Isle Royal Lessons: Predation Risk v. Dinner

It's been a while since I've written a science blog post, and not because I haven't been reading papers. On the contrary, I've had the exact opposite problem! I'd like to revisit some work done on moose on Isle Royal, Michigan, one of the best studied ecosystems in the US. Reading about the Isle Royal studies was part of what got me into biology to begin with.

Isle Royal is an island in Lake Superior, north of the tip of the Upper peninsula, and not far from the coast of Canada. It's around 70x15 km in size, and almost all of it is encompassed in Isle Royale National Park. The island is the result of geologic tilting, which results in long ridges and islets that all run in the same north-east sort of direction. It's a wonderfully beautiful area,  and the site of much study between wolves and moose. There used to be caribou there as well, but they were expatriated. I would love to see them reintroduced there, but I'm a tad biased towards Caribou, aren't I?

Joan Edwards, now at Williams Collage, did regular surveys of the location of moose sightings. They patrolled moose trails, and did coastal surveys using a boat, and recording whether it was a bull, cow, whether it was alone, whether it had a calf, and so forth. Additionally, she surveyed the diet through observation, recording bouts greater than 10 minutes.

What she'd found is that there were quite the change in locations between cows with calves and all other moose. Bulls and cows without calves tended  towards the ridges on the main island for the beginning of the growing season, before meandering their way towards the shoreline and the aforementioned small islets in July-Sept. This is to contrast with cows with calves, whom were very strongly associated with shoreline, or islets, from May through the remainder of the season. Moreover, they showed that the cows with calves had a very poor quality diet when compared to those without. I've reproduced a figure showing their distribution in various seasons, and you can really see that the cows with calves really had a strong association with those non-interior sites.

Now cow moose have a large investment in calves. It's not the pregnancy so much, but the lactation afterwards that really kicks them in their behinds. Whereas a male's fitness tends to come from its ability to cover multiple females, a females fitness comes from its ability to successfully bring the offspring to independence. Thus, a male is limited by its ability to snarf down forage and become large enough to be dominant, and a female is limited by her ability to trade off predation risk and her basic needs in terms of body condition. Additionally, you could infer that the variance in reproductive success in bulls (either they have a ton of success, or very very little) would lead them to very different risk-benefit calculations as to whether they want to eat in food-rich but predator heavy areas. 

Put into this context, Joan Edwards' research makes quite a bit of sense. Each class appears to be trying to maximize their fitness. She throws out Calves are likely to imitate their mothers as an alternate explanation, but I think she's right to dismiss this alternative fairly easily, since they could just as easily find the same assemblage of forage elsewhere, and at greater quantities. Addationally, I haven't seen the behavioural patterning work go very far with moose, and it's quite possible that that hypothesis petered out in the intervening decades.

However, I do have some general criticisms. First, the study is dependant on sightings, but I saw no estimation of sightability. Supposedly the long duration of observation could rectify that, but in such a dense, closed forest, opportunities for missing animals are rife. Secondly, the sightings could have been systematically biased by one of two ways. First, the lowest predation risk areas for cows with calves on the mainland could have been the hardest to get to, due to terrain, vegetation cover, and other factors. Human bias in these studies can be sizeable, as no one likes to hang around in a hard to reach boggy area looking for moose. Secondly, the mere act of moving about could have scared the cows with calves off in the mainland, because of their heightened concern as to predators. Really, the way to do this sort of study the best would be through radio telemetry, aka collaring and fallering. All that said, I think the effect is generally a real one, albeit not as strong as Dr Edwards suggests.

Edwards, J. (1983). Diet shifts in moose due to predator avoidance Oecologia, 60 (2), 185-189 DOI: 10.1007/BF00379520

Sentences worth pondering

Currently, the primary practical factors ensuring that Alaska predator populations remain sustainable include 1) lack of tradition and interest in harvesting wolves and bears relative to harvesting moose or caribou, and 2) the greater challenge and cost associated with harvesting wolves and bears because predators are elusive, particularly in forested areas, and usually occur at low densities compared with moose or caribou. A substantial, long-term change in ≥1 of these factors will warrant a reexamination of whether sustainability of predator populations is adequately ensured.

