Planet Earth

Elderly Seabirds Dive Just as Well as Young Ones

InkfishBy Elizabeth PrestonSep 9, 2014 5:37 PM


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If your grandma got up from the sofa, did a couple toe-touches, and then ran a mile at her college track pace, she might be approaching the athletic skill of a thick-billed murre. These seabirds make incredibly deep, long dives to catch prey. As they age, their bodies slow and change like ours. But the athleticism of their dives never changes—a feat that might help scientists understand the enigmas of aging. "Most of what we know about aging comes from lab animals," says Kyle Elliott, a graduate student at the University of Manitoba. These short-lived flies, worms, and mice tell scientists very little about how long-lived wild animals age and die. Even a wild fly or rodent can expect to end its life as another animal's meal. But when an animal is likely to live for decades, how does its biology change over time? What eventually kills it? Does cancer or poor cardiovascular health change its life expectancy? "There are certainly an awful lot of open questions," Elliott says. To find out a little more, he and his colleagues studied the thick-billed murre, Uria lomvia. These auks have black bodies and white bellies like penguins, but live at the opposite end of the earth. They swim and go diving for food in chilly northern oceans. They can travel as deep as 170 meters and stay under for up to 5 minutes, Elliott says, which is "an amazing feat for a 1-kilogram bird." Penguins of the same size can't dive nearly as deep or as long. (Plus murres can fly. Sorry, penguins.) Elliott examined birds breeding in Nunavut and found individuals ranging from 3 to 30 years old. He measured the oxygen stored in their blood, their levels of thyroid hormones, and their resting metabolism. One year and three years later, he returned to repeat these measurements. He also attached recorders to birds' legs and backs to track their dives. The murres' bodies showed clear signs of aging. Over the years, their blood became able to store less oxygen, and their metabolisms slowed. But the difficulty of their dives never changed. How were birds able to keep up their lung-busting dives in old age, when they couldn't take as much oxygen down into the ocean with them? Elliott says the rate at which birds used up oxygen seemed to compensate for their shrinking stores. "Generally, I think it might be true that our bodies tend to compensate for deterioration of one component by altering another," he says. For example, more recent (unpublished) research has found similar trends in flight as in diving. For all kinds of physical feats, older birds might make up for their slowing bodies by tapping into their greater experience. Elliott also reviewed other researchers' studies of aging animals. He found that across the animal kingdom, from mussels to finches to humans, metabolisms slow down with age. And this happens more quickly for animals that use a lot of energy, like the diving murre. But wild animals may be able to compensate for those changes so that their behavior looks exactly the same. He thinks aging birds might maintain their athleticism simply because they can't afford not to. "I've never gotten on a passenger jet that is falling apart, but I've often ridden in some 'clunker' cars," he says. In other words, a bird that rockets its body along epic migrations or deep dives "can't compromise on performance." Elliott hopes new technologies for monitoring animals—as they live and die—will help biologists figure out how aging works in the wild. For conserving threatened species, it's important to know what keeps wild animals alive and what eventually kills them. But right now, he says, "We have no idea."

Image: by Tony Morris (via Flickr)

Elliott, K., Hare, J., Le Vaillant, M., Gaston, A., Ropert-Coudert, Y., & Anderson, W. (2014). Ageing gracefully: physiology but not behaviour declines with age in a diving seabird Functional Ecology DOI: 10.1111/1365-2435.12316

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