Why more dead whales are washing up on US beaches: NPR
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Researchers are trying to unravel a mystery: why are so many humpback whales, right whales and other large mammals dying along the east coast of the United States? One possible explanation is a change in eating habits. And while theories are circulating that blame the growth of the offshore wind industry, scientists say there is no evidence to support this idea.
Since Dec. 1, there have been at least 18 reports of large whales stranded along the Atlantic coast, according to the Marine Mammal Stranding Network. The losses are hitting populations that were already under surveillance, due to the continued increase in unexpected deaths.
“Unfortunately, it’s been several years since we’ve had high strandings of large whales, but we’re still concerned about this spike” in deaths that’s now been going on for weeks, as Marine Mammal Health coordinator Sarah Wilkin and Stranding Response Program, said during a recent call with reporters.
Scientists are particularly concerned about the recent spike in deaths, Wilkins said, because the increase is seen in “a relatively small geographic area” and over a short period of time.
Here is an overview of what is happening and some of the possible reasons:
Which species of whales are experiencing spikes in deaths?
On the East Coast, two species of whales — the humpback whale and the North Atlantic right whale — have each suffered a spike in deaths in the past six or seven years, according to the National Oceanic and Atmospheric Administration.
The agency declared an unusual mortality event, or UME, for both types of whales. It defines a UME as an unexpected stranding that “involves significant mortality of any population of marine mammals” and requires an immediate response.
Since 2016, 180 humpback whales have been stranded on the coasts of American states, from Florida to Maine. At least seven strandings have already been reported in 2023, including four in New Jersey, equaling the state’s total in 2022.
For right whales, more than 20% of the population has been affected by documented EMU since 2017, an alarming statistic for an endangered species that, according to the latest estimates, still numbered 350 whales. The UME figure includes whales found dead, injured or sick.
On the west coast, NOAA tracked an UME involving gray whales. Since the start of 2019, 303 gray whale strandings have been reported in the United States. If Mexico and Canada are included, the total number rises to 608. More than a third of these deaths occurred in the first year of EMU; the numbers have fallen sharply since.
The three whale species in question have already been hunted to the brink of extinction. And while gray and humpback whales have rebounded, right whales remain an endangered species, with more deaths than births each year.
What about disruptions caused by offshore wind farms?
Even at the start of the unexpected strandings of humpback whales, questions were raised about possible damage to whales from wind farms. These questions have arisen during the current wave, as interest in offshore wind energy projects that require the use of powerful devices to map the ocean floor increases.
The questions have only intensified over the past two months as crews conduct surveys off New York and New Jersey for details of the seafloor, both to find out where the facilities could be located and where the cables could be installed.
The New Jersey-based group Clean Ocean Action has called for a halt to ocean wind projects and an investigation of potential harm to whales. Local and state officials have joined in this effort, as well as several members of Congress.
But officials from NOAA and other agencies are pushing back against suggestions that wind farms could somehow contribute to whale deaths.
“There is no known link between this offshore wind activity and the stranding of whales of any species,” said Benjamin Laws, deputy chief of the NOAA Fisheries Permits and Conservation Division, during a conference call.
The type of equipment used in the region isn’t as problematic as projects like marine oil and gas exploration, said Erica Staaterman, a bioacoustician at the Bureau of Ocean Energy Management’s Center for Marine Acoustics.
“The ones in oil and gas are called seismic airguns, and they’re specifically designed to penetrate miles into the seabed. So they’re very high-energy, very noisy sources,” Staaterman said. . In contrast, she added, the tools used to prepare offshore wind sites are “high-resolution geophysical sources, and they are typically smaller in the amount of acoustic energy they put into the column of water”.
“A lot of them are used for very short periods of time with a long period of silence in between,” Staaterman said, adding that some of the instruments also produce “a very narrow cone of sound,” rather than having it. explode in all directions.
“I just want to be clear,” Laws said, “there is no information that would support any suggestion that any of the equipment used to support wind development [to perform surveys] could directly result in the death of a whale.”
So what kills whales?
Overall, experts say human interactions are one of the biggest killers of whales, through collisions with ships or entanglements with ropes and other fishing gear.
It’s a particular threat this winter, when animals that are usually preyed upon by whales would have approached the shore, according to NOAA officials. This change leads humpback whales and other whales to follow, creating more overlap where whales and ships share the same waters.
And as Wilkin notes, whale population growth could be a factor. “As the abundance of whales increases, we will have more whales in different places,” she said.
For right whales, the agency says human interaction is the leading cause of death. About half of the humpback whales that died in the recent spike underwent some level of autopsy, according to NOAA. Of this number, approximately 40% showed signs of collision or entanglement with a vessel.
The causes of whale death can only be determined in a fraction of cases, in part because of the difficulty of examining a whale that dies in the wild, from its enormous size to the various states of decomposition that might have occurred. .
For UME affecting gray whales in the Pacific Ocean, the cause is still undetermined, although the researchers note that among the dead whales that were examined, several had “evidence of emaciation”.
One thing that ongoing UMEs on both sides of the coast have in common is their large scale: while historically some UMEs have been highly localized, tracking maps show that strandings of humpback, gray and outbursts have occurred along the Atlantic and Pacific coasts. .
It’s a stark contrast to previous clusters of deaths, like the 14 humpback whales that died of a biotoxin in 1987 – all in an area around Cape Cod, Mass. In this case, the deaths were attributed to saxitoxin, which is produced by red tide algae and can accumulate in mackerel – which the whales then eat.