Social Behavior and Organization in the Macropodoidea

Occurrence patterns of sympatric forest wallabies: assessing the influence of structural habitat attributes on the coexistence of Thylogale thetis and T. stigmatica

Background

We studied the occurrence of two sympatric wallabies, the red-necked pademelon (Thylogale thetis) and the red-legged pademelon (T. stigmatica) in northeastern New South Wales, Australia in relation to structural habitat attributes. At our study site, both species inhabit closed forest environments and have overlapping distributions, but T. thetis leaves the forest at night to graze adjacent grassy forest edges whereas T. stigmatica remains within the forest and browses forest vegetation. The objectives of the study were to investigate how structural attributes of two forest types, wet sclerophyll forest and rainforest, relate to the fine-scale occurrence of these two wallaby species within the forested environment.

Methods

We gathered occurrence data from 48 camera trap stations divided equally between rainforest and wet sclerophyll forest. At each camera point, we also measured a range of structural habitat attributes to determine habitat affiliations for the two Thylogale species. Principal component analyses were used to describe major trends in habitat, and generalised linear models were used to describe the efficacy of the variables in predicting habitat occurrence of each species.

Results

The number of occurrences of Thylogale thetis was significantly greater than occurrences of T. stigmatica, which was driven by significantly greater occurrences of T. thetis in wet sclerophyll forest. There was both spatial and temporal partitioning between the two species; there was a significant difference in the occurrences of the two species at individual cameras and T. stigmatica had a different activity schedule than T. thetis in wet sclerophyll forest, where the latter reached its greatest rate of occurrence. At a finer (camera station) scale, occurrences of T. thetis increased with proximity to roads and grassy edges and at sites that were less rocky and less steep. T. stigmatica occurrence increased in the presence of rainforest elements like vines, palms and ferns, more ground-level cover and tree-fall gaps and at sites with fewer emergent eucalypts.

Conclusion

Our findings have implications for managing these pademelons and their habitats. T. thetis is a common species that was encountered more often than T. stigmatica, and it responded positively to human disturbance like roadsides and grassy edges, presumably because these areas provided good grazing opportunities. By comparison, T. stigmatica is a threatened species, and it responded to natural disturbance like tree-fall gaps where lateral cover was greater, and where rainforest food plants may be more abundant. Our results suggest, therefore, that conservation of the threatened T. stigmatica requires the preservation of intact rainforest.

Arterial Circle of the Brain of the Red-Necked Wallaby (Notamacropus rufogriseus)

Simple Summary

The red-necked wallaby is a small, herbivorous mammal that is native to Australia. In the study, the anatomy of arterial vessels that transport blood to the brain in this species was described and compared with that of other groups of mammals. The results of this research can contribute to further physiological and pathophysiological studies. This is the first description of this anatomical area that has been carried out in a marsupial species.

Abstract

The red-necked wallaby is a medium-sized marsupial species, which have increasingly been kept as pets around the world. In the study, the arterial blood supply for the brain in this species was described. The study was conducted on 50 specimens with two preparation methods. The main artery supplying the brain was the internal carotid artery. The arterial circle of the brain was closed from the caudal side. The anatomy of the arteries of the described region was compared with other groups of mammals. This is the first description of this anatomical area that has been carried out in a marsupial species. Understanding the anatomy of the circulatory system in the wallaby can be valuable for further physiological and pathophysiological studies.

Comparative Study of Brain Size Ontogeny: Marsupials and Placental Mammals

There exists a negative allometry between vertebrate brain size and body size. It has been well studied among placental mammals but less is known regarding marsupials. Consequently, this study explores brain/body ontogenetic growth in marsupials and compares it with placental mammals. Pouch young samples of 43 koalas (Phascolarctos cinereus), 28 possums (Trichosurus vulpecula), and 36 tammar wallabies (Macropus eugenii) preserved in a solution of 10% buffered formalin, as well as fresh juveniles and adults of 43 koalas and 40 possums, were studied. Their brain size/body size allometry was compared to that among humans, rhesus monkeys, dogs, cats, rats, guinea pigs, rabbits, wild pigs, and mice. Two patterns of allometric curves were found: a logarithmic one (marsupials, rabbits, wild pigs, and guinea pigs) and a logistic one (the rest of mammals).

