Background: We still do not understand the key drivers or prevalence of genetic monogamy in mammals despite the amount of attention that the evolution of mammalian monogamy has received. There have been numerous reviews of the hypotheses proposed to explain monogamy, some of which focused on animals in general, while others focused on particular classes like birds or mammals, or on specific orders within a class. Because monogamy is rare in mammals overall but relatively common in some of the orders in which it has been observed (e.g., Primates, Macroscelidea, and Carnivora), mammals provide a unique taxon in which to study the evolution and maintenance of monogamy However, the term "monogamy" encompasses related but separate phenomena; i.e., social monogamy (pair-living by opposite-sex conspecifics) and genetic monogamy or reproductive monogamy (mating exclusivity). A recent review of mammalian monogamy reported that 226 species (9%) in 9 orders (35%) were socially monogamous, although socially monogamous mammals are not necessarily genetically monogamous.Methods: Since factors that predispose socially monogamous mammals to be genetically monogamous are still subject to debate, we conducted meta-analyses using model selection to determine the relative importance of several life history, demographic, and environmental factors in predicting genetic monogamy. Results:We found sufficient data to include 41 species in our analysis, about 2x more than have been included in previous analyses of mammalian genetic monogamy. We found that living as part of a socially monogamous pair vs. in a group was the best predictor of genetic monogamy, either by itself or in combination with high levels of paternal care. A male-biased sex ratio and low population density were inversely related to the number of pairs that were genetically monogamous, but not to the production of intra-pair young or litters. Conclusion:Our results agree with the results of some previous analyses but suggest that more than one factor may be important in driving genetic monogamy in mammals.

Comparative studies aid in our understanding of specific conditions favoring the initial evolution of different types of social behaviors, yet there is much unexplained intraspecific variation in the expression of social behavior that comparative studies have not yet addressed. The proximate causes of this individual variation in social behavior within a species have been examined in some species but its fitness consequences have been less frequently investigated. In this study, we quantified the fitness consequences of variation in the sociality of prairie voles (Microtus ochrogaster). We characterized sociality of voles in semi-natural enclosures using an automated behavioral tracking system paired with social network analyses to quantify the degree of spatial and temporal co-occurrence of different voles. We then assessed the relationship between sociality with mating success (number of different conspecifics with which an individual produced offspring) and reproductive success (total number of offspring surviving to first capture). We measured the number of social connections each individual had with all voles and only with opposite-sex voles by calculating unweighted degree through social network analyses.Both female and male voles varied in the number of social connections they had with all conspecifics and with opposite-sex conspecifics. Voles with an intermediate number of social connections with voles of both sexes had higher mating success overall. In our analyses that considered all social connections with voles of both sexes, voles with an intermediate number of social connections produced more offspring. Males with a very high or low number of social connections also had the lowest average body mass. Overall, our results suggest some limit on the fitness benefits of sociality. Although there was substantial individual-variation in our measure of vole social behavior, intermediate levels of social connections may be most favorable.

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The combined effects of global climate change and increased anthropogenic use of free water are likely to cause decreases in availability and surface area of water in arid environments. Climate change and water loss are predicted to alter community dynamics, but identifying mechanisms underlying differential responses of species remains a critical conservation challenge. Bats drink in flight and rely on accessible water sources, yet the ability to access water is a function of flight maneuverability. By reducing the size of water sources (to simulate predicted water loss due to climate change/increased human use), we demonstrated species-specific responses by desert bats based on differences in morphology and flight maneuverability. Under natural conditions, lessmaneuverable bats selected larger water sources while maneuverable bats exhibited no preference. When we experimentally reduced surface area, larger, less-maneuverable bats experienced a 69% decrease in proportion of drinking passes (p < 0.05) and increased competition with smaller, maneuverable bats. Our study illustrates how morphology can mediate access to a resource and highlights conservation implications as water becomes more limited in arid environments. Selection for differences in wing morphology and flight ability in insectivorous bats has allowed for coexistence and high species richness at a local scale. However, anticipated reductions in the sizes of water sources due to climate disruption may lead to species with less maneuverability being unable to access water efficiently and facing increased competition from more agile bats.