Counting the breaths of wild porpoises reveals their revved-up metabolism

[Judi Lynn]

In Danish waters, these small cetaceans have metabolic rates more than double those of humans
BY SUSAN MILIUS 6:00AM, DECEMBER 14, 2018



JUST BREATHE A method that tracks harbor porpoises’ breathing helped scientists verify claims of high energy needs in the free-swimming mammals.


By counting harbor porpoise breaths, researchers have come up with a new way to judge the animals’ hard-to-measure metabolism. The trick shows that the animals can burn energy more than twice as fast as humans.

Researchers analyzed the several thousand puff-huff respiratory sounds recorded per day from each of 13 harbor porpoises swimming freely in Danish waters. Including just everyday staying-alive body processes plus hunting and other activities, the animals’ average total energy use ranged from 7.8 to 31 megajoules per day, researchers report December 6 in the Journal of Experimental Biology.

The five adult porpoises (Phocoena phocoena) studied averaged 21.7 megajoules per day. A typical human weighing about as much as a full-grown porpoise, however, needs only about seven to nine megajoules of energy daily, says study coauthor Peter Teglberg Madsen, an eco-physiologist at Aarhus University in Denmark.

Madsen says the animals’ high energy needs in the chilly waters close to Danish shores leave him “somewhat worried.” Harbor porpoises there depend on small fish, even down to pinkie finger–sized ones. But to survive with such a high metabolic rate on small prey demands steady hunting. And Madsen fears that increasing human disruptions in the ocean are making that difficult for the ocean mammals (SN: 2/13/18).

More:
https://www.sciencenews.org/article/counting-breaths-wild-porpoises-reveals-their-revved-metabolism?tgt=nr