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Wednesday, September 17, 2014         

OCEAN WATCH


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Report on remoras generates apt responses from readers

By Susan Scott

POSTED:



Two emails I received referred to my recent column about remoras. Star-Advertiser entertainment reporter John Berger informed me (kindly) that my claim that ancient Romans blamed remoras for Emperor Caligula's death at sea was incorrect. He wrote, "The historical record shows that Caligula was in Rome … when he was assassinated in the year 41 A.D."

John is right; Caligula was indeed murdered in the city.

Remoras, however, do have a place among the legends of ancient Rome. Author Pliny the Younger (A.D. 61-112) wrote that Mark Antony lost the battle of Actium because remoras slowed his ships (not so). In Latin the word "remora" means delay, and the largest remora's scientific name, Echeneis, comes from the Greek "echein" (to hold) and "naus" (a ship).

My Caligula/remora mistake came from a website called Animal Diversity Web, posted by the University of Michigan's Museum of Zoology. At the end is a disclaimer I missed: Content written for and by college students. Oops. Included is a place to report errors. Done.

The other thoughtful remora email I received came from University of Hawaii marine biologist Kim Holland, who wrote that for him, whale researcher Robin Baird's hypothesis that spinner dolphins spin to remove clinging remoras "doesn't add up."

Kim wrote, "If, in fact, remora removal was behind the spinning behavior of spinner dolphins, why don't we see this behavior in all the other species of dolphins, whales, marlins and sharks that carry remoras? And, in the specific case of spinners, why does their spinning behavior only peak at certain times of the day?"

Kim speculates that spinners' spinning is more likely a social phenomenon.

THE LATE KEN NORRIS, a world expert on spinner dolphins, believed both theories have merit. Spinning sends messages to pod members as well as possibly being attempts to remove remoras.

Regarding his studies of spinner dolphins in the Big Island's Kealakekua Bay, Norris wrote in "Dolphin Days: The Life and Times of Spinner Dolphins" (Norton, 1980) that "spins (and other aerial displays) are probably used by dolphins … to mark the dimensions of the school." The sounds dolphins create during their leaps and spins communicate to every dolphin where the jumpers are in the pod, even in the dark.

Norris also noted that "some spins seem involved with remoras." About 30 percent of the dolphins his team photographed spinning had remoras stuck to them.

That was with 1970s photo technology. Baird and his team today use digital cameras with high-speed motor drives and high resolution.

Baird wrote me that of the approximately 10 spinner dolphins his team photographed spinning last year, all had remoras. It's possible, though, he added, that dolphins with remoras make multiple spins rather than just one or two, thus giving the researchers time to take photos.

Each dolphin and whale species likely has its own purposes in breaching, slapping, leaping and lobbing. Some theories are that the animal is advertising its size, competing for mates, looking at boats, relieving an itch, playing or — my favorite — releasing excess exuberance.

Since these creatures can't tell us the reasons for their acrobatics, we humans can only watch, speculate and keep open minds. Only the whales and dolphins know for sure.

I appreciate help from readers in getting my facts right, especially when the notes are sent with aloha, as these were. Thanks.

———

Susan Scott can be reached at www.susanscott.net.






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