Morphological pattern of the pes tendons in Bennett's Wallaby (Macropus rufogriseus)

Wallabies are small- to medium-sized hopping marsupials and have large and flexible tendons in their hind limbs that act like springs. This study aimed to show the morphological pattern of the pes tendons in Bennett's wallaby. Two Bennett's Wallabies (Macropus rufogriseus) that died of natural causes have been used for this study. The pes was dissected using standard dissection techniques to expose the tendons around metatarsals and digits. The crural musculature of the hind limb was also dissected to identify the origin of the tendons. Tendons of m. extensor digitorum longus, m. extensor digitorum lateralis, m. extensor digiti II et III longus, m. flexor digitorum superficialis, m. flexor digitorum profundus and mm. interossei were the main identified tendons. Tendons of m. extensor digitorum longus attached to the distal phalanx of the fourth digit. The tendon of m. extensor digitorum lateralis had two insertion points, on the fourth and the fifth digits. The tendon of m. flexor digitorum superficialis bifurcates at the level proximal one-third of the metatarsus. The relatively thinner branch inserted into the phalanx of the fifth digit, while the thicker splits and inserted to the medial and lateral surface of the distal end of the proximal phalanx of the fourth digit. Tendon of m. flexor digitorum profundus was the thickest tendon on the plantar surface, and it had four insertion points, which were the distal phalanges of the second, third, fourth and fifth digits. This study provides detailed information for future studies on the biomechanical and functional morphology of tendons in marsupials.

Non-invasive monitoring and reintroduction biology of the brush-tailed rock-wallaby (

Thirty-nine endangered brush-tailed rock-wallabies (Petrogale penicillata) were reintroduced to Grampians National Park, western Victoria, between 2008 and 2012. Subsequent high mortality, low breeding, and no recruitment were linked to fox predation and physical disturbance during monitoring. From 2014 to 2017, the colony was left undisturbed and monitored only by remote camera. Five adult animals were identified across this period (1 ♂ and 3 ♀s – all tagged; and one untagged female), and an average of 0.7 pouch young were birthed per tagged female per year. In 2019, camera-monitoring and non-invasive genetic monitoring (faecal) were used to identify colony members, genetic diversity, and breeding. Camera monitoring in 2019 identified the same five individuals, whereas genetic monitoring using 12 microsatellites identified eight individuals (two male and six female genotypes). Genetic diversity within the colony was moderate (expected heterozygosity (He) = 0.655, observed heterozygosity (Ho) = 0.854). Leaving the colony undisturbed after 2013 correlated with improved adult survival, increased breeding, and successful recruitment of young to the population. Recommendations for the Grampians colony include continuation of regular camera- and scat monitoring to improve our understanding of the reintroduction biology of P. penicillata and other marsupials in open, unfenced landscapes.

Social evolution in mammals

[Figure: see text].

Landscape-scale effects of homesteads, water, and dingoes on invading chital deer in Australia’s dry tropics

Identifying landscape features and processes that facilitate the persistence of populations is particularly important for invasive mammal species, because it can focus management interventions on relatively small areas. We used camera traps to test predictions concerning the relative abundance of invading chital deer (Axis axis) on seven cattle ranches in northern Australia: that abundance of chital deer would be highest near permanent water and near homesteads, and that dingoes (Canis dingo) reduce abundance of chital deer. Distance from the nearest homestead determined deer abundance (as indexed by images per camera-day), with negligible abundance > 4 km from homesteads. In contrast, distance from homestead did not predict abundance of feral pigs (Sus scrofa), macropods, or dingoes. Abundance of chital deer also declined with increasing distance from water, as did feral pig abundance. There was no relationship between either macropod or dingo abundance and distance to water. The abundance of chital deer was unaffected by dingo abundance, but 75–100% of dingo scats collected within 1 km of homesteads contained chital deer. The high abundances of chital deer near homesteads are likely due to increased food quality or quantity, or protection from dingoes, but these hypotheses require further testing. We conclude that homesteads and permanent water are important determinants of the distribution and abundance of invasive chital deer in northern Australia (i.e., they are “invasion hubs” for this species). Our results suggest that, during the dry season, managers should survey for and attempt to control chital deer within 4 km of homesteads and within 3 km of water.

