SOCIAL-STRUCTURE OF THE MOUND-BUILDING MOUSE MUS SPICILEGUS REVEALED BY GENETIC-ANALYSIS WITH MICROSATELLITES

The Mound-building mouse Mus spicilegus possesses a unique behaviour a mongst mice. It constructs large earthen mounds and associated nesting chambers which serve to store food for immature individuals during th e winter nesting period. We have used genetic analysis of four autosom al and four X-linked microsatellite loci to determine relationships be tween individuals inhabiting 40 mounds in Bulgaria. We show that, in a lmost all cases, individuals in a mound are the product of multiple pa rentage. We estimate the minimum number of males and female parents co ntributing offspring to each mound and demonstrate that at least two m ale and two female parents contribute offspring to a minimum of seven mounds. Analyses of relatedness coefficients and allele sharing values demonstrate that parents of different sibships within mounds are more related than if they had been chosen at random from the population an d suggest that it is the female parents that contribute this excess re latedness. These results suggest that the mechanism by which individua ls congregate to build mounds is kin-based and that the evolution of m ound building and communal nesting in M. spicilegus is due in part to kin selection. This study represents a novel approach to the study of mammalian behavioural ecology. We have used a genetic dataset to const ruct an outline of social structure in the absence of behavioural data . These inferences can now be used to direct further work on this spec ies.