This from Science and Values Influencing Predator Control for Alaska Moose Management in the new issue of JWM.

Prodigious Pronghorn Population Projections

Can the presence of wolves be good for prey species? Intuition seems to suggest the answer is no. After all, wolves eat prey, and being eaten is fairly bad for one's health. Wolves are implicated in a number of natural declines of prey species in a number of systems, especially in closed populations where immigration can't bolster floundering populations. The use of wolf control is a controversial tool which I won't discuss at great length here, but one of the key assumptions is that it increases survival of some age classes of prey.  Before I go much further, I've added some entries to my glossary over to the right, for ecological terms.

One of the most vulnerable age classes are neonatal animals and juveniles, or the year's young. While surviving to second or third year doesn't guarantee you'll survive to old age, if you're a deer, it does mean you're fairly less likely to die. Adults are very good at surviving, since evolution has shaped them to be surviving machines, capable of hyper-vigilance, amazing running speeds, and so on. The young, however, enjoy much less of that sort of protection. There tends to be lower survival for the young of the year, and this can be a major factor governing population fate - if you die young, it's hard to do much breeding.

Re-colonizing wolves provide a wonderful mini-experiment to see what the effects of their presence or absence is on various age groups. Kim Berger and Mary Conner, both at Utah State University at the time, studied the effects of re-colonization on pronghorn neonatal survival. Berger and Conner selected two study sites with wolves, and one that was free of wolves in Wyoming. Coyotes were much less abundant at the sites with wolves than they were at the sites with wolves, as they had demonstrated in a previous study.

Fawns were located through a good old fashion leg-work (they must have good vehicle access out there!), and through watching gravid females until they dropped their fawns. They would capture the neonates, weigh them, age them, record the sex, and assess over-all health in a few categories before fitting them with a breakaway radio collar with a mortality sensor. When the animal dies, the radio signal from the collar changes, allowing the researches to swoop in and look for cause of death. Some things they would look for include

1. whether the fawn was alive at the time of the attack
2. tracks, scat, hair, and any caches that might help them identify the predator
3. signs of starvation or other accidents.

The sort of predator who killed it could be classified based off of previously described characteristics. One thing I've always wondered is if there is a better way to ID the cause of death more adequately. However, kill site characteristics have been frequently used before, and will suffice for here.

Ignoring the factors of survival for a moment, there was much greater fawn mortality among wolf free sites than wolf abundant, with as low as 0% survival in one year. The overwhelming majority of the mortality came from either demonstrable coyote predation, or likely coyote predation in those wolf free sites. Coyote predation was still a major factor in wolf abundant sites, but over-all survival was much higher in all years, with the lowest being 24%, higher than the highest survival in any year in the wolf free site. Thus, the presence of wolves appears to beneficially change the survival rate of pronghorn calves through reducing coyote mortality.  Modelling this forward using other vital rates for pronghorn, they find that the wolf-free sites will gradually suffer total collapse, while the wolf abundant sites are quite stable. Clearly, our earlier intuition was not entirely correct about the effects of having wolves in these populations.

This fits nicely into a framework that I've previously mentioned, which is the "Meso-predator release hypothesis." The idea is that wolves or other apex predators (bears, cougars, etc.) keep middling scavenger-predators (such as fox, coyote, racoon, skunk) suppressed when they're around and healthy. They can suppress them through feeding on common prey, attacking meso-predators directly, and so on. This is a top-down effect, where high trophic levels (animals that do bulk of the eating other things) influence the composition of the lower trophic levels (prey; the things that are eaten).

Within the state of Alaska, it begs the question whether there are significant numbers of meso-predators, and whether they are similarly released in times of intensive management. A entirely separate and important question is whether this release negatively impacts prey populations. To my knowledge, no one has done any sort of extensive study of meso-predators in the state. Our knowledge of background fox and coyote density is not very good, and after asking several people, I begin to suspect there are no density estimates for regions of the state. Given that, I am sure no one has looked at meso-predator densities during periods of IM. Anyone who knows otherwise is encouraged to email me! However, the latter most question is probably best identified - there have been studies of calf mortality after bouts of IM, and I don't anyone's identified a shift in mortality towards meso-predation.