Mixing Genetically and Morphologically Distinct Populations in Translocations: Asymmetrical Introgression in A Newly Established Population of the Boodie (Bettongia lesueur)

The use of multiple source populations provides a way to maximise genetic variation and reduce the impacts of inbreeding depression in newly established translocated populations. However, there is a risk that individuals from different source populations will not interbreed, leading to population structure and smaller effective population sizes than expected. Here, we investigate the genetic consequences of mixing two isolated, morphologically distinct island populations of boodies (Bettongia lesueur) in a translocation to mainland Australia over three generations. Using 18 microsatellite loci and the mitochondrial D-loop region, we monitored the released animals and their offspring between 2010 and 2013. Despite high levels of divergence between the two source populations (FST = 0.42 and ϕST = 0.72), there was clear evidence of interbreeding between animals from different populations. However, interbreeding was non-random, with a significant bias towards crosses between the genetically smaller-sized Barrow Island males and the larger-sized Dorre Island females. This pattern of introgression was opposite to the expectation that male-male competition or female mate choice would favour larger males. This study shows how mixing diverged populations can bolster genetic variation in newly established mammal populations, but the ultimate outcome can be difficult to predict, highlighting the need for continued genetic monitoring to assess the long-term impacts of admixture.

Circadian rhythms enable efficient resource selection in a human-modified landscape

Animals access resources such as food and shelter, and acquiring these resources has varying risks and benefits, depending on the suitability of the landscape. Some animals change their patterns of resource selection in space and time to optimize the trade-off between risks and benefits. We examine the circadian variation in resource selection of swamp wallabies (Wallabia bicolor) within a human-modified landscape, an environment of varying suitability. We used GPS data from 48 swamp wallabies to compare the use of landscape features such as woodland and scrub, housing estates, farmland, coastal areas, wetlands, waterbodies, and roads to their availability using generalized linear mixed models. We investigated which features were selected by wallabies and determined whether the distance to different landscape features changed, depending on the time of the day. During the day, wallabies were more likely to be found within or near natural landscape features such as woodlands and scrub, wetlands, and coastal vegetation, while avoiding landscape features that may be perceived as more risky (roads, housing, waterbodies, and farmland), but those features were selected more at night. Finally, we mapped our results to predict habitat suitability for swamp wallabies in human-modified landscapes. We showed that wallabies living in a human-modified landscape selected different landscape features during day or night. Changing circadian patterns of resource selection might enhance the persistence of species in landscapes where resources are fragmented and disturbed.

Shedding light on a cryptic macropodid: home ranges and habitat preferences of translocated western brush wallabies (Notamacropus irma)

A salvage translocation of western brush wallabies (Notamacropus irma (Jourdan, 1837)) was a condition of approval to build a new runway at Jandakot Airport, Western Australia. Since little is known about this endemic Western Australian species, the translocation presented a valuable opportunity to gain information on the species after release into Harry Waring Marsupial Reserve, a 260-ha reserve where these animals had been recorded previously. We aimed to gain information on the biology and ecology of the species and follow the movement of individuals tracked with Global Positioning System (GPS) collars over six months to determine their short-term survival, home-range establishment, overlap in home range between individuals, and habitat utilisation in the reserve. Weekly mean home-range estimates did not differ between males (10.0±9.7 (s.d.) ha, 95% KDE, n=6) and females (12.1±6.1 (s.d.) ha, 95% KDE, n=5) (P=0.473). Some males had 67–70% overlap in home ranges with some females, but substantial distances maintained between individuals (from 123±110m to 292±303m) confirmed the solitary nature of the species. Western brush wallabies preferred Banksia spp. woodlands, possibly due to the availability of canopy cover, and some specific understorey associations, such as Hibbertia hypericoides, that form part of their diet. Our study highlighted the importance of understanding the home-range establishment and vegetation preferences of translocated animals that will inform the planning of future translocations.

