FACTORS ASSOCIATED WITH RACCOON MORTALITY IN IOWA

Biologists need to better understand the effects of harvest on the population dynamics of furbearers. Thus, we used telemetry and Cox's proportional hazards statistics to investigate how habitat factors and harvest regimes were associated with mortality patterns of raccoons (Procyon lotor) in Iowa during 1983-89. Among birth-year (BY) raccoons, greater harvest levels (as estimated by direct recovery rate of ear-tagged animals) were associated with increased hazard, or mortality rate. We found no difference in annual survival among animals greater-than-or-equal-to 1 year old (after-birth-year, ABY), and changes in hazard rate of ABY raccoons were not associated with greater harvest levels. The relative proportion of animals harvested by hunting and trapping was marginally associated (P = 0.10) with harvest mortality of BY raccoons, but not with mortality of ABY raccoons. As mortality due to harvest of BY raccoons increased, more equal proportions were taken by hunting and trapping. Survival of ABY females (S(f) = 0.58) was greater (P = 0.03) than that of ABY males (S(m) = 0.37), but there were no differences related to sex among BY raccoons. Habitat use and body condition were not associated with hazard rates, Known behavior patterns and more frequent movements of BY and male ABY raccoons may be related to greater vulnerability to harvest relative to ABY females. These analyses directly link harvest level and relative importance of trapping and hunting to mortality rates of sex and age classes in the population. Our results emphasize that change in the dynamics of the BY age class is a major factor affecting demographics and harvest management of raccoons. As harvest levels increase, proportionally more BY raccoons will die compared with the ABY age classes, and deaths by hunting and trapping will become more equal in importance.