Estimating low-density snowshoe hare populations using fecal pellet counts

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Snowshoe hare (Lepus americanus) populations found at high densities can be estimated using fecal pellet densities on rectangular plots, but this method has yet to be evaluated for low-density populations. We further tested the use of fecal pellet plots for estimating hare populations by correlating pellet densities with estimated hare numbers on 12 intensive study areas in Idaho; pellet counts from extensive transects (n = 615) across northern Idaho enabled rectangular plots (0.155 m2) to be compared with paired small (0.155 m2) and large (1 m2) circular plots (metre-circle plots). Metre-circle plots had higher pellet prevalence, lower sample variance, and lower estimates of pellet density than the other plot types. Transects comprising circular plots required less establishment time, and observer training reduced the pellet-count bias attributable to plot shape. The number of hares occupying intensive study sites was correlated with pellet density on all plot types, but rectangular plots provided a slightly closer linear fit to hare numbers than did metre-circle plots. The relationship between pellet density and hare number may have been curvilinear rather than linear, but linear and nonlinear models provided similar numerical estimates over much of the range of pellet densities. These results indicate that pellet counts are a robust estimator of hare numbers in low-density populations, and that metre-circle plots represent an improvement over standard rectangular plots in terms of unbiased pellet counts, sacrificing little predictive power. We recommend using pellet counts in metre-circle plots for estimating populations of snowshoe hares in their southern distribution.