Dental fluorosis and skeletal fluoride content as biomarkers of excess fluoride exposure in marsupials

Particulate and gaseous fluoride emissions contaminate vegetation near fluoride-emitting industries, potentially impacting herbivorous wildlife in neighboring areas. Dental fluorosis has been associated with consumption of fluoride-contaminated foliage by juvenile livestock and wildlife in Europe and North America. For the first time, we explored the epidemiology and comparative pathology of dental fluorosis in Australian marsupials residing near an aluminium smelter. Six species (Macropus giganteus, Macropus rufogriseus, Wallabia bicolor, Phascolarctos cinereus, Trichosurus vulpecula, Pseudocheirus peregrinus) demonstrated significantly higher bone fluoride levels in the high (n=161 individuals), compared to the low (n=67 individuals), fluoride areas (p<0.001). Necropsy examinations of all six species from the high-fluoride area near the smelter revealed dental lesions considered characteristic of dental fluorosis in eutherian mammals. Within the high-fluoride area, 67% of individuals across the six species showed dental enamel lesions, compared to 3% in the low-fluoride areas. Molars that erupted before weaning were significantly less likely to display pathological lesions than those developing later, and molars in the posterior portion of the dental arcade were more severely fluorotic than anterior molars in all six species. The severity of dental lesions was positively associated with increasing bone fluoride levels in all species, revealing a potential biomarker of excess fluoride exposure.

Hopping Down the Main Street: Eastern Grey Kangaroos at Home in an Urban Matrix

Simple Summary

Eastern Grey Kangaroos (Macropusgiganteus) occur throughout the seaside town of Anglesea in southern Victoria, Australia. We have tagged about half of these kangaroos in a longitudinal study of population dynamics and behavior. A golf course forms the nucleus of this population. Females live on and around the golf course, but males roam across the town in autumn and winter, living in bush reserves, empty blocks and back yards. Most females breed every year, but over half of their young disappear. Vehicles are the major cause of adult deaths, killing a much higher proportion of males than females.

Abstract

Most urban mammals are small. However, one of the largest marsupials, the Eastern Grey Kangaroo Macropusgiganteus, occurs in some urban areas. In 2007, we embarked on a longitudinal study of this species in the seaside town of Anglesea in southern Victoria, Australia. We have captured and tagged 360 individuals to date, fitting each adult with a collar displaying its name. We have monitored survival, reproduction and movements by resighting, recapture and radio-tracking, augmented by citizen science reports of collared individuals. Kangaroos occurred throughout the town, but the golf course formed the nucleus of this urban population. The course supported a high density of kangaroos (2–5/ha), and approximately half of them were tagged. Total counts of kangaroos on the golf course were highest in summer, at the peak of the mating season, and lowest in winter, when many males but not females left the course. Almost all tagged adult females were sedentary, using only part of the golf course and adjacent native vegetation and residential blocks. In contrast, during the non-mating season (autumn and winter), many tagged adult males ranged widely across the town in a mix of native vegetation remnants, recreation reserves, vacant blocks, commercial properties and residential gardens. Annual fecundity of tagged females was generally high (≥70%), but survival of tagged juveniles was low (54%). We could not determine the cause of death of most juveniles. Vehicles were the major (47%) cause of mortality of tagged adults. Road-kills were concentrated (74%) in autumn and winter, and were heavily male biased: half of all tagged males died on roads compared with only 20% of tagged females. We predict that this novel and potent mortality factor will have profound, long-term impacts on the demography and behavior of the urban kangaroo population at Anglesea.

Peace-making in marsupials: the first study in the red-necked wallaby (Macropus rufogriseus)

The issue of reconciliation has been widely investigated in many eutherian mammal species. Nevertheless, no data are available for marsupial mammals. Indeed, the majority of reports focus on group dynamics from an ecological and reproductive perspective, but no study has investigated them from a social point of view. We observed the red-necked wallaby colony (Macropus rufogriseus) hosted at the Tierparc Zoo Berlin (Germany) and collected data on aggressive and post-conflict interactions between group members. We found that the phenomenon of reconciliation is present in the study species (mean group CCT 27.40% ± 8.89% SE). Therefore, we demonstrated, for the first time, the occurrence of reconciliation in a gregarious marsupial mammal. Post-conflict reunion was not affected by the relationship quality between individuals (friendship or kinship) but it was fine-tuned according to the aggression intensity. For example, low intensity conflicts were reconciled whereas high intensity ones were not. Reconciliation reduced anxiety-related scratching in both of the former opponents and limited further attacks towards the victim during the post-conflict period. These findings suggest that the red-necked wallaby, like many eutherian species, can evaluate the costs of reconciliation and engage in peace-making behavior in the right contexts, in order to maximize its pay-offs.

