Natal features (e.g. Julian birth date and birth mass) often have fitness consequences and can be influenced by endogenous responses by the mother to seasonal fluctuations in nutritional quality and photoperiodic cues. We sought to further understand the biological and environmental factors that influence the natal features of a polytocous species in an environment with constant nutritional resources and limited seasonal variation. During a 36-year study we assessed the influence of biological factors (maternal age and litter type [i.e., litter size and sexual composition]) and environmental factors (total precipitation and mean maximum temperature during months encompassing conception, the last trimester of gestation, and the entire length of gestation) on Julian birth date and birth mass using linear-mixed effects models. Linear and quadratic functions of maternal age influenced both natal features with earliest Julian birth dates and heaviest birth masses occurring at prime-age and older individuals, which ranged from 5–9 years of age. Litter type influenced Julian birth date and birth mass. Interestingly, environmental factors affected Julian birth date and birth mass even though mothers were continuously allowed access to a high-quality diet. Random effects revealed considerable variation among mothers and years. This study demonstrates that, in long-lived polytocous species, environmental factors may have a greater influence on natal features than previously supposed and the influence from biological factors is also complex. The documented responses to environmental influences provide unique insights into how mammalian seasonal reproductive dynamics may respond to current changes in climate.

Previous research into the liver has mainly examined liver function and liver response to energy restriction. There have been few investigations into how liver mass is coupled to body mass, body condition, age, and reproductive events like lactation. Therefore, we examined the scaling relationship between body mass and liver mass and the influences of age, sex, body condition (back fat), and lactation on liver mass to gain insight into liver-mass variation in white-tailed deer (Odocoileus virginianus (Zimmermann, 1780)). Deer from two sites in Texas (89 males, 70 females) were sampled; one site was sampled before the mating season (premating) and the other site was sampled during the mating season. There was an allometric relationship between body mass and liver mass (scalars 0.59–0.80) at both sites. Also, sex and age were predictors of liver mass at one site, whereas lactation was influential at the other location. Controlling for body mass, males had heavier livers than females during the mating but not the premating season and age was positively related to liver mass. Our findings indicate that sex and lactation status were coupled to liver masses, but the effect of these two factors differed between premating and mating seasons. It appears that animals in situations where metabolic demands might be higher than current nutrient intake, such as mature males during the rut or lactating females, have heavier liver masses when body mass is controlled.

Cohort effects on body mass of deer species are caused by both density-dependent and -independent factors. Cohort effects occur in the year of birth and affect body size throughout life. We hypothesized that deer in low latitudes should be able to overcome cohort effects through compensatory or catch-up growth because mild and wet winter conditions are more amenable for animal growth. We analyzed 27 years of mule deer harvest data from Camp Pendleton, California. Using generalized least-squares regression with restricted maximum likelihood estimation to estimate parameters, we determined that eviscerated body mass of southern mule deer (Odocoileus hemionus fuliginatus) was affected by precipitation and relative abundance. We also found that deer were able to recover from periods of poor nutrition and overcome cohort effects by 2.5 years of age, which has not been demonstrated in other ungulate populations. This study demonstrates that body mass can be used as a tool to assess the nutritional state of a population in an environment with high inter-annual variation in biotic and abiotic factors. Further, managers in environments where mild and wet winters extend growing seasons should consider the possibility that deer may be able to recover from periods of missed growth when making harvest recommendations. Ó 2014 The Wildlife Society.

Beaver management requires understanding beaver habitat preferences. Despite the American beaver (Castor canadensis Kuhl, 1820) being relatively common in the upper Midwest region of the United States, there are no beaver habitat relationship models based on this area. We used 1,735 colonization events from long-term monitoring data generated by the Chequamegon-Nicolet National Forest in northern Wisconsin, USA, to determine what geomorphological and biological factors were selected by beavers colonizing new sites. We developed and evaluated prediction performance for three colonization models: geomorphology factors only, geomorphology and vegetation factors, and a full colonization model based on geomorphology, vegetation, and availability of dispersing beavers. Overall, the geomorphology-vegetation-colonizer model was the best model, predicting actual colony locations better than the other two models. Spatially, the landscape open to beaver colonization was a mosaic of streams with suitable and unsuitable habitat. These models improve our understanding of how beaver site selection factors in the upper Midwest region differ from factors identified in the literature for the western and eastern United States. This information may be useful for land managers in this region seeking to spatially target resources for restoring northern forest landscapes such as the Chequamegon-Nicolet National Forest.

. 2014. Assessing capture success of small mammals due to trap orientation in field-forest edge habitat. Canadian Field-Naturalist 128(2): 191-194.The prediction that trap orientation would not affect the likelihood of capturing small-nonvolant mammals in field-forest edge habitat was tested during late May and early June 2010 at 3 locations in western Tennessee. Traps were placed in pairs along transects in edge habitats with the orientation of one trap facing outward, toward the field, and the other oriented inward, toward the forest. Results reflected no differential capture success due to trap orientation among ages, sexes, species, or locations. This finding should facilitate the inventorying and monitoring of small mammals in an abundant and potentially species-rich habitat type found in many terrestrial regions.