Shark Bite or Boat Strike?

Aug 9, 2013 gray seal
Shaving the area around Triton's wounds.
Shaving the area around Triton’s wounds.

Ever since the admission of our newest patient, Triton the grey seal, we have had a lot of questions regarding  the wounds on his body. At first, we thought these wounds were due to a shark attack, but at closer inspection, we determined that it was most likely a boat propeller that tore up poor Triton. So, how do we figure out if a seal was hit by a boat or had a close encounter with a shark?

A harbor seal with a shark bite injury. Photo courtesy of University of New England Marine Animal Rehabilitation Center.
A harbor seal with a shark bite injury. Photo courtesy of University of New England Marine Animal Rehabilitation Center.

A shark bite would show deep narrow lacerations where the teeth punctured the animal, almost like a stab wound. There would also be a half circle like pattern of punctures, consistent with the shape of a jaw of a shark. The wounds would be jagged and not smooth.

Once we shaved Triton, we discovered that the wounds were not too deep, and the lines on his body were linear and straight. They were curved in a circle like pattern, which means he was most likely struck by a spinning propeller on the back of a boat. Boat strikes often leave parallel straight lines on an animal as well. Whenever there is a clean or smooth line on an animal, it is most likely a man made object that caused the injury. The endangered manatees that live in the warmer southern waters are often the victim of boat strikes. Although we can never be 100% sure of how an animal was injured, the wounds left behind always leave us clues.

Triton's wounds are beginning to heal.
Triton’s wounds are beginning to heal.