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Seasonal variation in food resources and predation risk imposes major constraints on herbivores, which must adjust their behaviour to maximize their energy intake and survival. In seasonally driven landscapes, it is not yet clear what the primary drivers are that shape seasonal variation in vigilance and feeding rates. These rates have been shown to vary in relation to various environmental, social and individual factors, but many of these factors also vary through the year, due to variation in food supply. We studied wild female eastern grey kangaroos, Macropus giganteus , under low predation risk over a year to investigate whether vigilance and feeding rates varied seasonally and whether this variation was mainly driven by food quantity or quality, group size or individuals' reproductive states. Both vigilance and feeding rates varied seasonally, as did food quantity and quality and group size. Vigilance, including antipredator (head orientation away from the group) and exclusive (i.e. vigilance without chewing) vigilance, decreased and feeding rate increased with increasing group size. However, because group size increased with food quality and quantity, food resources emerged as the primary driver of variation in behavioural strategies. These results suggest that the observed effects of group size on the trade-off between food acquisition and safety are in fact corollaries of the seasonal variation in food supply in our study system, in which the risk of predation on adults is low, and hence are by-products of the foraging choices made by kangaroos in response to the dynamics of the quantity and quality of food. [ABSTRACT FROM AUTHOR]

Sociability, how individuals interact with conspecifics, is considered to be a key axis of animal personality. Consistent differences between individuals in measures of sociability have been demonstrated in some taxa, yet individuals also exhibit plasticity in their sociability across differing ecological conditions, particularly in gregarious species that do not occur in stable cohesive groups. Although repeatability and plasticity of measures of sociability are both important for understanding animal personality they have rarely been studied concurrently. Between and even within species, multiple behaviours have been considered to represent sociability, but there is still little understanding of the degree to which different measures of sociability reflect distinct traits. In this study, our first aim was to determine the repeatability of four different measures, representing two broad aspects of individual females' sociability, in a wild population of eastern grey kangaroos, Macropus giganteus . Our second aim was to investigate how shorter-term environmental conditions and individuals' states related to plasticity in these measures. Using data collected each month over a 5-year period on over 100 adult females, we analysed factors contributing to variation in individuals' grouping patterns (to reflect general gregariousness) and in the number of different conspecifics with which individuals associated (their ‘choosiness’ of social partners). Rainfall, body condition and reproductive state were all related to females' mean group sizes, and females with older dependent young foraged further from their neighbours. Females were more selective about group members when there was more food, and when they were in poor or excellent body condition. Although social preferences exist among females in this population, and females' measures of sociability are repeatable and differ between individuals over the long term, these current findings suggest that the influences of individuals' states and environmental conditions contribute to variation in females' patterns of sociability over shorter periods. [ABSTRACT FROM AUTHOR]

Social relationships established early in life can have effects on social structure and influence individual fitness. Eastern grey kangaroos, Macropus giganteus , nurse their young for at least 18 months, allowing for a strong bond to develop between mothers and young. Because most female kangaroos are philopatric, the mother-offspring relationship established during lactation could persist into adulthood, resulting in clusters of female kin. Strong social bonds, however, are based on affiliative behaviours and frequent interactions. In particular, one might not expect strong bonds among related individuals unless there are advantages to interacting with relatives compared to associating with unrelated conspecifics. We examined development of the mother-offspring relationship in eastern grey kangaroos from permanent emergence from the pouch to the time of weaning. We studied a high-density population at Wilsons Promontory National Park, Victoria, Australia. There were few differences in the behaviour of sons and daughters towards mothers. However, daughters foraged slightly closer than sons to their mothers and daughters were weaned approximately 2 months later than sons if the mother did not have a surviving large pouch young. Mothers associated more closely with their daughters than their sons when offspring were aged 10–29 months but neither sex associated closely with their mothers beyond 33 months of age. Mothers never intervened to defend their young from aggressive individuals and it was the offspring that maintained spatial proximity to their mothers. Kangaroo mothers had few interactions with their juvenile offspring other than nursing. Females may be philopatric and settle near close kin as adults but kangaroos appear to have few of those early affiliative interactions necessary for social bonds to develop. [ABSTRACT FROM AUTHOR]

Understanding the relationship between kinship and female social preferences in mammalian societies is frequently complicated by philopatric behaviour and variation in pairwise home range overlap. While the influence of space use on association patterns is increasingly being considered in studies using network analysis, methods are needed for generating null models that control for pairwise home range overlap. We investigated female associations in a wild population of eastern grey kangaroos, Macropus giganteus, a species with higher fission–fusion dynamics, to test the influences of home range overlap and kinship on pairwise association strengths. Genetic analysis revealed that females were highly philopatric and we found that association strengths were significantly correlated with home range overlap. To test for social preferences, we compared observed associations with random associations based on individuals' space use, simulated using Digiroo2. HWIG, a version of the half-weight association index that controls for among-individual variation in gregariousness was used for all analyses. Preferred associates had significantly higher pairwise relatedness than expected. Although some females had strong social relationships with some of their close kin, in general, space use had a much stronger correlation with association strengths than both pairwise relatedness and maternal lineage. This suggests that familiarity may play a key role in driving association patterns in female kangaroos. We recommend controlling for individuals' space use when undertaking studies on social preferences and social structure in general. [ABSTRACT FROM AUTHOR]

