Primates Expend Less Energy
January 14, 2014

Primates Expend About 50 Percent Less Energy Than Other Mammals

[ Watch the Video: Half The Legs Equals Half The Energy ]

redOrbit Staff & Wire Reports - Your Universe Online

Humans and other primates burn 50 percent fewer calories each day than other mammals, and their slower metabolisms could explain why they mature slowly and live longer lives, according to a study published in Monday’s edition of the journal Proceedings of the National Academy of Sciences.

Furthermore, an international team of researchers led by Hunter College anthropologist Herman Pontzer found that primates living in zoos and those living in the wild expend equal amounts of energy, suggesting that physical exertion could have less of an impact on daily energy expenditure than most experts believe.

Pontzer and his colleagues worked with primates at Chicago’s Lincoln Park Zoo and similar facilities, as well as animal sanctuaries and in the wild. They examined the daily energy expenditure of 17 different primate species, including everything from gorillas to mouse lemurs, to determine whether or not a slow metabolism was responsible for the comparatively slow lifespan they lead in comparison to other mammals, such as dogs and hamsters.

“Using a safe and non-invasive technique known as ‘doubly labeled water,’ which tracks the body's production of carbon dioxide, the researchers measured the number of calories that primates burned over a 10 day period,” officials from the zoo explained in a statement. “Combining these measurements with similar data from other studies, the team compared daily energy expenditure among primates to that of other mammals.”

“The results were a real surprise. Humans, chimpanzees, baboons, and other primates expend only half the calories we'd expect for a mammal,” added Pontzer, who is also affiliated with the New York Consortium for Evolutionary Primatology. “To put that in perspective, a human – even someone with a very physically active lifestyle – would need to run a marathon each day just to approach the average daily energy expenditure of a mammal their size.”

This marks the first time that this drastic reduction in metabolic rate has been detected in primates, and the study authors believe that it accounts for their slow pace of life. Energy is required by all organisms to grow and reproduce, and expending that energy can also contribute to the aging process.

The slower growth, reproduction and aging rates of primates match their slow rate of energy expenditure, according to the investigators. This indicates that their metabolic rate has evolved in order to help shape their less-fast-paced lives, and the conditions that favor this reduced energy expenditure could help scientists understand why humans and other primates went on to develop this slower pace of life.

Furthermore, the researchers said that their measurements demonstrate that primates living in captivity expend just as many calories during an average day as those living in the wild. They believe that this discovery demonstrates that creatures living in zoos and sanctuaries are being kept healthy and are well-cared for, and that physical activity might contribute less to a primate’s overall energy expenditure than previously believed.

“The completion of this non-invasive study of primate metabolism in zoos and sanctuaries demonstrates the depth of research potential for these settings. It also sheds light on the fact that zoo-housed primates are relatively active, with the same daily energy expenditures as wild primates,” said study co-author Steve Ross, Director of the Lester E. Fisher Center for the Study and Conservation of Apes at the Lincoln Park Zoo.

“Results from this study hold intriguing implications for understanding health and longevity in humans. Linking the rate of growth, reproduction, and aging to daily energy expenditure may shed light on the processes by which our bodies develop and age,” the zoo added. “And unraveling the surprisingly complex relationship between physical activity and daily energy expenditure may improve our understanding of obesity and other metabolic diseases.”