Why do so many whales wash ashore in the US?

Nearly two dozen whales have been washed ashore on the US Atlantic coast in the past three months – some by boats and others that may have been caught due to changes in ocean currents associated with climate change.

Over the past three months, about two dozen large whales have washed ashore on the beaches of the US East Coast. The surge in strandings has experts worried about an already vulnerable species and has fueled speculation about potential causes of death.

Are these whale discards unusual?

Since December 1, 2022, 22 large whales have washed ashore off the US Atlantic coast, according to the US National Oceanic and Atmospheric Administration (NOAA). Among them are 15 humpback whales, 3 sperm whalestwo North Atlantic whalesone this whale and one minke whale. Whale mortality in the first two months of 2023 is already rivaling last year’s figures. “This is an alarming surge,” says Sheila Dean of the Marine Mammal Research Center in New Jersey.

This latest wave of whale deaths is part of a larger trend that began in 2016. NOAA is investigating an unusual event that took place over the course of seven years., but notes that this number of deaths at the beginning of the calendar year is not normal.

What species of whales are at risk?

Of the five species washed ashore in recent months, three are considered vulnerable or endangered: North Atlantic right whales, sperm whales and sei whales. humpback whales (Megaptera novaeangliae) and North Atlantic right whales (Eubalaena glacialis) are the species most commonly stranded on the Atlantic coast of the United States, although humpback whales typically account for the bulk of beached whales, which may be due to their being the most abundant whale in the area.

The situation for North Atlantic right whales is dire, with fewer than 350 left. The death of two right whales just a few weeks apart was a particularly hard blow for this species. More than 20% of the population has been affected by an unusual death since 2016, according to NOAA.

What is killing whales?

There is no single reason responsible for stranding every whale, although most stranded whales are sick or injured. In some cases, there are clear clues: Several whales washed ashore in New Jersey had deep cuts, likely caused by the boat’s propeller. In other cases, marine biologists must perform autopsies – meticulous autopsies similar to human autopsies – on whales to try to find the cause of death. Some autopsies this year indicated ship collision injuries, while other animals were too decomposed by the time they reached shore to be autopsied.

Of the 178 humpback whale deaths investigated by NOAA as part of an unusual occurrence, about half were autopsied. “Of the whales examined, about 40% had evidence of human interaction, whether it was ship collision or entanglement,” NOAA’s Lauren Gaches said at a Jan. 18 press conference.

Unusual winds, tidal patterns and ocean currents can increase the chance of whales stranding, and such changes may be exacerbated by climate change.

The unusually high mortality is blamed by some on noise generated by offshore wind turbine surveying equipment, although NOAA says there is no evidence to support claims that such noise interferes with whales’ ability to navigate and communicate. “There are no known links between any offshore wind activity and stranding of whales, regardless of species,” said Benjamin Lowes of NOAA at a January 18 press briefing. Protesters have recently called on New Jersey government leaders to stop the spread of offshore wind until more research is done on the potential link between underwater noise and whale deaths.

Are there other explanations?

The food source for humpback whales is increasing. In New Jersey in recent years, as the commercial fishery has declined, there has recently been an increase in a small silver fish called the Atlantic menhaden. But that means humpbacks are roaming around their foraging grounds longer than usual as a result, putting them on the path of the main shipping route. “Their food is here, and so are they,” says Dean. Part of the solution may be to change the time, place and speed of ships.

Another explanation for the surge in stranded whales could be that some species are recovering from the brink of extinction, resulting in an increase in the total number of strandings. Whaling bans and fishing regulations have allowed humpback whales to swell from around 400 individuals in the 1980s to over 80,000 today – a dramatic recovery, but before whaling their numbers are still smaller.

Sign up for Wild Wild Life’s free monthly newsletter on the diversity and science of animals, plants and other weird and wonderful creatures on Earth.