Communities, clusters of individuals who interact socially primarily with each other, are fundamental elements of social structure in many species. Community membership can be influenced by spatial factors and by social preferences resulting from genetic or phenotypic assortment or shared behavioural strategies. Very little is known about community social structure in herbivorous mammals with higher fission–fusion dynamics, which are societies in which group membership frequently changes. Using network analysis on data from 171 wild female eastern grey kangaroos, Macropus giganteus, a species exhibiting these foraging and social attributes, we quantified the presence of significant, strong community structure. Lagged association rates confirmed the temporal stability of this intermediate-level social tier. Communities' home ranges overlapped considerably, but their core home ranges were more dispersed, suggesting some influence of spatial factors on community membership. However, community-level social assortment was maintained in areas in which core home ranges overlapped, even though communities used these areas simultaneously, implying that social preferences also influence the presence of communities in female kangaroos. Within-community pairwise relatedness levels based on microsatellite markers were somewhat higher than those across the population, probably because of philopatry, but mitochondrial DNA revealed that communities did not reflect matrilines. This study contributes to the growing literature attempting to understand the factors driving fission–fusion social dynamics by showing that extensive home range overlap among communities can occur in the absence of behaviours usually associated with the maintenance of social preferences. [ABSTRACT FROM AUTHOR]

In mammals, lactation is the most energetically demanding component of female reproduction. Theory predicts an increase in food intake by lactating females, but very few studies have used contraceptives to experimentally test the influence of reproduction on foraging behaviour of wild mammals. From 2009 to 2011, we observed 182 individually marked female eastern grey kangaroos, Macropus giganteus, in two populations, including 29 that received an experimental contraceptive treatment. We sought to determine whether lactating females increase their foraging rate compared to contracepted and naturally nonlactating females. The proportion of time spent foraging during 10min focal samples did not vary according to reproductive status in one population. In the other, lactating females spent 4% less time feeding than nonlactating females. Day and midday activity and bite and chewing rates were higher in lactating than in nonlactating females. Bite rate increased with the size of the pouch young and was higher for mothers of sons than for mothers of daughters. Bite rate was also affected by reproductive effort in the previous year, being higher for females that had weaned a young. Foraging behaviour was independent of body mass and group size, but bite rate appeared to decrease with female age. In one population, we found strong effects of date and year on foraging behaviour. Our study is a rare experimental manipulation of reproduction in free-ranging large mammals. We found that foraging behaviours were affected by both previous and current reproductive effort and varied with individual characteristics and environmental conditions. [ABSTRACT FROM AUTHOR]

Abstract: Nematodes resembling Macroponema comani, a common parasite of eastern grey kangaroos, Macropus giganteus, in eastern Australia were collected from an unexpected host species, the northern wallaroo, Macropus robustus woodwardi, in the Northern Territory, representing a highly disjunct occurrence. Although these specimens showed no morphological differences when compared with Ma. comani from M. giganteus, sequencing of the first and second internal transcribed spacers ITS-1 and ITS-2 of the nuclear ribosomal DNA revealed seven base pair differences in each spacer region between the two taxa. These differences included a number of autapomorphies. Sequences from both taxa differed significantly from those of Ma. beveridgei, a common parasite of the common wallaroo, Macropus robustus robustus and the euro, M. robustus erubescens. Based on these findings, the specimens in M. r. woodwardi are considered to represent a crypic species. [Copyright &y& Elsevier]

Little is known about the determinants of females'' social interactions in species with fission–fusion social organization, in which individuals associate with different individuals at different times. Even less is known about social organization in marsupials. We investigated the association patterns of wild female eastern grey kangaroos in southeast Queensland. Female kangaroos had a nonrandom social structure and we present a new methodology for analysing social structure that accounts for the amount of spatial overlap shared by pairs of female kangaroos. This simulation model showed that patterns of association among our female kangaroos were not simply those predicted by their patterns of spatial overlap. Females that associated frequently with certain associates were able to graze for longer because they were less vigilant, and thus were able to benefit from having frequent associates. Female kangaroo social structure was affected by the loss of key members of the society during a period of unusually high predation. Information-theoretical modelling showed that the factors affecting grazing behaviour changed after partial population turnover, with the strength of association between nearest neighbours having a positive effect on grazing behaviour before population turnover and group size having a positive effect on grazing behaviour after population turnover. We propose that social organization within this marsupial is more structured than previously thought. [Copyright &y& Elsevier]

Vigilance activity is usually considered an adaptive advantage of group living conferring protection against predators. An individual of a prey species is assumed to benefit from an increase in the number of group members by reducing its own investment in vigilance. However, the proximate mechanism generating the decrease in vigilance with increasing group size is unclear. Most models of this relation assume that either individuals coordinate their scans in nonoverlapping bouts of vigilance or animals scan independently of one another. We studied the relation between vigilance and group size in the eastern grey kangaroo, Macropus giganteus, analysing vigilance at two structural levels, individual vigilance and collective vigilance of the group. We tested both assumptions, coordination and independence of scanning. The time that an individual spent vigilant decreased with group size. However, the time during which at least one individual in the group scanned the environment (collective vigilance) increased up to a group size of seven individuals but decreased thereafter. Analyses revealed that individuals neither coordinated their scanning in an asynchronous way nor scanned independently of one another. On the contrary, both the onset and the end of individuals'' scanning bouts were synchronized between group members, producing waves of collective vigilance. Bouts of vigilance and nonvigilance activity tended to be synchronized. Our results appear to support a hypothesis of allelomimetic vigilance. [Copyright &y& Elsevier]

Examines the behavior response of eastern grey kangaroos, Macropus giganteus to the risks of predation posed by an introduced predator species, Vulpes vulpes. Foraging closer to refuge; Increase of group size by kangaroos; Tendency of females with young at foot to forage alone or in smaller groups.