale-watching experiences currently offered in New South Wales, Australia. The current education provided lacks structure, there are no clear conservation objectives, and there is limited addition to knowledge and conservation behaviors of whale watchers in the long term. Through improvement of the education provided during whale-watching experiences, it is argued that the whale-watching industry can become a more sustainable form of wildlife tourism and provide conservation benefits for whales and other forms of biodiversity.

Do wildlife warning reflectors elicit aversion in captive macropods

A goal to reduce the frequency of animal-vehicle collisions is motivating extensive research on this topic world-wide. Over the last 30 years, one popular mechanism to warn wildlife of approaching vehicles has been the wildlife warning reflector, manufactured and distributed under the brands Swareflex (Austria) and Strieter-Lite (USA). These reflectors were designed to scare deer and other ungulates from roadways at night by reflecting light from the headlights of approaching vehicles into the eyes of animals on the road verge. Robust documentation of their effectiveness has been lacking, yet there has been a push in Australia to examine their efficacy with regard to medium to large macropodids. Field trials of the reflectors are problematic and difficult to design rigorously, so we chose to examine the behavioural response of two captive macropodid species (Macropus rufus and M. rufogriseus) to the reflectors on a simulated road in order to derive some indication as to their efficacy. The behavioural response to the reflectors was negligible for both species and not consistent with an aversive effect to deter road use or crossing. We conclude that they would be of little value in our efforts to reduce the frequency of collisions of kangaroos or wallabies with vehicles in Australia.

The welfare ethics of the commercial killing of free-ranging kangaroos: An evaluation of the benefits and costs of the industry

The commercial killing of kangaroos provides multiple benefits to society, but also causes both deliberate and unintended harms to kangaroos. The ethics of the kangaroo industry is assessed in terms of whether the assumed benefits justify the welfare costs. An analysis of the stated benefits indicates that killing for damage mitigation is beneficial mainly during drought and not at current levels; that there is a commercial value, although considerably lower than previously estimated, and that demonstrable environmental benefits from commercial killing of kangaroos are lacking; and that the commercial kill may ameliorate the suffering of kangaroos during drought. Welfare practices are very difficult to assess and regulate due to the size and remote nature of the industry. A combination of empirical data on welfare outcomes and inferences drawn from behavioural and reproductive knowledge of the commercially killed species are utilised to assess harm. The welfare costs include deliberate and indirect harm to dependent young (a by-product of the commercial kill), and a number of unintended harms to adult kangaroos, including increased mortality during drought, inhumane killing of a portion of adult kangaroos, and a disruption of social stability and the evolutionary potential of individuals. Furthermore, a substantial gap exists between the intended welfare standards of the code of practice governing the kangaroo industry and the welfare outcomes for both dependent young and adult kangaroos. We found that, on balance, the benefits are lower than expected and the welfare costs are likely to be considerably higher than acceptable. More research, particularly at the point of kill, is necessary to verify and assess the extent of harms. A number of improvements are suggested to the code of practice to improve welfare outcomes.