Where’s Rudolph? Inside the Decline of Alaska’s Caribou | Science | Smithsonian
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Where’s Rudolph? Inside the Decline of Alaska’s Caribou

The antlered herd’s population is declining – what’s going on in the Alaskan wilderness?

smithsonian.com

As Christmas approaches, young eyes will be focused on the sky searching for a glimpse of Santa and his reindeer—or are they caribou? The differences between the two are mostly taxonomic—both are subspecies of Rangifer tarandus, but Jim Dau of Alaska’s Department of Fish and Game is quite familiar with the subtleties of the antlered cousins.

Dau studies the Western Arctic caribou herd, among the largest in the world at 300,000 strong, that ranges over an area about 143,000 square miles in northwestern Alaska. While those figures might sound impressive, the caribou population has been steadily declining since 2003, when the herd peaked at nearly half a million. The decline is a source of concern for biologists studying the trend’s effects on the food chain, as well as for the more than 40 native villages that rely on the animals for food and as a cultural centerpiece.

The herd’s calving grounds are located within the National Petroleum Reserve-Alaska, also home to North America’s largest coal deposit. Currently, the Bureau of Land Management, which oversees the NPR-A, is in the last stages of finalizing the NPR-A’s new management plan—a document that will be instrumental in dictating the future of the Western Arctic caribou and to what degree energy development might infringe on the caribou’s turf.

Dau has spent the last 25 years living in remote Arctic villages in order to study the regal beasts.

Aside from the fact that caribou aren’t employed to haul Santa’s sleigh, what’s the difference between reindeer and caribou?

In North America, reindeer can be privately owned while caribou are wild animals that are public resources.

There are also biological differences between North American reindeer, which were transplanted to northwestern Alaska from Europe beginning in the late 1800s, and caribou. For example, the whole annual cycle of reindeer is one month ahead of that for northern Alaska caribou—for example they rut a month earlier and give birth a month earlier.

As well, there are physical and behavioral differences between them. Caribou tend to be taller and rangier than reindeer; as a result, caribou can run much faster than reindeer. Female reindeer tend to be heavier with larger and more fully developed antlers than adult cow [female] caribou. For bulls, these differences are reversed. Although most reindeer are colored similarly to caribou, reindeer are occasionally white or spotted while the pelage of caribou rarely varies. Caribou are generally much less trusting of man than reindeer, although the latter quickly become increasingly wild when untended by herders.

The Western Arctic Caribou herd’s annual migration may not be as famous as the reindeers’ mythical trip on Christmas Eve, but it’s amazing in its own right.

During the fall migration caribou are often spread throughout most of their range. For the Western Arctic Caribou Herd this encompasses about 143,000 square miles. An individual caribou from this herd may migrate 300 to 500 straight-line miles from the beginning to the end of its migration. Of course, caribou don’t move in straight lines, for more than several seconds anyway, and an individual may travel several times that distance during the course of a migration as it searches for food, evades predators and seeks out other caribou.

In two different years, during the height of the fall migration, I’ve watched as the entire herd stopped. Not for four or six hours but for two to three weeks. Then, within a several-day period, they resumed the fall migration. They must have keyed off some large stimuli, such as weather. But I don’t think it was just that because their halt and resumption of travel were so synchronous. It seemed like caribou that were separated by tens of miles and large geographic features, such as mountains, were somehow aware of each other’s movements. I don’t know how they could do that, but I suspect we grossly underestimate the sensory capabilities of caribou.

Rut happens during the fall migration, which is really an exciting time. Group sizes tend to get a little bigger during rut, and bulls become totally obnoxious chasing cows, other bulls; they pose to show off their antlers and grunt continually. It’s the only time of year that bulls vocalize.

In the spring, pregnant cows start migrating north about three weeks ahead of the bulls, and it’s pretty much a steady plod with these big long lines written out in the snow. It’s just beautiful to see these almost serpentine trails weaving out over the hills and mountains.

The Western Arctic Herd is the largest in the United States—aside from bragging rights, what’s the significance?

The herd’s ecological importance is incredible. It affects the entire food chain, all the way from bacteria to the biggest predators, such as wolves and brown bears. They affect the vegetation not just by what they remove with their lips by but trampling. They not only remove nutrients and energy from the environment, but contribute back towards the whole cycle with their feces and urine. They shed antlers and eventually their bodies and skeletons after death.

They’re also incredibly important to people. The Inupiaq people have subsisted on marine mammals and terrestrial mammals, like caribou, for thousands and thousands of years, but it’s more than just a source of protein for them. Caribou are really central to their cultural identities and many of their customs, such as the development of extensive social networks for sharing subsistence food that go along with hunting and using caribou.

They’re also incredibly important to the commercial operators who transport hunters, hikers or floaters, the people who come up here from the Lower 48. Regardless of where people live or why they visit remote portions of Alaska, an opportunity to see thousands or even tens of thousands of caribou in a one to two week period is truly memorable.

What’s to blame for the herd’s declining numbers?

I’ve lived here and been a biologist for 25 years; I fly up to 600 hours a year looking at caribou and I talk to literally hundreds and hundreds of people, asking them the same question you just asked me. I don’t have any hard data to tell you.

Here is what I think is going on. In the last six, eight, ten years, we’ve had more rain on snow events than we used to. We’ve had more moisture fall, and it’s created icing conditions that seal the food. There’s food down there, but either the caribou can’t get to it, or when they finally do get to it, they’ve expended more energy getting there than they get out of it. I think that is what tipped the balance and started this herd going down.

I can also tell you I’ve seen more wolves in the last three to five years than I ever have, and brown bear numbers seem to be going up. That’s what virtually every villager I talk to tells me as well.

If caribou numbers continue to decline, how will this look from a biological perspective?

The decline of this herd will have a ripple effect that will be felt by virtually all animals, species and all the people that use them. Some years some villages have had a really tough time getting caribou. They don’t sit at home waiting for caribou, they a take moose instead. So there’s a shift by people towards other animals they can eat. Predators are the same way.

These oscillations are absolutely natural. Part of me wonders if it may be necessary for caribou habitat to be able to enjoy periods of time when caribou numbers are low so that they can kind of rejuvenate too.

After three decades studying the Western Arctic herd what keeps you interested?

You hear this in all walks of life—the more you know the more you realize you don’t know—especially now when there are so many more tools available to analyze data.

But, what really keeps me most interested isn’t in the office. It’s out in the weeds; it’s out in the country. What floats my boat is to be out looking at the land, looking at the caribou and all the other animals that share that country with them.

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