Ectoparasites and sett use in European badgers

The European badger,Meles meles, constructs burrows (‘setts’) of various sizes and types, some of which are very large and complex. The hypothesis that large setts allow badgers to move regularly from one nest chamber to another, thereby avoiding accumulation of ectoparasites, was tested. The ectoparasite load of 32 wild badgers was measured and the daytime sleeping locations of 33 radiocollared individuals, 16 of which were treated with anti-parasite spray, recorded. Untreated badgers were infested with fleas, ticks and lice, and they regularly shifted from one sleeping site to another within a sett, rarely spending more than 2 or 3 consecutive days at the same site. Anti-parasite treatment decreased the frequency with which badgers switched to different nest sites. Badgers did not choose sleeping sites at random when returning to the sett each morning: they tended to return more often than would be expected by chance to a site that they had occupied the previous day, and less often than expected to a site that had been vacated by another member of the group on the preceding night. Badgers may thus remain in the same nest until perceived ectoparasite challenge exceeds a certain threshold and avoid nests recently vacated by a conspecific because the level of infestation of such nests is also likely to exceed the threshold. Use of multiple nests as a defence against ectoparasites may be a common trait in burrowing mammals.