Gray Whale Size Shortens by 13% Since 2000, Problem Linked to Changing Food Web and Nutrition [Study]

Gray whales living and feeding in the waters off the Pacific Northwest region of the United States are undergoing an unusual biological change. According to a new study in June 2024 led by researchers from Oregon State University, the size or length of the Pacific coast gray whales has shortened over the last 20 years to 30 years. The problem has been linked to the changing food web and nutrition of the said marine mammals.

This shortened body length of some members of the gray whale species (Eschrichtius robustus) in the region can threaten their population, according to the authors of the new research paper. The findings point out that having a smaller body size for the whales can have significant repercussions in their health and reproduction. The recent discovery also highlights its potential impact on the local ecosystem, including prey-predator dynamics.

In 2021, a study led by the National Oceanic and Atmospheric Administration (NOAA) Fisheries found an alarming drop in the population of gray whales off the US West Coast. The population of E. robustus has been considered by scientists as "stable" in recent years. However, emerging evidence still shows they could still be in danger, especially amid marine pollution, climate change, and anthropogenic threats.

Gray Whale Size Shortens

Documentation of shortening gray whale body size has been published as a study in the journal Global Change Biology on June 7. According to the Oregon State University research team, over 200 Pacific coast gray whales have shortened by 13% since the year 2000. The sample population involves whales that spend the summer season feeding in the shallow waters of the Northwest US.

Highlighting potential food web and nutrition problems, the researchers identified that the natural phenomena of "upwelling" and "relaxation" are behind the issue. The paper explains that upwelling is the sweeping of nutrients from the deeper into the shallower parts of the ocean. Meanwhile, relaxation is the opposite since it retains the nutrients in shallower areas.

The movement of these nutrients means that the prey of grey whales, including plankton and other tiny organisms, become relatively less available.

Gray Whale Population Concerns

Despite having a stable number, as mentioned earlier, gray whale population is threatened by various human-induced factors. These threats include fishing gear entanglement, oil and gas development, and vessel strikes or ship collisions, according to the non-governmental organization World Wildlife Fund (WWF). Moreover, gray whales and other marine animals are also at risk from ocean warming due to the climate crisis.

The WWF specifies that the western North Pacific gray whale is facing a potential existential threat due to the mentioned anthropogenic dangers. Over the past decade, there have been reports of gray whales stranding along beaches of the Pacific Ocean. This mysterious phenomenon was also seen in other coastal areas of the US, including humpback whale stranding off the coasts of New Jersey and New York.

In January 2021, the NOAA Fisheries in its study estimated that there were approximately 6,000 fewer migrating whales during the 2020 winter; or equivalent to 21,000 whales compared with the higher 27,000 individuals back in 2016.