ESTIMATING GOPHER POPULATIONS AND THEIR ABATEMENT IN FOREST PLANTATIONS

Indirect sampling methods for pocket gophers (Family: Geomyidae) lack adequate assessment for accuracy and efficiency. During gopher abateme nt trials in forest clearcuts, our new ''burrow index'' accounted for 95% of the gophers, while the widely used 24 hr open-hole test account ed for only 68%. Using published data, we found that mound counts and plot occupancy provided precise estimates (R(2) = 0.76 - 0.99) of goph er density in clearcuts. We recommend the more efficient ''burrow inde x'' for sampling gophers, and ''effective depopulation'' for estimatin g population change due to abatement, after accounting for natural pop ulation dynamics in ''control'' plots. A modified burrow index on stri p transects can be used for measuring association of gophers with ecol ogical variables.