North Atlantic right whales – a highly endangered species making modest population gains in the past decade – may be imperiled by warming waters and insufficient international protection, according to a new Cornell analysis published online in Global Change Biology, Oct. 30.

“In the 1990s, right whale population growth slowed due to poor feeding conditions, low calving rates and high numbers of deaths due to ship strikes and fishing gear entanglement. But during the following decade in the 2000s, feeding conditions improved, and the whale population started to recover,” said author Erin Meyer-Gutbrod, Ph.D. ’16, who conducted the work as a doctoral student and postdoctoral researcher in the laboratory of Charles Greene, professor of oceanography and co-author on the paper.

North Atlantic right whales’ preferred cuisine is copepods that thrive in cool waters, such as the Gulf of Maine, said Meyer-Gutbrod. Scientists once relied on continuous plankton sampling to track the copepods, but the National Oceanic and Atmospheric Administrations’ National Marine Fisheries Service discontinued the program, preventing researchers from observing ecosystem changes as they occur.

In the past several years, a smaller portion of the right whale population has been seen in the Gulf of Maine as it has warmed, and the whales have been spotted farther north than usual, in the Canadian Gulf of St. Lawrence, likely in search of the small crustaceans, she said.

Because whales used to be rare in the Gulf of St. Lawrence, northern waterways lack whale protection policies. Without adequate policies the whales are at greater risk from ship traffic and commercial fishing gear.

Sixteen North Atlantic right whales were found dead this year in the Gulf of Maine and the Gulf of St. Lawrence. Out of the seven carcasses that could be necropsied, six were caused by humans as a result of ship strikes or fishing gear entanglement.

“Right whales are a highly endangered species with approximately 500 animals remaining,” said Meyer-Gutbrod, who now works at the Marine Science Institute at the University of California, Santa Barbara. “This crisis signals a major shift in the whale population’s recovery, corresponding to a loss of 3 percent of the right whale population.”

The paper’s projections indicate that when 13 additional right whales suffer human-caused deaths annually, assuming typical prey conditions, the species may start to decline.

If prey availability is limited, losing just 10 additional whales annually could signal a decreasing population. “That’s why the discovery of 16 carcasses, and the knowledge that the true number of mortalities is probably much greater, is a serious problem for these charismatic giants,” said Meyer-Gutbrod.

Said Greene: “There is a very important interaction between climate change and anthropogenic mortality factors. We must extend whale protections to prevent a major decline in the population.”

The work, “Uncertain Recovery of the North American Right Whale in a Changing Ocean,” was funded by the National Defense Science and Engineering Graduate Fellowship and by Cornell’s Atkinson Center for a Sustainable Future, through its Sustainable Biodiversity Fund.