Maternal care and reproductive state-dependent mobility determine natal dispersal in a wolf spider

By facilitating avoidance of kin competition and inbreeding, natal dispersal can have direct fitness consequences. Mechanisms that optimize indirect fitness may be equally important. When relatives compete for the same resources (kin competition), evolution of elevated dispersal rates can be favoured, so that most resource competition is among nonrelatives. When offspring are incapable of dispersing, maternal behaviour may influence natal dispersal in a positive way, by spreading offspring throughout the habitat. By combining laboratory and field observations, we studied dismounting behaviour of spiderlings from the maternal abdomen (i.e. maternal care) and mobility patterns of female wolf spiders, Pardosa monticola. Laboratory observations on the duration of maternal care indicated that spiderlings desert the maternal abdomen gradually within 185 h of hatching. Detailed behavioural monitoring within the spider's habitat showed that females carrying spiderlings on their back were more mobile with greater directionality of movement than females of other reproductive states. This alteration in female mobility, together with the gradual dismounting of offspring from the abdomen, indicates maternally induced natal 'hitchhiking' dispersal. These findings show that maternal effects may influence natal dispersal not only through condition dependence, but also by the active spreading of offspring throughout the habitat before they actively (decide to) disperse. This gradual dismounting of offspring is evolutionarily beneficial for the avoidance of kin competition. (C) 2007 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.