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Right Whales Are Shrinking In Numbers— New Study Shows They're Also Shrinking In Size

ARI SHAPIRO, HOST:

Critically endangered right whales are shrinking compared to past generations. New research finds that the whales are growing to be about three feet shorter than they were 40 years ago. Eve Zuckoff from member station WCAI explains.

EVE ZUCKOFF, BYLINE: To find out how long and fat a North Atlantic right whale is without being overly invasive, scientists motor a few miles into Cape Cod Bay and launch a drone 200 feet into the air.

(SOUNDBITE OF DRONE FLYING)

ZUCKOFF: Using aerial photographs to measure the whales over time, the researchers concluded that the mammal's growth is stunted. Their shorter and thinner, says Joshua Stewart, the study's lead author.

JOSHUA STEWART: The sort of first inkling that we had came from the folks who were collecting the data in the field, where, as the story goes, they saw what looked to be a really young whale, you know, a calf or maybe a 1- or 2-year-old. But it turns out that they were actually 5-year-old or 10-year-old whales that were smaller than a typical 2-year-old.

ZUCKOFF: The main threat to their growth is entanglement in rope and commercial fishing gear. On their migration routes from Florida to Canada, the whales navigate a maze of those ropes that can wrap tightly around their flippers, tails and heads, often killing them. But when they do survive, the resulting stress from dragging heavy gear means the whale's energy is diverted away from growth and reproduction.

STEWART: So you can imagine if you were - you know, if you had a sandbag tied to you and you had to go about your daily business, you'd be burning a lot of extra energy just dragging that sandbag around.

ZUCKOFF: In fact, they found that female right whales entangled while nursing produce smaller calves. There are only about 366 North Atlantic right whales left in the world, so less energy for reproduction and resilience is an existential threat to the species.

STEWART: Especially as a calf, you know, you're needing to grow really quickly in those early years, so you could have a lower chance of survival if you're smaller.

ZUCKOFF: Entanglements have increased over the last 40 years, and conservationists now say this paper published in Current Biology strengthens the argument that regulators need to better manage the lobster fishery. They say more investment is needed to develop ropeless fishing gear to save the whales.

CHARLES MAYO: Really, the species can't tolerate any further impacts, or its future really is sealed.

ZUCKOFF: That's Charles "Stormy" Mayo, a researcher at the Center for Coastal Studies in Provincetown, Mass., who did not contribute to the research. He says climate change, a shifting food source and collisions with ships could also play a role in the whale's decline. Representatives of the lobster industry say they've been unfairly blamed for entanglements and accused regulators of threatening their very existence as well. For NPR News, I'm Eve Zuckoff in Woods Hole, Mass.

SHAPIRO: And a quick note - it's just being reported that the 18th North Atlantic right whale calf of the season has been spotted in Canada's Bay of Fundy. That makes this year's calf count the highest since 2013, a small but meaningful win for the species.

(SOUNDBITE OF MUSIC) Transcript provided by NPR, Copyright NPR.