An increase in variation in the 24 h pattern of body temperature (heterothermy) in mammals can be induced by energy and water deficits. Since performance traits such as growth and reproduction also are impacted by energy and water balance, we investigated whether the characteristics of the body temperature rhythm provide an indication of the reproductive success of an individual. We show that the amplitude of the daily rhythm of body temperature in wild rabbits () prior to breeding is inversely related to the number of pregnancies in the subsequent seven months, while the minimum daily body temperature is positively correlated to the number of pregnancies. Because reproductive output could be predicted from characteristics of the core body temperature rhythm prior to the breeding season, we propose that the pattern of the 24 h body temperature rhythm could provide an index of animal fitness in a given environment.

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Context Social structure of group-living animals has important implications for processes such as gene flow, information transfer, resource utilisation, and disease spread. However, due to the difficulties associated with measuring relationships among wild animals and deriving meaningful estimates of social structure from these interactions, quantifying sociality of evasive species can be challenging. Aims Our aim was to quantify the pattern of social interactions among free-ranging European wild rabbits (Oryctolagus cuniculus) in a temperate region of Australia. Methods We used proximity logging devices to collect data on the dyadic interactions among two populations of rabbits. We then applied recently developed social structure and network analytical techniques to infer estimates of sociality and contact networks from recorded interactions. Key results We found large heterogeneities in the strength of association indices and network centrality measures within but not between populations. Network analytical techniques revealed clustering of rabbits into distinct social groups. Conclusions Most associations within social groups were strong and highly stable over time whereas interactions between groups were rare and transient, indicating low levels of inter-group mixing. Despite the apparent differences in habitat quality between sites, the network characteristics were extremely similar between the two populations. Implications Our results highlight the importance of heterogeneities in individual behaviour in determining the dynamics of directly transmitted diseases at the population level.

There is growing recognition that humans may mediate the strength and nature of the ecological effects of large predators. We took advantage of ongoing gray wolf (Canis lupus Linnaeus, 1758) recolonization in Washington, USA, to contrast adult survival rates and sources of mortality for mule deer (Odocoileus hemionus (Rafinesque, 1817)) and white-tailed deer (Odocoileus virginianus (Zimmermann, 1780)) in areas with and without wolf packs in a managed landscape dominated by multiple human uses. We tested the hypothesis that the addition of wolves to the existing predator guild would augment predator-induced mortality rates for both ungulates. Source of mortality data from adult mule deer and white-tailed deer, respectively, revealed that wolf-related mortality was low compared with that inflicted by other predators or humans. Predator-caused mortality was largely confined to winter. There was little effect of wolf presence on adult deer mortality rates, and there was no difference in mortality between the two deer species relative to wolf-free or wolf-occupied sites. Although this study occurred early in wolf recovery in Washington, our results differ from those demonstrated for gray wolves in protected areas. Thus, we encourage further investigation of effects of direct predation by recolonizing large carnivores on prey in human-dominated landscapes.

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