Abstracts: Body Size Variation in Caribou Ecotypes and Relationships with Demography

One of the bigger arguments amongst Caribou biologists is what is the relationship between the different forms we see, and how important they are. For example, on one hand you have the big migratory herds like Western Arctic, but then you have more woodland herds like the Mentasta. Finally, there are sedentary montane herds. All three look like they have different things going on morphologically too, according to these authors. I'm fairly willing to believe that, and I'm willing to believe their mechanism - that it's habitat induced variation, and not anything genetic. That is to say, they're like that because they live there, and if they didn't live there, they wouldn't be like that.


Here's the abstract

ABSTRACT In many vertebrates size is one of the most influential and variable individual characteristics and a strong determinant of reproductive success. Body size is generally density dependent and decreases when intraspecific competition increases. Frequent and long- distance movements increase energy expenditures and, therefore, may also influence body size, particularly in highly mobile species. Caribou (Rangifer tarandus, also known as reindeer) exhibit tremendous variation in size and movements and thus represent an excellent candidate species to test the relationships between body size, population size, and movements. We analyzed body measurements of adult female caribou from 7 herds of the Que ́ bec-Labrador Peninsula, Canada, and we related their morphology to population size, movements, and annual ranges. The herds represented 3 ecotypes (migratory, montane, and sedentary). Ecotypes and herds differed in size (length), shape (roundness), and movements. The sedentary ecotype was larger and moved 4 to 7 times less than the migratory ecotype in the 1990s. At the start of a demographic growth period in the early 1960s, migratory caribou from the Rivie` re-George (hereafter George) herd had longer mandibles than caribou of the sedentary ecotype. Mandible length in the George herd declined in the 1980s after rapid population growth, while individuals performed extensive movements and the herd’s annual range increased. Migratory caribou then became shorter than sedentary caribou. After the George herd decline in the 1990s, mandible length increased again near levels of the 1980s. Caribou from the migratory Rivie` re-aux- Feuilles herd later showed a similar decline in mandible length during a period of population growth, associated with longer movements and increasing annual range. We hypothesize that the density-dependent effect observed on body size might have been exerted through summer habitat degradation and movement variations during herd growth. Our study has 2 important implications for caribou management: the distinctiveness of different populations and ecotypes, and the correlations between population trajectories and changes in body condition and habitat.

Couturier, Otto, Côté, Luther and Mahoney. 2010. Body Size Variations in Caribou Ecotypes and Relationships With Demography. J. Wildlife Management, 74, pp. 395-404. DOI: 10.2193/2008-384

Totally unrelated, but I met Shane Mahoney last year - I think it as at the Wildlife Soc. 2009 meeting, but I'm fuzzy on that point. He's an entertaining guy, and as smart as it gets. Côté is also very clever, though I been able to meet him directly yet.

Invading Soviet Canukistan

I've long been suspicious of Canada. After all, how could a country so big, with cold weather be so rotten at Hockey? Just look at the last time they came even close to the Stanley Cup. That just smells plain fishy to me. What's worse, they never told the Queen to take a hike like the US did. I think conflict between the US and Canada isn't just innevitable, but desirable. Let's finish what the country started in 1812! Luckily, there are already military plans in the works for our invasion of Canada... albeit from the 1930s.

We're coming for you, maple leaf loving jerks!

The future of Polar Bears is Styrofoam

There's a stock number of questions I get all the time. Usually the first question I get is something about whether I shoot wolves or not. But just as often, after a long discussion about predator control, I'll get asked about Polar Bears, and whether I support their listing.

My answer is, of course, that given my knowledge of Polar Bear biology (admittedly incomplete), it seems prudent to protect Polar Bears. People will then ask me if I support subsistence harvest for Polar Bears. Which, given my knowledge of Polar Bear ecology, I do. `Ah ha!` someone will cry. `You're biased to subsistence! You wouldn't let a bunch of white guys go out and shoot a Polar Bear, but you're happy to let natives do it even when you want to protect a species!`

This is when I get out the clue-by-four and begin beating them with it until they get a clue.

So how can a species need protection, but still be available to harvest? Well, unlike many things in biology, this is actually mostly straight forward.

Let's say you have a Polar Bear.

Yes, yes you are a Polar Bear. Incidentally, if you want my art skills using paint, check out this tutorial.

Okay, let's take that Polar Bear, and put it with all her buddies.

What a wacky bunch! They should have their own prime-time sitcom.

Now, in this system, we have something that is a limiting factor, and something that will become an increasingly large limiting factor - habitat. Particularly, ice habitat. We're going to have a lot less of it. Some Polar Bears are going to have it...

But what about those who won't? Or those who get sub-optimal habitat?

Well...

I joke. It's not curtains time for them, but those bears will be much worse off. The boars probably won't get to breed, and the sow will have very low cub survival, because the sows will be in poor condition. There may be some small contribution contribution to the next generation's numbers, but the contribution will be dominated by chance (stochasticity).

It's my contention, and the contention of US gov't., that harvesting a small number of Polar Bears is entirely acceptable (albeit unsustainable). If you shoot a Polar Bear, either a) it wasn't going to make a large contribution to the demographics (especially if male) or b) it frees up the limiting factor (habitat) for another animal who will now be able to make a larger contribution to the next generation. And if you keep your hunts low, the mortality will rarely make a blip on the population magnitude radar. The story is simplified slightly, yeah. And I glossed over a few things. But on the whole, it holds water.

"Wait! You said it was unsustainable. What's with that" Well, sure. Eventually, given the trends in habitat, there will be very little habitat left to Polar Bears. Short of building Styrofoam icebergs for them, there's nothing we can do about that. Thus, it's not a sustainable situation. However, it's got less to do with hunting pressure and more to do with people running coal fired power plants. Here's some cold hard facts to throw a damper on your day: There probably won't be many Polar Bears in the future, Yup'ik Language is dying, someone will have to take a cut in their lifestyle because every country can't all have it and Africans will eventually want to start eating food too, and eventually India will kick our ass economically. Oh, and there's no Santa.

So, that all said, the ban on importing Polar Bear rugs from hunts is pissing into an active volcano. Sure, it feels good, but it doesn't get anything done to Polar Bear conservation. Worse, it has the unintended consequences of cutting off the livelihood of people. And it will consume resources enforcing the ban which would be better spent doing conservation in other ways. Like, say, putting up a few few wind turbines. But if we were really serious about solving these problems, things would be different, wouldn't they?

Off to the east...

Who says I just do American politics? The Govern General, the Queen's representation in Canada, took part in a seal butchering in Nunavut. People are all atwitter over this, because catching seals is controversial in Canada (moreso than in the US).

I'm pretty glad she did. Ooops. Was that too moralistic?