Dusky-footed woodrat (Neotoma fuscipes) abundance is often estimated using house counts; a house typically being described as a large pile of sticks, usually built on the ground, but occasionally on tree limbs. For purposes of the count, it is sometimes assumed that each "active" house represents one woodrat. An active woodrat house is indicated by its appearance; fresh vegetative cuttings at the house and the presence of recently deposited fecal pellets. Results from our ongoing study in the foothills of the Sierra Nevada suggest that, in some habitats, house counts may not be a reliable method for estimating dusky-footed woodrat population size. Woodrats frequently resided in atypical houses, which bore little resemblance to typical houses and were often very difficult to locate, if not altogether overlooked. These included houses within tree cavities, rock crevices, and ground holes. Furthermore, individual woodrats often used and maintained more than one house and, occasionally, more than one woodrat occupied or used a single house. The classical use of total house counts for population estimation of dusky-footed woodrats could potentially cause substantial errors in estimating population size.
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