Story highlights The dolphin is not trapped in the Huntington Beach wetland channel

Experts don't understand why he returned Saturday after seeing two other dolphins

"I've never seen that type of interaction," a marine rescue official says

Another effort to lead the dolphin out of the shallows is expected Monday

A dolphin's determination to stay in a narrow channel in Huntington Beach, California, for the past four days baffles marine experts who are closely watching the animal.

"He's not trapped in this area," said Peter Wallerstein, the program director for Southern California's Marine Animal Rescue.

The animal appeared to be healthy and in no danger Sunday, Wallerstein said.

"He's eating fish, sardines," he said. "That's a good sign." While he's "showing some signs of being disoriented," his breathing rate is a normal three breaths a minute.

The 6-foot-long common dolphin caused a stir when it first appeared in the dead-end wetland area Thursday, raising concern for his safety.

Would-be rescuers used paddle boards to coax him back into the harbor Saturday, but their efforts were reversed when two other dolphins "lingering in the harbor" appeared, he said.

"As soon as he saw them, he changed his behavior immediately and swam back under the bridge," Wallerstein said. "I've never seen that type of interaction."

It might take a dolphin psychologist to explain why the animal returned to the channel, he said. "He chose to be in here for some reason."

Another effort to lead the dolphin back into the harbor is expected Monday but with "more of a defensive stand under the bridge, so he can't get back in," he said.