Thursday, 24 June 2010

Moose management - it works, sometimes

ResearchBlogging.orgWell, I finished reading "Science and Values Influencing Predator Control for Alaska Moose." It was actually a very good read, with excellent cadence, even if I had heard all of this at conferences before. I've got a few general comments on this, but first I'll lay out the review a bit.

It comes in four five.
First, it reviews the relative effects of predation to other factors for moose. After all, if it's mostly nutrition limiting moose, additional rounds of predator control will not bolster moose populations, or will only do so slightly. Their arguments are old-hat to anyone who's been on this ride for a while, but it's worth repeating:
  • Most moose in AK are at low density.
  • Moose at low density are primarily limited by predation.
  • Moose in some areas experience effects from high density.
  • Moose in high density areas are not very effected by predation.
  • Everyone is effected by random "bad winters" (Winterkill).
  • Most moose predation mortality is in juvenile moose.
The second section dealt with manipulative studies - that is to say, our previous experience with Intensive Management. Here there's eight cases laid out that I won't go into exhaustive detail on. The best evidence, by far, is GMU 20A, or the moose south of the Tanana river and north of the Alaska Range. McGrath has potential to be a more important finding, but as of yet it is a weak-moderate finding. I am very unconvinced by data from 20D, but others might consider the data from that unit good. In general, the pattern of predator manipulation (which wasn't always IM) was followed by improved moose censuses. Some of these have thus-far been sustained (20A), others less so (Kenai).

The third, and shortest section, is on sustainability of the increases moose counts. This is the shortest section, since the data is the newest (or in other cases, the weakest). Again, the best data comes from Unit 20A, where there's been a sort of accidental experiment going for a while now. Important factors in the long term-sustainability of these populations seems to be a) carefully monitoring nutritional status b) doing habitat improvement when possible (this includes allowing burns to proceed, or doing controlled burns) c) allowing larger cow moose hunts to keep the population short of carrying capacity (overshooting K is a Bad Thing™).

Next comes the sustainability of wolf and bear populations in interior AK. The evidence for sustainability is very firm, and although I'm sure some people could twist it, in general most people can recognize that the situation is fine. The areas involved are vast, getting people involved in bear harvest is actually very hard, wolves and wolves do an exceptionally good job compensating for high harvest, and IM areas only seem large until you consider how big the state is, and how many and how large non-IM areas are. This is the section from my earlier quote. 

Lastly, there are some general comments on the sociology and public opinions around IM. It discusses logical fallacies employed by both people for and against it, and seems to suggest reconciliation is unlikely because either user group starts with fundamentally different premises and values. I think this is an overly grim view of the situation, and have hope that open communication can bring the public to some sort of consensus. This section had  a great table which I'll repost here.

In general, the message is that "Intensive Management Works*" Where there's a footnote that would read "*Under some models, in some conditions, some of the time." Which I think most biologists would be willing to concede. A large part of the problem over IM is the perception of conflicting values, which is an inherently non-scientific issue. I know that some Scientists would reply that the HD equilibrium is inherently unstable, and it's the LD "dynamic" equilibrium that's the most stable state. I'm not sure there is good ways to argue for or against that right now, without, say, 20 more years of data that doesn't exist.

Okay, here's my thoughts, in no particular order:
Caribou are generally a less-reliable prey than moose because seasonal distribution is more clumped and unpredictable, and voids exist in caribou distribution in inland Alaska.
I agree with the latter part of the sentence, but the former really needs a citation. I can't just let that pass. Where caribou are abundant, they have the potential to be a substantial part of wolf diets, potentially lowering the number of moose. I can illustrate this with a model, but I don't have data to back this up. However, neither do they.

It seems like Winterkill is often ignored as a major factor moose population trajectories. And it's hard to react to stochastic severe winter events fast enough to change management. This is the biggest lesson I take from the Fairbanks winter of 1971 (though I take others as well). We need a better manner of accommodating severe winter events.

Given the invasion of White Tailed and Mule Deer from the Deep South™, should our management objectives change from managing for high density populations to managing for low density? LD populations have two big advantages - first, contact between moose is lower, so disease transmission is reduced. Second, moose are in better nutritional status, which correlates strongly with the ability to mount immune responses to the emerging diseases. On the other hand, LD moose populations have declining recruitment as population declines due to diseases, whereas in HD moose populations, recruitment increases.  I don't know the answer to this question. Science is needed, because CWD and Winter Tick are coming to AK whether we like it or not.

IM for bears could probably be highly refined. Bears are even more cultural than wolves are, and in one instance less than 50% of killed 72% of calves. You could probably get away with just removing, or killing, the better predators. I think we need to start viewing bears as people long-ago did - as human in their cognition. But I'm a big proponent of the idea that bears show strong cultural evolution, so take that with a grain of salt.

Boertje, R., Keech, M., & Paragi, T. (2010). Science and Values Influencing Predator Control for Alaska Moose Management Journal of Wildlife Management, 74 (5), 917-928 DOI: 10.2193/2009-261

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