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A Mysterious Ocean ‘Blob’ Might Have Kept Female Whales From Getting Pregnant

Scientists believe the blob gives us a grim look at how climate change could affect whales.

by Sarah Emerson
Mar 20 2019, 4:39pm

Humpback whale and her calf. Image: NOAA

The “blob,” a mysterious mass of warm water that stretched hundreds of miles across the Pacific for six years, may have caused fewer humpback whales to be born, according to a new study.

Between 2017 and 2018, unknown circumstances seem to have hampered humpback whale birth rates, scientists with the Keiki Kohola Project and California State University said in a study published to Royal Society Open Science on Monday—and can likely be traced to the persistence of the blob.

Scientists noticed that, in 2013 and 2014, a mother whale and her calf could be found every three kilometers of ocean.

But when they returned in 2017 and 2018, “we had to cover more than 12 [kilometers], on average, to see a mom and a calf,” Rachel Cartwright, a behavioral ecologist at California State University and lead author of the study, told National Geographic.

So what does this have to do with the strange phenomenon known as the blob?

When the blob first hit in 2013, it appeared as a massive patch of relatively warmer water in the Gulf of Alaska, roughly one-third the size of the contiguous United States and 300-feet deep, according to the estimates of Nick Bond, a climate scientist at the University of Washington who nicknamed the anomaly after the 1950s horror movie.

As it drifted south, the blob doubled in size, covering 4 million square kilometers and raising temperatures 2.5 degrees Celsius above the norm in some areas. In 2016, National Geographic described it as cooking the Pacific, and mass die-offs of marine life, all along the food chain, were reported at the time.

The team scoured the ʻAuʻau Channel near Maui and Lanai in Hawaii for humpback mothers and their calves—hunting for footprints, “a vortex of flattened water” created as the animals dive—as some females travel 3,000 miles in the summer to rear their young off the islands.

They believe that disruptions to the whales’ food chain resulting from the blob may have caused female humpbacks to stop ovulating. A certain amount of hormone-triggering body fat is “a requirement for both the initiation and successful maintenance of reproduction,” the study notes. And without it, females may have stopped breeding and traveling to Hawaii.

Other studies found similar trends, National Geographic pointed out, and not only in Hawaiian waters but near Alaska, too.

Such possible findings should be treated an analog for climate change, showing how it could devastate the ocean’s equilibrium, the study says. Experts have warned that, if global warming persists, events like the blob will become the new normal.

The study also concedes, however, that mother-calf pairings may have appeared to have declined because they were simply behaving more cryptically—hanging out in more remote waters, and “undetected during acoustic monitoring.”

Cartwright told National Geographic that whale numbers in Hawaii have bounced back this year, but that we shouldn’t use it as an excuse to stop caring.