Effects of supplemental food on the social organization of Mongolian gerbils during the breeding season

Abstract

AbstractSocial groups occur in many rodents and vary in size and complexity under varying environments. Food availability is often limited in northern temperate regions and alters the life history and behavior of rodents. Increased food availability is hypothesized to increase the size and complexity of rodent social groups by enhancing individual survival and philopatry. We tested this hypothesis in Mongolian gerbilsMeriones unguiculatusunder semi‐natural conditions in Inner Mongolia, China. The Mongolian gerbil is a cooperative breeder living in groups year‐round. Gerbil colonies in 10 m × 10 m chambers were the experimental units, with four replicate chambers each for food supplementation and food unsupplemented controls in 2004 and six replicate chambers for each treatment in 2005. At 2‐day intervals wheat grain supplemented the normal food in experimental chambers throughout the breeding season (May through August). We estimated founder mortality, cumulative recruitment, proportion of philopatric juveniles, ages at sexual maturity and social group size in each colony from May through August. Rates of change in group size were inversely related to social group size. The social organization of Mongolian gerbils did not differ in any of the measured parameters between food‐supplemented and ‐unsupplemented chambers. Therefore, additional food does not influence the social organization of Mongolian gerbils during the breeding season.