Metro

Traces of hormone allow scientists to detect stress in whales

A North Atlantic right whale entangled in fishing ropes.
New England Aquarium
A North Atlantic right whale entangled in fishing ropes.

A new study of more than 100 North Atlantic right whales over 15 years shows the analysis of a hormone product in the animals’ waste can provide information on their stress levels and health.

“These levels show stress from extreme physical trauma,” lead study author Rosalind Rolland, a senior scientist at the Anderson Cabot Center for Ocean Life at the New England Aquarium, said in a statement.

“It’s an animal welfare issue,” she said. “For the first time, we can get hormone levels on not just dead but living whales.”

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The study, published this week in Endangered Species Research, covers the “pioneering technique” developed by Rolland used to examine feces taken from 125 right whales from 1999 to 2014. That group included a mix of 113 healthy whales, six that were “chronically entangled” in fishing gear, one that stranded for several days, and five that were quickly killed by vessel strikes, the aquarium said.

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Almost immediately after a stressful incident such as a stranding or entanglement, the hormone glucocorticoid is released into a whale’s bloodstream. The hormones then show up in whales’ feces one to two days after the incident, the aquarium said.

Researchers analyzing the waste found that the metabolized products of glucocorticoids appeared in the feces of whales that went through prolonged strandings and entanglements, but not the whales that died quickly from a vessel strike. The difference in hormone levels showed the researchers that the hormone can be used as a “biomarker” for chronic stress.

“This is one more tool in the toolbox for determining cause of death,” Rolland said.

The new research comes at a time in which a rise in fatal North Atlantic right whale entanglements have triggered an “unusual mortality event” for the species. Of the estimated 450 animals left in the oceans, 17 have died so far this year — a significant jump from the one to four deaths reported annually since 2011.

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Whales that become entangled in fishing ropes can carry the gear for months to years, as it cuts into their bodies or weighs them down. Chronically entangled whales can die of infections from their wounds, or from drowning.

If freed, the whales often end up enduring long-term stress that can seriously affect their health, the aquarium said.

The Anderson Cabot Center estimates that 83 percent of North Atlantic right whales have experienced at least one entanglement, with more than half of those experiencing more than one such incident.

Rolland hopes the effective study of glucocorticoids in whale’s feces will help to shed light on the growing entanglement problem and prove useful in better analyzing living whales without disturbing them in their habitat.

“When we started this in 1999, there was no existing methodology to study health on a living right whale,” she said.

Ben Thompson can be reached at ben.thompson@globe.com. Follow him on Twitter @Globe_Thompson.