For thousands of years, the gray whales of the eastern Pacific have undertaken one of the longest annual migrations of any mammal — starting in the cold waters of the Arctic, then down past the densely populated coasts and beaches of California before finally finding refuge in the warm, shallow estuaries of Mexico’s Baja California Peninsula, only to turn around and head back north a few weeks later. Starting in December 2018, this magnificent migration took a fatal turn.
The bodies of California gray whales began washing up along the protected inlets of Baja, where gray whales come every spring to nurse their young and mate. The first to die was a young male, beached along the shore of Isla Arena, in Guerrero Negro Lagoon. Two days later, the decomposing body of a young female was found sloshing in waves along a beach in Ojo de Liebre Lagoon, just a few miles south of the first.
Then, on Jan. 4, 2019, three more young whales were found dead, all of them severely decomposed, in the same lagoon.
Scientists are now scrambling to figure out what is killing these 40-foot-long marine mammals. The “what” is anything but obvious.
Some scientists believe there may be too many whales for the population to sustain itself. Others say this explanation of “overcapacity” and “natural causes” overlooks the gantlet of hazards that grays now face — including ecosystem alteration, ship strikes, entanglement in fishing gear, plastics pollution, disease, ocean acidification and loss of kelp forests.
Then there is climate change, which is melting ice sheets in the Arctic, altering oceanic currents, warming water temperatures and potentially changing the food supply for whales and other creatures.
Researchers, however, agree on one key point: It is essential that science identify the key cause. Gray whales are a conservation success story — having survived commercial whaling and rebounded from near extinction with the help of wildlife protection laws. Their ups and downs are important indicators for the health of the oceans.
“Like other top predators, gray whales are sentinels of the North Pacific,” said Sue Moore, an affiliate professor with the Center for Ecosystem Sentinels at the University of Washington. She notes that, while their current populations are far from being imperiled, these whales could be telling us something with implications for all marine creatures, and humans too.
Read the full article in the Los Angeles Times.