Mating system and local dispersal patterns of an endangered potoroid, the northern bettong (Bettongia tropica)

The northern bettong (Bettongia tropica) (Potoroidae), is an endangered macropod with a restricted distribution. We combined radio-tracking and trapping data with microsatellite genotypes to infer the mating system and local dispersal patterns of this species, and discuss their relevance to translocations. We defined the mating system as ‘overlap promiscuity’ (sensu Wittenberger 1979), though we cannot rule out serial monogamy. We found significant effects of proximity (average distance between parents = 190 m) and male weight, but not size, on the likelihood of paternity, suggesting that closer, heavier males have greater mating success. The average distance between putative pairs of relatives suggested that most dispersal occurred over short distances, with the distance between ‘related’ females significantly lower than that between related males (0.9 km versus 1.3 km). A spatial autocorrelation analysis showed high female relatedness across distances of up to 435 m, equivalent to half an average home range width. Conversely, male pairs had low relatedness across 0 to 870 m. These results suggested that female young often settle next to their mother, while males avoid nesting within their father’s home range. Both limited natal and ‘mating’ dispersal may have contributed to the strong genetic structure previously reported for this species.

The genetic mating system of the long-nosed potoroo (Potorous tridactylus) with notes on male strategies for securing paternity

The potoroids are a small group of cryptic macropodoid marsupials that are difficult to directly monitor in the wild. Consequently, information regarding their social and mating systems is limited. A population of long-nosed potoroos (Potorous tridactylus) on French Island, Victoria, was monitored from June 2005 to August 2010. Tissue samples were collected from 32 (19 ♂, 13 ♀) independent potoroos and 17 pouch young. We aimed to determine the genetic mating system and identify patterns of paternity through genotyping individuals at 10 microsatellite loci. Additionally, we investigated the importance of body mass and site residency as strategies in securing paternity. Twelve of the 17 pouch young sampled were assigned paternity with confidence to five males. Multiple pouch young were sampled from two long-term resident females, one of which had 10 pouch young sired by multiple partners, with some repeat paternity, while the other had three young sired by one male, suggesting that the mating system is not entirely promiscuous. Sires were recorded on site for significantly longer periods than non-sires but were not significantly larger than non-sires at conception. This suggests that sires employ strategies other than direct competition, such as scramble competition, to secure paternity in P. tridactylus.

Dominance, body size and internal relatedness influence male reproductive success in eastern grey kangaroos (Macropus giganteus)

Knowledge of the determinants of reproductive success is essential for understanding the adaptive significance of particular traits. The present study examined whether particular behavioural, morphological, physiological or genetic traits were correlated with male dominance and reproductive success using three semi-free-ranging captive populations (n = 98) of the eastern grey kangaroo (Macropus giganteus). The morphological traits measured included bodyweight, head, forearm, tail, pes and leg length, forearm and bicep circumference, and testis size. Blood samples were collected to determine serum testosterone concentrations. All individuals were typed for 10 microsatellite loci and paternity determined for each pouch young. To determine the influence of relatedness and genetic diversity on male reproductive success, internal relatedness, standardised heterozygosity and mean d2 were calculated. Dominant males sired a significantly higher proportion of offspring than smaller, lower-ranked males and had higher testosterone concentrations. Males that sired offspring were significantly heavier and had larger body size. Sires were significantly more heterozygous and genetically dissimilar to breeding females than non-sires. Despite the wealth of knowledge on the social organisation of kangaroos, this is the first study to assign parentage and male reproductive success using molecular evidence.

