Development of a Distance Method for Deer Census from Pellet Groups

Abstract

Estimates of deer pellet groups on 0.0001-, 0.0005-, 0.001-, and 0.01-acre plots declined from about 5,000/acre on the smallest plots to 1,000/acre on the largest plots. The relationship conforms to a log polynomial curve which is closely approximated by the hyperbola d = a' s-' (d = density, s = plot area, a and b = regression constants specific to an area). This pattern typically arises from counts in bounded plots because a pellet or other small part of a group is more likely to occur alone and be recorded as a group on small plots, whereas, when large plots are used, it is more likely that groups will be correctly defined or that clusters of groups will be described as a single group. The effect is most pronounced where rain, sparse ground cover, or steep slopes cause groups of pellets to become widely scattered. A distance method has been developed and tested for estimating pellet group density, and its application to census of a small population of red deer (Cervus elaphus) is discussed. The census model used requires estimates of pellet group density, disappearance (decay) rate, and defecation rate.