Young Risso’s dolphin should be named Lucky

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Risso’s dolphin photographed in April by ©Kate Cummings/Blue Ocean Whale Watch

A juvenile Risso’s dolphin photographed Thursday in Monterey Bay, California, appears to be one extremely lucky mammal.

Everett Robinson, a naturalist for Monterey Bay Whale Watch, was not aware of what look like multiple teeth marks on the dolphin, until he downloaded his images.

The image was shared on Facebook, sparking a debate about what type of predator might have tried making a meal out of the Risso’s dolphin, and where and when the attack might have occurred.

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Risso’s dolphin photographed Thursday by ©Everett Robinson/Monterey Bay Whale Watch

Great white shark and killer whale were the obvious choices, although false killer whale and pilot whale were also named as possible culprits.

A few suggested the wounds were caused by a boat propeller, but that would not explain the nearly symmetrical marks on both sides of the dolphin. Another theory was that the dolphin somehow got caught between two propellers on a twin-prop boat. Yet another was that a steel trawl net might have caused the injuries.

It’s not the first sighting of this dolphin. After seeing Robinson’s images, Kate Cummings, owner and naturalist for Blue Ocean Whale Watch, shared her images of the same Risso’s dolphin. Her images were captured in April, also in Monterey Bay.

That implies, at least, that the attack–if it was, indeed, an attack–occurred in or near the sprawling bay. The scars are completely healed, which suggests that the dolphin was only a baby when it nearly became lunch. (Risso’s dolphins measure about 4 feet long at birth.)

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Risso’s dolphin photographed in April by ©Kate Cummings/Blue Ocean Whale Watch

Alisa Schulman-Janiger, a killer whale researcher, said that the long rake marks on both sides of the dolphin are most likely from a killer whale, even though the spacing seems rather wide for killer whale teeth.

“They’re widely spaced, but this animal is growing, and the scars might have stretched,” Schulman-Janiger said, adding that transient killer whales are known to prey on Risso’s dolphins and other types of dolphin. “The scars grow with the dolphin, so the actual size of these teeth were likely somewhat smaller than the scars indicate.”

On the Monterey Bay Whale Watch Facebook page, researcher Josh McInnes countered: “Those are super long rake marks. Almost looks too numerous to be orca. I have some shots of Pacific white-sided dolphins with transient rake marks. Very different.”

Adult great white sharks also feed on marine mammals, mostly seals and sea lions, and some thought the separated teeth marks could possibly have been the result of a shark bite.

However, George H. Burgess, a renowned shark expert from Florida, ruled out a shark bite after looking at the images accompanying this post. Burgess said shark teeth would have penetrated the dolphin’s flesh and left crescent-shaped scarring.

“Those aren’t shark, so they almost certainly are from a killer whale,” Burgess wrote. “One lucky Flipper!”

Said Schulman-Janiger: “Either way, this dolphin is very lucky to have gotten away. The bite mark implies that the whole animal was in the predator’s mouth, and now it appears to be thriving.”

Thriving, but most likely extremely wary in the vicinity of large predators.

–Find Pete Thomas on Facebook and Twitter

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