Effects of sex and breeding status on habitat selection by feral House mice (Mus musculus) on a small Mediterranean island

Patterns of habitat use of the house mouse (Mus musculus) in relation to se x and breeding status were studied in April and May (the early breeding sea son) in two structurally different habitats on a small Mediterranean island in NE Spain. Overall mice abundance increased from bare and rocky areas to areas with a dense cover of shrubs and herbaceous plant. Females were asso ciated to shrub areas in April. shifting towards more herbaceous areas in M ay. Males were less selective, being only slightly related to shrub height in April, and they were not associated with structural habitat features in May. Overlap in habitat use by sexes existed in both months being more redu ced in April than in May. Female densities were significantly higher in the habitat with dense vegeta tion cover (suitable habitat) than in the habitat with scarce vegetation in both months, while densities of males were not. Male density decreased fro m April to May in the suitable habitat, and intersexual competition was exc lusively detected in the period of higher male density in this habitat, int raspecific competition explained the spatial distribution of sexes regardle ss of habitat structure characteristics In absence of competition the spati al distribution of sexes was mainly related to habitat structure. Females and males started sexual activity early in the season in the suitab le habitat. Weight of females was higher in suitable habitat in both months , also showing a positive association with the herbaceous cover, and the av erage weights of males and females at trapping stations were positively ass ociated. Our results are finally discussed in relation to the social organisation mo dels proposed for house mouse populations.