Behavioural ecology of red and grey kangaroos: Caughley's insights into individuals, associations and dispersion

In 1964, Graeme Caughley published two papers on the activity, density, dispersion and social organisation of kangaroos. He made direct observations of the behaviour of two species, and used measures of their faecal pellets to infer habitat use. This work paved the way for many studies of the behaviour of individual kangaroos, the associations between them, and the dispersion of individuals within a population. At an individual level, activity budgets of kangaroos are now known to be influenced by extrinsic factors such as weather, season, and forage conditions, as well as intrinsic factors such as sex and reproductive status. Habitat selection is understood in terms of the requirement for both food and horizontal cover, and past predation continues to play a role in the use of cover, as Caughley first proposed. At the level of associations among individuals, group size is positively related to population density, as Caughley predicted, but is also influenced by habitat structure. Contrary to his views, the high rate of group flux does not represent random movement of individuals. Instead, there are subtle yet persistent associations between related individuals. There is also strong dissociation between population classes when sexual segregation occurs during the non-mating period in seasonally breeding populations. Despite these effects, kangaroos are only weakly constrained by social factors, suggesting that population dispersion may conform to ideal free distribution when food resources are limited. At a management level, this suggests that kangaroos have the potential to redistribute rapidly after culling programs aimed at reducing density in overabundant populations.

Fertility control in female eastern grey kangaroos using the GnRH agonist deslorelin. 2. Effects on behaviour

In recent years fertility control has been proposed as an ethically acceptable alternative to lethal control techniques when managing overabundant kangaroo populations. A promising non-steroidal, non-immunological approach to contraception in female kangaroos involves the use of slow-release implants containing the gonadotrophin-releasing hormone (GnRH) agonist deslorelin. The practicality of using deslorelin implants as a management option is dependant on its effective inhibition of reproduction without negative physical or behavioural side-effects. This study investigated the behavioural effects of deslorelin implants in female eastern grey kangaroos. Treatment had no detectable effects on crepuscular activity. Alterations in the frequency of sexual interactions were observed in deslorelin-treated females, with a behavioural oestrus induced ~3 days after combined removal of pouch young and deslorelin administration. Copulation was observed during this early oestrous period, but conception was not achieved and pouch young were not observed in any treated females. Control females gave birth within 69.6 ± 10.4 days (mean ± s.e.m., n = 9) of placebo implant administration. The first births observed in treated animals were on Days 510, 637 and 643 after treatment. The remaining seven treated animals had not bred by the end of the study, a period of 647 days.

Evolution of sexual segregation in mammalian herbivores: kangaroos as marsupial models

Sexual segregation is best known in sexually dimorphic ungulates. Many hypotheses have been proposed to explain the evolution of sexual segregation in ungulates, but all are reducible to the influence of two factors: body size and sex-specific reproductive strategy. Definitive tests of these hypotheses are lacking in ungulates because these factors are confounded, all males being somewhat larger than females. Kangaroos represent a parallel radiation of terrestrial herbivores, but their populations are composed of a spectrum of adult body sizes, ranging from small males the same size as females to large males more than twice the size. We exploited this heteromorphism to assess the independent influences of size and sex in these ungulate analogues. We conducted a preliminary study of western grey kangaroos (Macropus fuliginosus) in north-western Victoria, Australia. Adult males predominately occupied grassland habitat, whereas females occurred mostly in lakebed, woodland and shrubland. Single-sex groups occurred more often than expected during the non-mating season. The diet of large males had the highest proportion of grass, and females had the least. These initial results indicate that both size and sex influence segregation in this species, confirming the worth of kangaroos as marsupial models for research into the evolution of sexual segregation.

