How do you get to know a whole herd of elephants -- or a mob of manta rays?
Most of what we know about animals comes from scientists who patiently study these creatures in the wild. To really understand one kind of animal, these field biologists need to find out what the creatures do every day.
Think of how field biologists would study students at your school. They'd go there and ask themselves questions: How many students are there? How do they reach the building? What do most students eat?
Then the scientists would want to figure out who the individual students were. Once they could tell one student from another, they could find out other things: Who does this person hang out with -- or not hang out with? Which kids are in the same family? Who eats more food in the cafeteria: younger or older kids? The more information they got, the better the scientists could understand how student life works.
But how do you recognize the same individual animal over and over again? How do you tell one elephant, whale or leopard from another?
"It's a bit like recognizing a friend. You know that friend by a number of different features, some of which you wouldn't even be able to describe," says Cynthia Moss. She's studied elephants in Kenya for 30 years. Here's her trick: "When I get close to an elephant and see its ears, I can make a positive identification."
Moss says each ear has its own pattern. Some have nicks and tears, and some have warts. There are other features that make each elephant different as well, such as size and tusks and whether the creature is good-looking. "Elephants can be pretty or ugly or funny-looking," she admits.
Moss and her assistants make a photo album showing each elephant. When others watch the elephants, they use the album to help identify who's who.
Okay, that's how you identify elephants. But how do you tell one humpback whale from another? Scientists look at their flukes (tails). Each humpback's tail has different nicks, tears and markings. Scientists from Cascadia Research, for example, photographed 1,300 humpback whale tails, and use these photos to ID the whales as they migrate along the California coast each year.
But pity the poor scientist trying to compare hundreds of photos. Some groups of scientists use computer-assisted photo identification programs to help them at least narrow down which animals seem similar. Then the scientists can check the computer's selection to see which ones really match.
Mobs of Mantas
One scientist decided to try the same computer technique on the group of animals he was studying -- giant manta rays. For five years, Paul Ahuja has studied these rays along the west coast of Mexico.
Doesn't one ray look pretty much like another?
"Well, at first glance, yes -- and that's a problem," Ahuja says. "But when you swim under them, you can see the rays have pigment markings on their bellies, like black spots on a white cow. Each ray's markings are a little different and don't change over time." That's important. You don't want to identify an animal only by something that changes, such as their size or antlers. It's like identifying people by their haircut instead of using, say, their eye color.
You also want to identify an animal by a feature that seems the same no matter how you look at it. For example, leopards are identified by the markings on their foreheads. But the spots on a leopard's forehead can look different from different angles. So scientists use the markings around the animal's eyes and whiskers as their ultimate ID.
By being able to recognize the same animals year after year, scientists learn what kinds of food, companionship and space these animals need. And the more we know about how animals live in the wild, the better we're able to figure out how to support them.
-- Deborah Churchman