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ANCHORAGE - Three humpback whales found floating in the waters of lower Cook Inlet were probably preyed upon by transient killer whales.

However, it isn't known whether the killer whales attacked the humpbacks or came across the carcasses and fed on them.

The 30- to 40-foot-long humpbacks have the markings of killer whale predation. All three are missing their tongues and some have lost their lower jaws, pieces of their throats, or have scraped noses, said Barbara Mahoney, a biologist with the National Marine Fisheries Service.

"Definitely, there's been killer whales on these humpbacks and it's thought they were preyed upon by killer whales," she said.

A team of North Gulf Oceanic Society researchers saw a group of 11 killer whales harassing six humpbacks near islands in the northwest part of the Gulf of Alaska on July 11.

The group has the only reported transients in the area, making them suspects, Mahoney said.

Craig Matkin, director of the oceanic society, said it is somewhat surprising the dead whales are humpbacks. The transient, mammal-eating killer whales typically feed on gray or minke whales.

"We just haven't seen much predation on adult or real large juvenile humpbacks in Alaskan waters," he said.

The damage to the dead humpbacks is not enough to prove that killer whales killed them, said Dawn Kimberlin, spokeswoman for the Alaska SeaLife Center. Killer whales sometimes feed on dead humpbacks, she said.

Other explanations for the deaths include the naturally occurring and potentially fatal domoic acid, boat strikes or starvation, Kimberlin said.

There are plans to do a necropsy on at least one of the dead whales, but they are still floating in the inlet. A necropsy won't be possible until they are on land.