Scientists Explain Potential Reason Behind Unusual Whale Deaths

Ecosystem changes could be playing a part in the ongoing deaths of gray whales along the west coast of North America, according to researchers.

The gray whale deaths have been prominent in the San Franciso Bay Area, where The Marine Mammal Center (TMMC) told Newsweek it has responded to 13 incidents so far this year—more than in the entire years of 2019 and 2020.

Scientists have declared the event to be an unusual mortality event, or UME, and it started at the beginning of January 2019.

As of June 4 this year, the National Oceanic and Atmospheric Administration (NOAA) reported a total of 465 gray whale deaths along the west coast of North America in the ongoing UME. Many are making a northerly migration to cool, food-rich Arctic waters.

Researchers are still investigating the cause, but necropsies—a post-mortem examination of an animal—have revealed some clues.

Kathi George is the director of field operations and response at TMMC. She says some—but not all—of the dead whales found recently have shown signs of emaciation, meaning they appeared abnormally thin or weak.

George told Newsweek: "This suggests potential ecosystem changes that may be impacting their habitat and food availability.

"Climate change affects water temperatures and prey availability, leading to shifting food sources for marine mammal populations and other marine species."

According to Michael Milstein, public affairs officer for NOAA Fisheries, the emaciated condition of some of the whales suggests there may have been some sort of change in the availability of food in the Arctic, which is where most gray whales spend the summer feeding.

Yet these cases are not universal. Milstein told Newsweek: "While a substantial number of the stranded dead whales have been emaciated, not all of them have been, so that by itself does not explain the UME.

"Other causes of death include ship strikes, and some are currently unexplained. Many of the carcasses have been too decomposed to reveal much."

Other factors being considered are harmful algal blooms, infectious disease, natural predation, and human interactions.

It is not the first time something like this has happened. Another UME was declared in 1999, which lasted until 2000. Then, again, some of the whales showed signs of emaciation, but not all. Ultimately NOAA researchers were not able to pinpoint one particular cause, though Milstein notes changing food availability "may have been a factor."

In the current UME, it should be noted that NOAA data shows there have been fewer strandings overall in Canada, the U.S. and Mexico so far this year than at this point in time in each of the last two years.

In any case, activists are calling for change. On Tuesday, this week, local environmental groups gathered at San Francisco's Crissy Field in what they called "a wake for whales" to acknowledge the losses reported in the area so far this year.

Part of the protest was focused on climate change, but activists also called for a 10-knot speed limit through and around the bay to help prevent deadly ship strikes, CBS San Francisco reported.

Others called for new ropeless crab traps, blaming entanglement in roped traps as another cause. Mike Conroy, executive director of the Pacific Coast Federation of Fishermen's Associations, told CBS San Francisco that existing limits were effective enough and feared mandatory ropeless traps could put fishermen out of business.

For now, researchers are calling on the public to report any deaths as soon as they see them. The NOAA stranding hotline can be reached on 1-866-767-6114. George said state and city officials can assist with funding support and access for necropsies.

Beached whale
A beached gray whale, pictured April 2021 at Muir Beach in Marin County, California, which died to blunt force trauma due to ship strike. The Marine Mammal Center