Use of California bay foliage by wood rats for possible fumigation of nest-borne ectoparasites

Studies were conducted to test the hypothesis that dusky-footed wood rats (Neotoma fuscipes) place bay leaves (Umbellularia californica) on or near the sleeping nest in their stickhouses, with the result that the leaves act as a fumigant against nest-borne ectoparasites. Although many stickhouses were found to contain bay, oak, and toyon leaves, only bay was found significantly more often near the nest than away from the nest. Bay leaves were nibbled in a fashion consistent with the release of fumigating volatiles. Oak leaves, a known food staple, were nibbled in a fashion more consistent with eating. Analysis of the density of ectoparasites in samples of sleeping nest material showed few parasites in most nests, but heavy infestations in a few nests revealed the potential for large numbers of nest-borne ectoparasites. Samples of 1 g of whole and torn leaves of bay, toyon, and oak were incubated with flea larvae in mason jars for 72 h. Torn leaves (to simulate nibbling effects) of bay significantly reduced larval survival to 26% compared to 87-94% survival of larvae incubated with torn oak and toyon leaves. These findings provide evidence that dusky-footed wood rats place bay foliage around the sleeping nest with the effect of reducing their exposure to nest-borne ectoparasites. Copyright 2002.