The massive mom-to-be was finally captured at the Sonoma mud flats near Highways 37 and 121 and was then moved to Chimney Rock at Point Reyes.
PHOTOS: Elephant seal captured in Sonoma County
The 900-pound elephant seal was released in the dark in hopes of not disturbing the others on the protected beach. A male elephant seal, also called a bull, was heard lurking in the night.
"The big bulls are definitely a risk for us, they're dangerous to people, absolutely. They heard the noise. They heard the jostle. They wanted to know who it was. That was them trying to find out who was in their territory," said Laura Chapman of the Marine Mammal Center.
That elephant seal caused a huge traffic jam for more than a mile in both directions on Highway 37. As of 11 p.m. it was beached in the mud, just off the shoulder of the highway, looking either distressed or too tired to do anything after a long day of trying to cross the road. It stayed there after the tide rolled back into the San Pablo Bay.
On Monday, CHP Officer Andrew Barclay says he got a face-full of hot breath and saliva while trying corral this extremely irritated mammal.
Barclay said the elephant seal had "a lot of weight behind her and a lot of muscle. So she was moving us pretty easily, a lot of force."
The elephant seal hopped out of San Pablo Bay, around 1 p.m., scooted its way in front of eastbound Highway 37 traffic and tried to crawl over the median. Barclay and the others coaxed her back into the estuary.
The next day, marine mammal experts spent a second day preventing the determined female elephant seal from crossing Highway 37 near the Highway 121 split until she was rescued.
"Elephant seals in general are stubborn. You usually have to use twice as much pressure, or a little bit of effort, more than other animals," said Barbie Halaska of the Marine Mammal Center.
She had already crawled out onto the highway the day before, causing a huge traffic jam.
"We were able push her back in the water, and we were hoping she would go back out with the tide last night. Unfortunately, she was still here in the morning," said Marine Mammal Center director of veterinary science Shawn Johnson.
Finally, the wayward elephant seal found a culvert. She swam down the creek, under Highway 37 and plopped down in the field she was trying to reach. Marine mammal experts quickly tranquilized her and performed an ultrasound.
"We did see a fetus, so she is pregnant. It will be great to get her back out where she can have her pup on the beach where she should," said Johnson.
Rescue workers named her Tolay after the creek she swam down. Tolay is now on the beach at Point Reyes where she can avoid the traffic and have her pup, where elephant seals have been breeding for more than 150 years.
We are still on scene SR 37 E/ of SR 121 with a sea lion that wants no part of us. Rdwy clear but traffic is heavy pic.twitter.com/q2VfypMQI4— CHP Marin (@CHPMarin) December 28, 2015
She is huge! Estimated 900lbs. pic.twitter.com/lWcGH39yLz— Katie Marzullo (@KatieABC7) December 29, 2015