Eric A. Rickart

Elevational zonation of mammals in the central Philippines

Trapping and netting of small mammals on a land-bridge island (Leyte) and on an oceanic island (Negros) revealed similar patterns of elevational change in abundance and species richness. Fruit bats (Pteropodidae) reached their greatest local densities in agricultural areas, and were least abundant in montane mossy forest. The fruit bats found to be common in agri- cultural areas are widespread in Southeast Asia: in contrast, species that were most common in forested areas are Philippine endemics. Fruit bat abundance was greater on the oceanic island than on the land-bridge island. Trappable small mammals (families Soricidae and Muridae) showed no change in species richness with increasing elevation, but did show a gradual increase in overall abundance. Even though the oceanic island was depauperate of non-volant mammal species, it had the higher abundance of non-volant mammal individuals; however, this may have been due primarily to differences associated with the elevation of sampling sites. Murid rodents at the higher elevations on Leyte tend to be those that are members of the old endemic group of Philippine murids, and those at lower elevations tend to be members of more recently arrived groups. Most non-volant small mammals at all elevations on the oceanic Negros, and in agri- cultural areas on Leyte, are non-native species.

Impact of livestock grazing on plant and small mammal communities in the Ruby Mountains, northeastern Nevada

Abstract. We assessed the effects of livestock grazing on vegetation and small mammals in semiarid habitat at a site in northeastern Nevada. Habitat within a fenced exclosure that had been protected from grazing for more than 50 years supported more vegetation and had greater plant diversity compared to habitat immediately outside the exclosure. Likewise, species richness and abundance of small mammals were greater in ungrazed areas. Results suggest that grazing regulation in recent decades may account for some of the changes seen in regional plants and small mammals over the past century. The incorporation of long-term exclosures in a comparative framework permits differentiation of the direct effects of grazing on biotic communities and thus provides a reference point for assessing the influence of grazing relative to other factors in the interpretation of historical change.

Serum thyroxine and seasonal fattening of free-living piute ground squirrels, Spermophilus mollis (Rodentia: Sciuridae)

Serum thyroxine and body composition of free-living Piute ground squirrels were examined during the season of above-ground activity. Serum thyroxine titers were 2-10 times higher than those reported in laboratory studies on other species. Among juveniles, both body size and lipid content were negatively correlated with thyroxine, whereas these variables were not significantly correlated among adults. Significant sex differences in serum thyroxine were observed for both age groups. Results suggest that the seasonal cycle of body weight is driven by an underlying metabolic cycle but that individual fattening schedules are determined by environmental conditions.