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Humpback whale bumps have marine biologists stumped

An acne-like condition on their skin has researchers worried

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1:56pm, March 26, 2018
humpback whale

Humpback whales are looking thinner and bumpier than they used to.

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Off the Kohala coast on the Big Island of Hawaii, Christine Gabriele spots whale 875. The familiar propeller scar on its left side and the shape of its dorsal fin are like a telltale fingerprint. Gabriele, a marine biologist with the Hawaii Marine Mammal Consortium, confirms the whale’s identity against her extensive photo catalog. Both Gabriele and this male humpback have migrated to this Pacific Island from Southeastern Alaska.

In those Alaska summer feeding grounds, Gabriele sees the same 300 or so whales “again and again.” But winter brings more than 10,000 whales to the waters of Hawaii from all over the North Pacific. Spotting 875 is like finding a needle in a haystack.

Gabriele is here today to focus on the slew of worrisome bumps on the familiar traveler’s flank. The bumps are separate from the usual ones bulging from the head of a humpback (Megaptera novaeangliae). Those iconic oversize hair follicles are thought to be part of the sensory system. The smaller body bumps look more like bad acne or an allergic reaction. Noted on rare occasions in the 1970s, the condition called nodular dermatitis has become much more prevalent. These days, Gabriele and colleagues see these skin lesions on over 75 percent of Hawaii’s humpback visitors.

The bumps coincide with other suggestions of declining health in the whales. In the nearly three decades that Gabriele has been studying whales, she would not describe the animals as skinny. Now, often “you can see their shoulder blades,” she says. “They look angular rather than round.”

Gabriele’s team is trying to figure out the cause of the bumps, comparing tissue samples from bumpy and nonbumpy whales. Several times per week, a small team sets out on the water, research permits in hand. Once a whale pod is spotted, Gabriele’s colleague Suzanne Yin zooms in with a camera and volunteer Kim New enlarges the image on her iPad, examining skin on the whale’s flanks and behind the blowhole to confirm if it’s bumpy or not. Gabriele carefully steers the boat so that Yin can shoot a biopsy dart from a crossbow.

The dart “takes a little plug of skin and blubber … about the size of a pencil eraser,” Gabriele says. The dart bounces off the whale and floats until the researchers can grab it. When darted, some whales dive; others show no reaction at all.

Collaborators from the National Institute of Standards and Technology’s Hollings Marine Laboratory in Charleston, S.C., are analyzing the skin for trace elements. National Marine Fisheries Service lab staff are studying the blubber for organic pollutants like PCBs and flame retardants. Preliminary results suggest that bumpy whales differ from nonbumpy in levels of manganese and a few other trace elements. Gabriele eagerly awaits the full analyses to make sense of what she’s seeing among the migratory creatures.

Citations
Further Reading

S. Milius. Whales feast when hatchers release salmon. Science News Online. July 11, 2017.

S. Milius. ‘Whalecopter’ drone swoops in for a shot and a shower. Science News. Vol. 188, No. 9, October 31, 2015, p. 32.

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