---

Berger KM, & Conner MM (2008). Recolonizing wolves and mesopredator suppression of coyotes: impacts on pronghorn population dynamics. Ecological applications : a publication of the Ecological Society of America, 18 (3), 599-612 PMID: 18488620

Things that have been on my mind a lot: Mesopreadators.

One thing I have been thinking a lot about is Mesopredators. Mesopredators are medium predators, such as racoons, coyotes, snakes, etc etc. A bear, wolf, puma etc would be a top predator, and not a mesopredator.

See, I was reading a paper recently about Pronghorn in Wyoming, where they had wolf-free and wolf-abundant sites. In their wolf-free sites, fawn (pronghorn have fawns, for some reason) survival was near 0 in some years, whereas in nearby wolf-abundant sites, fawn mortality was very low. They argue that the difference was in mesopredators, who differentially prey on fawns, and they try to show that coyote predation makes up the bulk of the wolf-free mortality. I know how practically difficult it is to make these calls, so I remain dubious of that. Still, it's hard to argue with that kind of finding in survival.

So, does interior AK have mesopreadators of consequence for our game? Coyotes are definitely mesopredators, and wolves generally do a good job keeping their populations surprised in most of the state (Coyotes are recent arrivals). I don't see much of a release when wolves are removed. Perhaps there are other factors limiting coyote release. Lynx can prey on reindeer calves, but do wolves keep lynx suppressed? I have a hard time envisioning this, because they don't have much niche overlap outside of that.

I'm still thinking about this, but I'm not sure mesopredators are a major factor in large game dynamics in non-SE Alaska.

Predator Control by Press Release

If I was doing science by press release* to try and convince people everything was great about Predator Control, I don't think I would have taken the tack used in the AP story that the News Miner and the ADN picked up. This story is rife with problems.

First, while it's true that the current program really got started by Murkowski, there has been active predator control of one sort or another since pre-statehood. Poison, bounties and aerial shooting was employed by government agent until statehood. Aerial shooting continued with the public until 1972, when the federal Airborne Hunting Act was passed. This coincided with several harsh winters in the state, resulting in heavy predator depression of game populations.

In 1975, the first wolf control was authorized in game management unit 20A, which is south of the Tanana river from Fairbanks. This was conducted by only ADF&G staff. The policies were shaped over time through the 80s, and in 1992, the Board of Game (BOG) added control to three areas. Due to massive backlash from tourists, Hickel reconsider and BOG revoked their plan. In 1993, BOG authorizes additional predator control for 20A. Predator controlled continued until Knowles became Governor, and suspended all programs.

Because of the long history, I don't think it's fair to say Murkowski is responsible for predator control. It would be like saying I started the tradition of having breakfast this morning. Sure, it's technically true, because there was a gap of about 24 hours where I had no breakfast tradition, but it ignores all the breakfast I've had other days.

My next big complaint about the story has to do with mis-leading verbiage. The story implies that of all areas of predator control, a few have been successful. It then cites McGrath, and the Southern Alaska Peninsula. If we're allowed to talk about predator control as a holistic idea, a better example would be the aforementioned GMU 20A. The area currently hosts some of the largest populations of moose in the state, and very healthy populations of wolves (though not the healthiest, due to the 2003 invasion of a depeliating parasite).

If we're only talking about current areas, then I have some complaints. First, it's too early to be talking about successes. You only know whether you were successful after you remove predator control. One of two things will happen. Either population levels will remain stable, or the population of game species will decline again. If the number of game animals declines again, you know you've mis-characterized the ecological situation, and you're attempting to apply predator control where it doesn't work; if they remain stable, you know that you've been successful**. I will admit, if you don't see an increase in game numbers, it is fairly indicative that your current predator control regime is not applicable.

