Are some great animial migrations in peril?

11/30/10 Seán Kinane
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What drives billions of animals to make epic migrations every year and how are migrations being affected by habitat destruction and climate change?

To address these important ecological questions, WMNF spoke with Karen Kostyal, author of the National Geographic book Great Migrations. It's is a companion to the National Geographic Television series of the same name.

"Well, I think there are two really compelling reasons animals migrate. We've called them the 'need to feed' and the 'need to breed' and really those two things are at the bottom of almost all migrations. They're migrating to perpetuate the species and they're migrating in a search for food or water and the two instincts are really combined because if you look at African animals, the large animals that we've featured in the book, Mali elephants, the Wildebeest of the Serengheti, zebras, a newly discovered herded animals called the White Eared Kob. All of those animals are moving with the rains, because the rains green up grasslands, the animals move in behind the rains, they're following the rains, the looking for the rains and they're moving in a loop as the seasons change, following the rains. And as they do that they time their breeding cycle to times of plenty and to how it will work for the young animals to follow them in their migratory loops. So it's all, as I've found with everything to do with migration, it's all an intricate dance."

How are these animals guided? How do they plan the timing and the direction of their migrations?

"Well these are age old migrations, most of them, and the animals are, as one scientist put it, animals that migrate are really over engineered, especially the long distance migrators. They have so many devices that they're equipped with to guide them on the migration. Some of the most, actually I thought. profoundist, they're taught their migratory routes by the generation ahead of them. They learn them, they learn to memorize the landscape, they move sometimes by odors, they're following odors, they're following sights, just as we turn at that store because that's the way to get to the place we want to go, they do something like that. But then they have more sophisticated devices we don't have. Many animals have a sun compass which means that they can read kinds of light that we cannot read, they can read polarized light so that on a cloudy day they can keep going with the migration. Some can detect ultraviolet light and that allows them to use that light to guide them. And then of course, there are animals, and among them are monarch butterflies that actually have pieces of magnetite embedded in their bodies and that allows them to use the Earth's geomagnetic field to guide them on their migratory routes. So there are lots of different ways animals manage their migrations."

We're speaking with Karen Kostyal, author of "Great Migrations", tell us about some really notable migrations, especially maybe the Arctic Tern which travels 44,000 miles and some of the other ones that you might think are notable?

"The Arctic Tern is an amazing animal, I will tell you it's mentioned in the book, it's not one of the animals that we featured. But there are numbers of migrations that I thought...almost every migration that I wrote about really kind of amazed me. One animal that I'll discuss because it is in trouble, a number of these animals are in trouble for various reasons, generally because their migratory corridors are being interrupted by the human footprint, but one animal that's very obviously being affected these days by global warming are the Pacific Walrus. They spend the winter months in the Bering Straits feeding on several islands and then as the weather starts to warm they move north above the Arctic Circle into the Chukchi Sea and the males haul out on some very specific beaches and spend the summer sort of sunning on these beaches and feeding in the waters offshore. The females and their young stay on icebergs and they use the icebergs as platforms for obvviously breathing because they are marine mammals and for stabilizing their journey north and then allowing them to be offshore and away from these huge gatherings of these enormous males because the pups can't really survive masses of bodies. What's been happening is with the ice disappearing the females and young have had to haul out on the beaches with the males and many young are not surviving that experience. So that was an animal that I was taken with the threats to it's survival at this point."

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