Estimating Densities of Peromyscus leucopus Using Live-Trap and Nestbox Censuses

We determined if various trap and nestbox census methods used during a 22-year monthly study yielded consistent density estimates of the white-footed mouse ( Peromyscus leucopus ) in an Ohio woodlot. Because trap and nestbox census methods were used concurrently for only 32 months during the 22-year study, we also compared census methods that had been used sequentially by first removing seasonality using density-dependent parameters. Nestbox estimates were lower than trap estimates in summer and higher in winter, and the three variations in trap census methods used over 22 years did not result in different density estimates. Twenty-five percent of individuals caught in nestboxes were never caught in traps, and nestboxes increased densities by 7% by increasing nest-sites during the 15 years they remained in the woodlot. Because the ‘minimum number alive’ estimator could not overestimate the population in an isolated woodlot, trap censuses underestimated the population in winter, and nestbox censuses accurately estimated the population in late autumn and winter.