If we're limited to current predator control areas, then the Southern Alaskan Peninsula Caribou Herd is not great example of anything, right now. The situation is complex, and it's my studied opinion that we're not entirely in possession of all the facts in that system.  While Calf Mortality is clearly a major issue with the SAPCH (<2 per 100 is a very low number indeed), I'm yet to be fully confident that there are not other, conflating factors involved in the long term population trends.

The AP left out something re: the non-resident hunter situation that I think ADF&G would have pushed strong for inclusion. That is, that non-resident hunters are a substantial economic factor, especially in small villages. In order to access the non-resident permitted areas, a guide is typically required. Further, non-resident hunting parties can spend several thousands of dollars per person, and each tag typically results in multiple hunters in a party. While the Nelchina is a complex situation, one that I swore I wouldn't touch with a 10 foot stick, game there is not so precariously positioned that those permits need to be cancelled.

One thing I wish people understood is that Predator Control is like science in general: It's really, really complex. There are no simple answers to pretty much anything; everything is wrapped up in assumptions that need met, confidence intervals, and highly situational knowledge. There should be an * beside pretty much every simple line inside these sorts of articles saying "Well, X is true 85% of the time, and the other 15% of the time, Y and Z are true." We're letting ourselves get trapped by these simple story explanations which don't even begin to cover the truth.


*Science by press release is a pejorative comment to describe non-peer reviewed science that's pushed out there by Public Offices of Agencies and Universities. the chief complaint is that science by press release is rarely accurate, and never goes through the rigour of peer review.


** This is seriously simplified, moreso than everything else here. But the nut of the matter is sound - you don't know, until it's over.

Hadn't we been on this ride before?

This comic panel from the ever-funny XKCD. Click for the whole strip...
The sad thing is, I know people like that. I'm boring by proxy!

Today I'm distracted from blogging by letter writing. Yet again, predator control is in the news for someone wanting to shut it down. Yet again, the whole thing is ignoring the science, and all about people's emotions. Management needs to be based on sound scientific principles, and not our whim of the day. Both the sides that think wolves should be protected because they're lovable and squeezable and the side that thinks wolves are awful and should all die are enemies of proper, rational, sound scientific based management which we claim is the goal. Cooler heads need to prevail; science frequently requires people to be dispassionately critical, something many people aren't used to being.

I really should have saved the last batch of letters, because I'm just going to say the same thing. Predator control works, but only some times. There appears to be instances where we've mis-applied it. Predator control is temporary, in an area, even if it might seem permanent as a program. The theoretical basis for predator control is strong, but only in some situations. Predator control is not the same wolf hunting the states engaged in during the 19th century. Predator control is incredibly expensive. Predator control is not about the predators, but about the game species. Predators in Alaska are not threatened like they are in the states.

If it sounds like I've been through this before, yes, I have. Endlessly. In fact, the first thing people ask me is often "Do you shoot wolves from a plane?" or some variation of that. Most of the time, by the end of the conversation, they're reading whatever answer they want to hear from my reply. People are too used to treating this as a visceral topic, and not used to treating it like a matter of science. I'd say that has to change, but honestly, I don't see it changing.

Taxinomic Un-sure-ed-ness

I'm starting to look into the systematics of wolves, in preparation for a potential project. Systematics is the study of naming things as species, subspecies, genera, families, and so on. It's all the Latin you see thrown around after common names. The rules are arcane, complex, and written by rich dead guys from Europe who didn't know that biologists would be doing what we're doing with it today. People have tried to redesign the rules from time to time, but it rarely is met with success.

You think it'd be easy to say what a species is. After all, we're always talking about this species, or that species - it's the most fundamental unit of population biology. Superficially, it's easy to point to brown bears and Pintail Ducks and say "Oh, yes, different Species for sure!" But when you get to coyotes and wolves, how about then? Wolves and dogs? The rules start getting very fuzzy.