Body size, age and paternity in common brushtail possums (Trichosurus vulpecula)

Sexual selection should produce sexual size dimorphism in species where larger members of one sex obtain disproportionately more matings. Recent theory suggests that the degree of sexual size dimorphism depends on physical and temporal constraints involving the operational sex ratio, the potential reproductive rate and the trade-off between current reproductive effort and residual reproductive value. As part of a large-scale experiment on dispersal, we investigated the mating system of common brushtail possums inhabiting old-growth Eucalyptus forest in Australia. Paternity was assigned to 20 of 28 pouch-young (maternity known) genotyped at six microsatellite loci. Male mating success was strongly related to body size and age; male body weight and age being highly correlated. Despite disproportionate mating success favouring larger males, sexual size dimorphism was only apparent among older animals. Trapping and telemetry indicated that the operational sex ratio was effectively 1 : 1 and the potential reproductive rate of males was at most four times that of females. Being larger appeared to entail significant survival costs because males 'died-off' at the age at which sexual size dimorphism became apparent (8-9 years). Male and female home ranges were the same size and males appeared to be as sedentary as females. Moreover, longevity appears to be only slightly less important to male reproductive success than it is to females. It is suggested that a sedentary lifestyle and longevity are the key elements constraining selection for greater sexual size dimorphism in this 'model' medium-sized Australian marsupial herbivore.

Convergent maternal care strategies in ungulates and macropods

Mammals show extensive interspecific variation in the form of maternal care. Among ungulates, there is a dichotomy between species in which offspring follow the mother ("following" strategy) versus species in which offspring remain concealed ("hiding" strategy). Here we reveal that the same dichotomy exists among macropods (kangaroos, wallabies and allies). We test three traditional adaptive explanations and one new life history hypothesis, and find very similar patterns among both ungulates and macropods. The three traditional explanations that we tested were that a "following" strategy is associated with (1) open habitat, (2) large mothers, and (3) gregariousness. Our new life-history hypothesis is that a "following strategy" is associated with delayed weaning, and thus with the "slow" end of the slow-fast mammalian life-history continuum, because offspring devote resources to locomotion rather than rapid growth. Our comparative test strongly supports the habitat structure hypothesis and provides some support for this new delayed weaning hypothesis for both ungulates and macropods. We propose that sedentary young in closed habitats benefit energetically by having milk brought to them. In open habitats, predation pressure will select against hiding. Followers will suffer slower growth to independence. Taken together, therefore, our results provide the first quantitative evidence that macropods and ungulates are convergent with respect to interspecific variation in maternal care strategy. In both clades, differences between species in the form of parental care are due to a similar interaction between habitat, social behavior, and life history.

Do big-brained animals play more? Comparative analyses of play and relative brain size in mammals

It has been hypothesized that play is more likely to be present in larger brained species. We tested this hypothesis in mammals using independent contrasts, a method that controls for phylogenetic relatedness. Comparisons across 15 orders revealed that the prevalence and complexity of play was significantly correlated with brain size, with larger brained orders having more playful species. Three orders, Rodentia, Marsupialia, and Primates, were used for within-order comparisons among species and, where possible, among families. The comparisons were not significant for rodents or primates, and those for marsupials yielded inconsistent results. Therefore, although a strong relationship is present at the highest taxonomic level of comparison, it diminishes or evaporates at lower level comparisons.

Effects of body size and home range on access to mates and paternity in male bridled nailtail wallabies

The bridled nailtail wallaby, Onychogalea fraenata, is a relatively small, solitary and sexually size dimorphic macropod. We studied the mating system of free-ranging wallabies over 3 years, using microsatellite analysis of paternity, radiotelemetry and behavioural observations. Both sexes were promiscuous, and general reproductive behaviour was similar to that of larger, better-known macropods. Home range size influenced the number of associations with oestrous females, and was a significant component of male reproductive success. Female population density varied within the site, but males with home ranges that overlapped more females did not sire more offspring. Aggression between males occurred only around oestrous females and males did not establish a predetermined dominance hierarchy. Male body weight strongly influenced priority of access to oestrous females, and was related to age. The number of times that males were seen closest to an oestrous female when other males were present (priority of access) was the most important predictor of variation in the number of offspring sired. Females mated with several males within and between oestrous cycles, and may have influenced male-male competition by prolonging advertisement of approaching oestrus, expanding their home ranges at oestrus and engaging in mate chases that attracted groups of up to six males. Despite overall similarities in the mating system of this species and that of other macropods, male mating success may be less skewed in bridled nailtail wallabies than in other species, although paternity analysis of free-ranging populations of other species is required to confirm this conclusion. Copyright 1999 The Association for the Study of Animal Behaviour.