HIGHER REPRODUCTIVE SUCCESS AMONG KIN GROUPS OF BANK VOLES (CLETHRIONOMYS-GLAREOLUS

According to the kin selection theory the degree of genetic relatednes s affects the nature of intraspecific competition and it might promote cooperative and/or altruistic behavior between individuals. We examin ed kinship effects on reproductive success of territorial females and survival of juveniles in the bank voIe Clethrionomys glareolus. Four e xperimental populations were founded in large enclosures (0.5 ha): two consisted of five related (Related, R) and two of five mutually unrel ated females (Unrelated, UR). Each population had five males of hetero geneous origin. Our earlier results showed that populations of the R g rew twice as fast as the UR. Here we show that recruitment and offspri ng survival is connected to spacing behavior of mothers. Unrelated fem ales who had their home ranges close to each other produced significan tly fewer recruits than the related ones. Their home ranges overlapped significantly less and ranges were smaller if they were situated clos e to each other. Furthermore, the survival of juveniles declined with dispersal distance from the natal territory in populations of the UR. Trappabilities of juveniles were also lower among the young whose home ranges were close to unrelated females, indicating avoidance of matur e females. Our results indicate that competition for space is more int ense among unrelated neighbors, decreasing their reproductive success. Infanticide towards unrelated nestlings and/or juveniles is one possi ble mechanism decreasing survival and causing a lower recruitment of y oung. On the contrary, sharing of space among related neighbors did no t seem to cause notable costs on their reproduction. Mature females al lowed related young females to use their territory, but still, the you ng: did not acquire an area for their own reproduction, probably due t o a mother-daughter conflict. The basic social structure of Clethriono mys populations, i.e., exclusive female territoriality, remained the s ame regardless of a high degree of relatedness.