The dirty secret of biology is we're not sure how to define a species. There are as many as 22 different ways to define species, with little agreement between them. Some heathens, like myself, are beginning to doubt that species actually exist as "a discrete biological entity." I envision sliding scales of similarity where populations are free to become less similar through isolation, or more similar through interbreeding. I imagine a few numbers that describe, say, `bear-ish-ness,` where Brown Bears, Black Bears and Polar Bears all have different values. The idea of a monotypic species is beginning to become very suspicious to me.

So if there's so much uncertainty, fuzziness and doubt around what is and isn't a species, imagine how much there is around the idea of a subspecies. Depending on who you talk to, there's between one and sixteen subspecies of brown bear in Alaska. The truth probably lies closer to the smaller value.

This unclaritude is reflected in wolf systematics. According to once source, there were 5 recognized subspecies and two species of wolf in North America. According to another, there was twenty four subspecies and two species. That's a heck of a lot of space between the two. While I write this, there's probably someone out there conspiring to name yet another subspecies, ranging the estimate up towards 25 or more in North America. I don't envy the sucker who has to wrap their head around all this.

Oh, that sucker's me, isn't it?

I present C. Lupus Zoalis
Common Name: The Zoo Wolf.
Type Specimen: Anchorage Zoo

What is "Game?"

I have some time before House M.D. starts, and I'm using it to pre-write a blog post. A pre-written post? Slacker!

Last Friday, as part of our department's regular seminar series, we had in a wonderful speaker, who's name has unfortunately slipped my mind. We talked after the seminar, as I wanted to discuss some follow up points, and the obligatory question of what I researched came up. Among my peers, I mostly explain that my lab studies game species, especially the genetics, but other issues like land use, and demographic history. She says its a shame that I don't study carnivores (she does), and this leaves me momentarily stumped. Well, actually, my lab does - we have a running wolf project through one of our grad students. But aren't they game?

In retrospect, the confusion was obvious. No, carnivores aren't typically thought of as game species. Alaska's one of the few places left where non-ungulates mammals are considered an important cultural, nutritional and economic resource. Lower 48 Brown Bears are in-part threatened (where they've not be outright expatriated) and the Black Bear harvest isn't typically significant. Fur-bearers are the obvious exception to this, but even then, the selection of fur-bearers outside is often reduced over those available north of WY.

I can't help but speculate this is a contributing factor in the many perceptions of wildlife resources. While for some, these species might form an important dietary and cultural resource, people not engaging in those activities may either not perceive the possibility of these activities, or fail to appreciate the importance of them. It also raises to mind how people in urban situations frequently fail to appreciate the sources of subsistence foodstuffs - people tend to assume there's much more red meat than there often is, as they place more importance on large ugulates over fish, waterfowl, regular fowl, marine mammals and plants. Going back to the wolves, it likely never emerged on the speaker's radar that wolves could be considered game, because it just never happens in California.

It's something to consider. And it'll definitely give me pause to be more clear when I discuss `game` issues. It'll do me no good to talk at cross definitions.

Wood Cutting from Round-About Rambles

Random bits of news

Here's a few stories that caught my eye this morning - I had a little extra time while waiting for my truck to melt to the point where it'd start. Kids, don't forget to plug in at night! (Actually, I only thought it'd get down to -20°C. Not -30°. Oooops.)

• Demand for apartments and cabins is down, according to this story by The Fairbanks Minor News. There are more postings than I remember, but also, they're still as over-priced as ever. Most of these places are cardboard boxes with fridges. And they charge 500 a month. Go figure.
• ADN linked to a story in Backpacker about conflict between trappers and wolf advocates near Denali National Park. Backpacker is usually a good magazine - I bought my father a subscription, once upon a time - but I think they're a bit heavy handed here. One thing I did notice is that there seems to be a lot of treating wolf packs as stable social units, instead of dynamic entities.
• The FBNSB is considering a trade in program for old boilers and wood stoves, writes the Minor News. I like this idea, as it tackles two problems, heating costs and air quality, by tackling inefficiency. I think about how much heat is wasted by the old oil drip-heater in my last home, it just makes me shudder a bit. The commenters on the story promptly jump the shark by accusing the bourgh of being out to steal their money, guns, and wood stoves. Fairbanks brightest and best, as always.