Correlation of Opossum litter size to Maternal Body Condition and Environmental Variation.

            Karan Sharma,   John R. Hisey Lee University

Individual fitness is related to number of offspring produced, which may be influenced by energy balance relating to the mother's body size, intra- and interspecific competition and environmental factors that vary over space and time. We tested hypotheses on these relationships in Didelphis virginiana , a key mesopredator in which litter size is easily assessed, by operating two trapping grids near Memphis, Tennessee over three summers (12,000 trap-nights).   Forty six female opossums were captured with pouch young. Mean number of young per litter was 8.8. No significant relationships were found between number of pouch young per litter and trap grid, year, the mother's mass or length, or predator numbers on a grid and the body condition index of the female.   Wide variation in number of young may indicate, however, that differences in genetics, health, or other factors affecting individual females influenced litter size.