'Stubborn' Elephant Seal Over 500 Pounds Keeps Trying to Cross Busy California Highway

— -- Why did the elephant seal cross the road?

That's the question officials are asking after trying to corral a "stubborn" elephant seal that repeatedly tried crossing a major highway in northern California on Monday despite being guided back to a bay multiple times, according to Laura Sherr, a public relations specialist for The Marine Mammal Center (TMMC) based in Sausalito, California.

TMMC rescue crews were continuing to monitor the seal, who appeared to be "healthy" with no injuries, early this morning, Sherr told ABC News.

The massive mammal, estimated to be anywhere between 500 to 1,300 pounds, was first reported trying to climb the divider wall of Highway 37 near Sears Point in Sonoma County around 1 p.m. on Monday, Sherr said.

TMCC rescue team members and California Highway Patrol (CHP) officers tried to help the seal into the water, but she kept coming back to the roadway, Sherr said.

The determined seal caused a mile-long traffic jam in both directions of the highway, CHP Officer Andrew Barclay told ABC station KGO.

"What we've seen is she's obviously still trying to get out of the water," Barclay said. "She's very adamant she's going to cross this stretch of roadway."

Helpers left the area late Monday evening after the seal went back to the San Pablo Bay when the tide was lower. The CHP said on Twitter that it hoped the low tide would stop the seal from returning to land.

The CHP added that units would continue to check the area to make sure the seal was OK.