Power analysis of wolf-moose functional responses

Gray wolf (Canis lupus) predation is density dependent if the proportion of prey killed by wolves increases with prey density. The functional response is 1 component of wolf predation that has an important effect on whether d ensity-dependent predation occurs, and consequently whether wolves have the potential to regulate prey to a low-density equilibrium. Because the funct ional response alone may determine if predation is regulatory, researchers have been attempting to accurately describe the functional response for wol ves. We used simulated datasets based on the typical variances found in wol f-moose (Alces alces) predation data to evaluate the sample size required t o distinguish between 2 common forms of wolf functional response: Type II a nd Type III. We found that we required sample sizes considerably larger tha n those likely attainable for wolf-moose predation studies. This conclusion was true even for a strongly sigmoid functional response (C > 2 in the Mic haelis-Menton equation). Our analysis suggests it would be better to devote more effort toward measuring total predation losses versus trying to deter mine the shape of the functional response.