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We investigated concentrations of blood total mercury (THg) in three extant populations of endangered Whooping Crane (Grus americana). Blood THg was greater in cranes reintroduced during 2001-2008 that range in the eastern US (median = 0.31 ug/g ww) than both wild cranes in central North America (median = 0.11 ug/g ww) and from captivity (median = 0.01 ug/g ww). The median THg blood concentrations in the two free-ranging populations of Whooping Cranes were low compared to reproductive toxic thresholds suggested for other large bird species (> 4.3 ug/g ww), but a singular elevated concentration was observed in one crane (1.04 ug/g ww; 6% of samples from the reintroduced population). These results likely reflect variable dietary Hg exposure among these populations, but should prompt additional biomonitoring to discern risk of greater Hg exposure nearer to the time of breeding and potential effects on productivity.

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Increased housing of wild nonhuman animals in captivity for conservation, research, and rehabilitation has revealed the importance of systematically analyzing effects of the captive environment on behavior. This study focused on the effects of complexity and time held in captivity on foraging behaviors of wild-caught, adult meadow voles (Microtus pennsylvanicus). Forty-six individuals captured from a meadow outside Oshkosh, WI, were assigned to 1 of 4 captive treatment groups: simple/<50 days (SS), simple/>50 days, complex/<50 days, and complex/>50 days. Number of dish visits, proportion foraging, and frequency of nonforaging behaviors recorded during a 15-min foraging trial were measured for all subjects. Kruskal-Wallis and Mann-Whitney U Tests were conducted to analyze 4 different comparisons within this behavioral data. Overall, neither time in captivity or environmental complexity affected nonforaging behaviors. In contrast, foraging behaviors did change with treatment: Voles were less active at food dishes and visited control dishes more in treatment group SS than in the other treatment groups. In addition, sex-related differences in foraging behaviors were maintained when voles were exposed to environmental complexity. This article includes options for wildlife managers to adapt captive environments to meet the welfare and behavioral needs of translocated wild nonhuman mammals.

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In laboratory studies, hamsters (Mesocricetus spp.) exhibit intense male-male aggression, thus making them an excellent model system for studies of the functional and mechanistic bases of aggression. In a field study of golden hamsters (M. auratus) in the wild, however, the few documented male-male interactions were not highly aggressive. Thus, we tested the hypothesis that familiarity modulates aggression in hamsters. Previous investigations of the effects of familiarity on aggression have mostly involved familiarization of unfamiliar individuals through agonistic interactions. Here we allowed male Turkish hamsters (M. brandti) to become familiar with each other by housing them together but separated by a wire-mesh partition (thus 'non-agonistic' familiarity). We found that although non-agonistic familiarity did not decrease investigation of the familiar male, it did decrease the occurrence of fights, the number of fights, and the percentage of time fighting; it also increased the latency to fight. These results are consistent with the 'dear enemy' hypothesis, which proposes that males are less aggressive toward familiar neighbors than to unfamiliar conspecifics because previous interactions have provided enough information about the other individual to render severe aggression unnecessary. Most importantly, our results suggest that information gained about other individuals through non-agonistic interactions decrease the frequency and intensity of fights with those individuals. We conclude that results from laboratory studies on aggression that do not consider the kind of social interactions that individuals have in nature should be interpreted with caution.

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Daily activity rhythms are nearly universal among animals and their specific pattern is an adaptation of each species to its ecological niche. Owing to the extremely consistent nocturnal patterns of activity shown by golden hamsters (Mesocricetus auratus) in the laboratory, this species is a prime model for studying the mechanisms controlling circadian rhythms. In contrast to laboratory data, we discovered that female hamsters in the wild were almost exclusively diurnal. These results raise many questions about the ecological variables that shape the activity patterns in golden hamsters and the differences between laboratory and field results.

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