A TEST OF THE SCENT-STATION SURVEY TECHNIQUE FOR BOBCATS

Scent-station surveys have been widely used to monitor bobcat (Felis r ufus) populations, but relationships between bobcat abundance and the index derived from scent-station surveys have not been validated. In a utumn 1988 and 1989 we reintroduced bobcats (n = 31) to Cumberland Isl and, Georgia. We conducted 15 scent-station surveys during September-F ebruary 1988, 1989, and 1990 to obtain scent-station indices (SSI) as we increased bobcat density. We found a positive relationship (r2 = 0. 45, P = 0.0066) between population size and SSI. However, because SSI variance also was correlated positively with SSI, we transformed data to meet the assumption of homoscedasticity for the regression model (r 2 = 0.73, P < 0.001). Predictions of population size using individual scent-station surveys bad poor precision. Analysis of statistical powe r indicated that 4 replicate scent-station surveys had an 80% probabil ity of detecting only large (greater-than-or-equal-to 25%) changes in populations of high density (0.5 bobcats/km2). We recommend that (1) m ultiple scent-station surveys be conducted each year to monitor change s in bobcat populations; (2) SSI values should be calculated as propor tions and transformed to reduce heteroscedasticity; (3) each stratum i n a sampling design should contain as many stations as possible to min imize the problem of discrete data (no. of visits) analyzed as a conti nuous variable (proportion of stations visited); (4) scent stations sh ould be placed as far apart as logistically feasible to minimize multi ple visits by individual bobcats; and (5) results of the power analysi s should be used as a minimum guideline for estimating sample-size req uirements.