Estimating population size in the banner-tailed kangaroo rat

Mark-recapture population estimates from censuses of banner-tailed kangaroo rats (Dipodomys spectabilis) at two study sites in southeastern Arizona were compared to results of direct enumeration. We wished to assess the validity of direct enumeration for this species, and to compare the ease of use and concordance of this approach to determining population sim with various closed-population estimators from program CAPTURE. Probabilities of capture of kangaroo rats were high at both study sires. Estimates based on trapping at mounds were all highly correlated with direct enumeration estimates after 3 nights of trapping. Adding a fourth night's trapping changed population estimates little for adults, but increased the estimated number of juveniles. In contrast, estimates based on a trapping grid substantially underestimated the number of animals known to be alive, suggesting that trapping on a grid is an inefficient means of assessing population size for these rodents. Saturation trapping around inhabited mounds is the preferred method for this species, and direct enumeration, a 2-night Lincoln-Petersen index, or even a quick count of active mounds provide precise indices of population size.