Dolphins Get 40s Flab, Too
upstart writes:
A Duke University-led study finds that bottlenose dolphins burn calories at a lower rate as they get older, just like we do.
It's the first time scientists have measured an age-related metabolic slowdown in another large-bodied species besides humans, said first author Rebecca Rimbach, postdoctoral associate in evolutionary anthropology at Duke.
Rimbach has studied energy expenditure and other aspects of physiology in animals ranging from mice to monkeys. But data on the inner workings of marine mammals such as dolphins and whales have been scant, she says. That's because these ocean dwellers are notoriously difficult to recapture for repeat measurements.
[...] The researchers studied 10 bottlenose dolphins aged 10 to 45 living at two marine mammal facilities, Dolphin Research Center in Florida and Dolphin Quest in Hawaii.
To measure their average daily metabolic rate, the researchers used the "doubly labeled water method." Used to measure energy expenditure in humans since the 1980s, it's a method that involves getting the animals to drink a few ounces of water with naturally occurring "heavy" forms of hydrogen and oxygen added, and then tracking how long the animals take to flush them out.
[...] The researchers expected dolphins to have revved-up metabolisms, since dolphins are warm-blooded just like people, and keeping warm requires more energy in water than in air.
But despite living in a watery world, they found that bottlenose dolphins burn 17% less energy per day than expected for a marine mammal of their size.
The scientists also noted some of the same signs of metabolic aging common in people. The oldest dolphins in the study, both in their 40s, used 22% to 49% fewer calories each day than expected for their body weight. And similar to humans, more of those calories ended up as fat rather than muscle. Dolphins in their 40s had body fat percentages that were 2.5 times higher than their under-20 counterparts.
Journal Reference:
Rimbach, Rebecca, Amireh, Ahmad, Allen, Austin, et al. Total energy expenditure of bottlenose dolphins (Tursiops truncatus) of different ages, Journal of Experimental Biology (DOI: 10.1242/jeb.242218)
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