I do not know all of the details of the projection model that Montana FWP has used to project the effects of human offtake on wolf dynamics, so I am not completely certain why it projects a small effect of harvest in comparison to the regression of past population growth rates on observed offtake rates.

However, from descriptions of the model that have been released, I think that one logical explanation is that the model only incorporates the direct effects of offtake. That is, it appears that the projection model assumes that the effect of human predation is completely accounted for by subtracting out the number of wolves that are shot. This approach implicitly assumes that human predation will not alter other demographic processes. In formal terms, it appears that the projection model implicitly assumes that covariances among demographic parameters used in the projection are all equal to zero.

However, a great deal of recent literature in ecology shows that the effects of a predator on its prey (in this case, the effects of people on wolves) includes two components: direct offtake and the 'nonconsumptive component' or 'risk effects'. Recent work with a wide variety of taxa, both experimental and observational, has shown that these risk effects can comprise a large proportion of the effect of a predator on the dynamics of its prey. For example, recent research on wolves (Brainerd et al. 2008, J Wildl Manage 72:89-98) has shown appreciable effects of breeder loss of the stability of wolf packs and the probability of breeding in the subsequent year (as discussed in our paper). In formal terms this is evidence that covariance among the demographic processes should be incorporated into a projection model of harvest effects.

When one regresses the observed change in population size on the proportion harvested (as in our paper), the change in population size includes both direct and nonconsumptive effects.

We have suggested for several years that analysis of large mammal dynamics and analysis related to management and conservation must start to address the nonconsumptive effects of predation and harvest (see Creel & Christianson 2008. Relationships between direct predation and risk effects. Trends in Ecology & Evolution 23: 194-201.) Contrary to Dr. Ream's assertion that Jay Rotella and I behaved irresponsibly by failing to bring this point to the attention of Montana FWP, this has been the central point of many recent publications in recent years, and I have discussed it directly with Montana FWP personnel on many occasions.