| Nest fumigation—the use of volatile plants to control nest-borne ectoparasites—has been studied in birds, but not in mammals. This study was designed to investigate whether the dusky-footed woodrat (Neotoma fuscipes), a nocturnal rodent that constructs large stickhouses, also displays nest fumigation. Four studies were conducted. First, using mark-and-recapture and radio telemetry, stickhouse use patterns were investigated to determine the risk for ectoparasite accumulation. Woodrats in this population are considered at high risk for ectoparasites due to their tendency to reuse stickhouses and remain in the same stickhouse for several weeks. Second, the ectoparasites of those woodrats captured were quantified to ascertain if woodrat's were controlling parasite loads. The majority of rats were uninfested or had only one type of ectoparasite. Fleas (Orchopeas sexdentatus) were the most common type of ectoparasite found. Statistically, more young (subadults and juveniles) than adults were infested with fleas; young rats also had higher numbers of fleas. Third, stickhouses were examined to identify plant species stored in houses and the location of those plants within stickhouses. Fresh sprigs from three evergreen trees were most commonly found: California bay (Umbellularia californica), live oak (Quercus spp.) and toyon (Heteromeles arbutifolia). California bay was statistically more likely to be found near the sleeping nest than in non-nest areas, and was found in equal amounts regardless of whether or not it was the stickhouse base tree. For all three plants, woodrats avoided storing the most mature and chemically potent leaves. Fourth, controlled laboratory experiments were conducted to test repellent effects of California bay, live oak and toyon on adult fleas. Extracts of California bay were statistically as effective as DEFT (a commercially-available repellent) in repelling fleas, whereas, toyon and live oak were not as effective. These results suggest that woodrats decrease the risk for ectoparasite accumulations by placing California bay near their sleeping nest to control their exposure to ectoparasites. Avoidance of the most potent leaves suggests that woodrats may themselves be intolerant of strong phytochemicals. In conclusion, the nest fumigation hypothesis is supported by these studies. |
