Denizens of the Deep Do Battle

Saturday, July 19, 2003
AUSTRALIA -- Bites in the animal kingdom don't get much bigger than this.

Huge chunks taken from an 8m whale shark on the Ningaloo Reef have shown for the first time that the threatened giants has a ruthless enemy in their midst.

The culprit is not known but fingers have been pointed at a lone male orca sighted several times recently during the whale shark season.

Orcas, also known as killer whales, are rarely seen at Ningaloo Reef, which is more famous for its whale sharks, manta rays and humpback whales.

Although wild orcas have never attacked people, they are a top ocean predator and few creatures have the strength to bite through the whale shark's 15cm thick skin.

It is understood orcas have killed whale sharks off the Mexican coast.

Robin Baird, a world leader in killer whale research who is based in the United States, said male orcas could grow up to 7m and sometimes preyed on whales up to 18m.

"There's no reason why they shouldn't feed on whale sharks," he said.

"If you look at large whales that have been attacked by killer whales and got away - but suffering from big bites - they seem to be covered by tooth-rakes.

"You see a series of four, five or six linear bites where they have grabbed, but nothing has ripped off."

Exmouth tourism identity Lyn Martin was certain the killer whale, which he had seen three times in the past few years, was responsible.

"There was a strip of flesh ripped down its (the whale shark's) side and possibly on its nose," he said.

"A tiger shark doesn't have a clean bite - they rip and tear and just can't take a clean bite like that. It's a big scallop bite like orcas have."

Whale shark numbers had dropped dramatically in the two weeks when the orca was sighted on the reef. But the whale sharks returned after the orca appeared to have left.

Photographer Steve Gibson, a leading guide, said the whale shark he photographed was the first he had seen with a wound that clearly was not inflicted by a boat.