Tradeoffs between Quality of Offspring and Litter Size: Differences Do Not Persist into Adulthood

Abstract

Persistent effects of the tradeoff between number and size of offspring per litter were examined by comparing mean mass of northern grasshopper mice ( Onychomys leucogaster ) within litters at the end of complete maternal dependence (age 16 days), at separation from mothers (28 days), and as adults (60 days). Although there was a significant effect of litter size on mean mass of offspring early in lactation, young showed compensatory growth as soon as they began eating solid food. No difference in body size was evident at weaning or among adults. Compensatory growth was fueled by increased consumption of food relative to body mass; smaller offspring in large litters consumed as much food per capita as large offspring from small litters. To the extent that body size can influence reproductive potential, the offspring's capacity for compensatory growth suggests that much of the penalty for large litters is through decreased recruitment or through reduced future reproduction by mothers rather than differences in reproductive potential of offspring as adults.