Open habitats promote female group formation in a solitary ungulate: the Japanese serow

Genetic Analysis Reveals Dispersal Patterns of Japanese Serow in Two Different Habitats of a Mountainous Region

Dispersal increases the costs of feeding and predation risk in the new environment and is reported to be biased toward habitats similar to the natal region in some mammals. The benefits and costs of dispersal often differ between sexes, and most mammals show male-biased dispersal in relation to a polygamous mating system. Japanese serow is generally a solitary and monogamous species. However, recent studies have shown that the sociality of serows on Mt. Asama differs between habitat types. In the mountain forests with low forage availability, solitary habits and social monogamy were observed, while, in alpine grasslands, female grouping and social polygyny were observed, which is probably due to abundant forage availability. We investigated the effects of habitat characteristics and sociality on the dispersal of serows using fecal and tissue samples from two different habitats on Mt. Asama. The Fst value between the two areas was significantly positive, and the mean relatedness within areas was significantly higher than that between areas, which suggests limited gene flow and natal habitat-biased dispersal. Bayesian clustering analysis showed unidirectional gene flow from forest to grassland, which was probably due to the high forage availability of the grassland. Analyses of the assignment index and mean relatedness did not show male-biased dispersal, even in the grassland, where serows were polygynous. Thus, polygyny in the grassland is not linked to male-biased dispersal. In summary, our study suggests that dispersal patterns in Japanese serows are affected by habitat rather than social differences.

Development of Genetic Markers for Sex and Individual Identification of the Japanese Giant Flying Squirrel (Petaurista leucogenys) by an Efficient Method Using High-Throughput DNA Sequencing

DNA markers that detect differences in the number of microsatellite repeats can be highly effective for genotyping individuals that lack differences in external morphology. However, isolation of sequences with different microsatellite repeat numbers between individuals has been a time-consuming process in the development of DNA markers. Individual identification of Japanese giant flying squirrels (Petaurista leucogenys) has been challenging because this species is arboreal and nocturnal and exhibits little to no morphological variation between individuals. In this study, we developed DNA markers for sex and individual identification of this species by an efficient method using high-throughput DNA sequence data. Paired-end 5 Gb (2 × 250 bp) and 15 Gb (2 × 150 bp) genome sequences were determined from a female and a male Japanese giant flying squirrel, respectively. We searched SRY and XIST genes located on Y and X chromosomes, respectively, from high-throughput sequence data and designed primers to amplify these genes. Using these primer sets, we succeeded to identify the sex of individuals. In addition, we selected 12 loci containing microsatellites with different numbers of repeats between two individuals from the same data set, and designed primers to amplify these sequences. Twenty individuals from nine different locations were discriminated using these primer sets. Furthermore, both sex and microsatellite markers were amplified from DNA extracted non-invasively from single fecal pellet samples. Based on our results for flying squirrels, we expect our efficient method for developing non-invasive high-resolution individual- and sex-specific genotyping to be applicable to a diversity of mammalian species.

The Potential for Physiological Performance Curves to Shape Environmental Effects on Social Behavior

As individual animals are exposed to varying environmental conditions, phenotypic plasticity will occur in a vast array of physiological traits. For example, shifts in factors such as temperature and oxygen availability can affect the energy demand, cardiovascular system, and neuromuscular function of animals that in turn impact individual behavior. Here, we argue that nonlinear changes in the physiological traits and performance of animals across environmental gradients—known as physiological performance curves—may have wide-ranging effects on the behavior of individual social group members and the functioning of animal social groups as a whole. Previous work has demonstrated how variation between individuals can have profound implications for socially living animals, as well as how environmental conditions affect social behavior. However, the importance of variation between individuals in how they respond to changing environmental conditions has so far been largely overlooked in the context of animal social behavior. First, we consider the broad effects that individual variation in performance curves may have on the behavior of socially living animals, including: (1) changes in the rank order of performance capacity among group mates across environments; (2) environment-dependent changes in the amount of among- and within-individual variation, and (3) differences among group members in terms of the environmental optima, the critical environmental limits, and the peak capacity and breadth of performance. We then consider the ecological implications of these effects for a range of socially mediated phenomena, including within-group conflict, within- and among group assortment, collective movement, social foraging, predator-prey interactions and disease and parasite transfer. We end by outlining the type of empirical work required to test the implications for physiological performance curves in social behavior.