Disagreement Among Alaskans About Predator Control Effectiveness

Interesting piece from Alaska Public Media over the weekend that discusses this question: Is predator control working in Alaska? Here’s more from the report, which interviews a state biologist who disputes the the authors of an extensive study about the effectiveness of the state’s plans to control predator populations while conserving other species:

Tom Paragi: What’s fairly common in the boreal region of Alaska, it was something shown in a landmark study that came out in 1992 by department staff, where they reviewed case studies of moose, 35 sites across Alaska and the Yukon, what they found is populations of moose declined to low abundance, which is typically less than about one per square mile, they can stay there and fluctuate a little bit from year to year in areas where the large predators, wolves and bears, remain at their natural densities. And what they found in some of those case studies is that where predators had been reduced through harvest or predator control, that allowed those moose populations to increase in abundance to more than one moose per square mile. And they would remain there. Once predator control stopped, they would remain there for a period of time. But over time, as the predators fell back into the area, increased to their prior abundance, and especially if you have done things like a severe winter that can, in turn cause a decline back down.

Casey Grove: I just want to be really clear, I mean, one thing that those researchers had said was that the state doesn’t have the scientific framework to back up the notion that predator control does work as intended. And it sounds like you’re saying that’s not true, that the state does have the scientific framework to back that up. Is that accurate?

TP: Yeah, the intensive management law came about in 1994. And at that point, there had been a couple decades of research in Interior, in Southcentral Alaska, that had looked at the effects of wolf and bear predation on moose and caribou populations. And they found that there are circumstances where, when prey populations get to some lower levels, predation can can hold them at those levels. And in terms of Unit 13, another thing that I looked at was, there were four sub units that had wolf control in them, and those are the ones that are driving this trend you saw on Unit 13, where the population was declining and harvest declined until the early 2000s, and after wolf control, they increased.

Here’s some tidbits from the study, made by longtime state biologist Sterling Miller, the lead author, and co-authors David Person and Terry Bowyer:

We analyzed harvest data to test hypotheses that nearly 4 decades of effort to reduce abundance of brown bears (Ursus arctos), black bears (U. americanus) and gray wolves (Canis lupus) in an 60,542 km2 area in south-central Alaska (Game Management Unit [GMU] 13) was positively correlated with moose (Alces alces) harvests in some time-lagged fashion. Predator-reduction efforts were progressively more aggressive over decades (both de facto and officially designated predator control) and did not have clear starting points which complicated our post hoc analyses. We documented no positive correlations (p > 0.05) between harvests of brown and black bears and subsequent moose harvests for any time lag. Moose harvest was negatively correlated with the previous years’ wolf harvest, but the relationship was weak (correlation = ?0.33, p < 0.05). Consequently, we reject our hypotheses that harvest of predators was positively correlated with moose harvests. We also observed no differences in mean moose harvests during periods of officially designated wolf control (2005–2020) and a previous period (p > 0.50). We recommend that predator reductions designed to improve hunter harvests of moose be conducted within a research framework that will permit improved interpretations of results and the implementation of an adaptive-management approach to achieve management objectives.