A popular grizzly bear family in Grand Teton National Park may be disbanding, leaving the mother free to mate and her three cubs to fend for themselves for the first time in almost three years.

Dubbed No. 399 by park biologists, the mother grizzly was known for using habitat near roadsides close to Jackson Lake Lodge, Willow Flats and Oxbow Bend. Since spring 2006, thousands of park visitors witnessed the bear family grubbing for food along the roadside.

Grand Teton biologists anticipated that No. 399 would encourage her cubs to leave this spring. The cubs appear almost as large as their 12-year-old, roughly 350-pound mother, though they likely weigh much less.

Sue Cedarholm, assistant to nature photographer Tom Mangelsen, traveled into Grand Teton to watch the bears every day for the past two weeks. The cubs appeared to be asserting their independence, often foraging up to 100 yards away from their mother, she said.

“One was always lollygagging back, digging and digging and digging,” she said. “One day at the Oxbow, the mom was trying to cross the road. She goes across and grunts and they completely ignore her. It took her three tries to get them across. They were like ‘Whatever, mom.’ People were joking that they were just like three teenagers.”

Then last Friday, Cedarholm said she witnessed the family behaving strangely, growling and fighting as they walked up Pacific Creek Road. “They were sort of ambling along and then they started running and nipping at each other and biting each other,” she said. “People knew there was a big boar up there.”

On Saturday morning, people witnessed No. 399 and her cubs on a hillside above Two Ocean Lake Road with what observers called “a much bigger bear” close by. Neither No. 399 nor the larger bear, presumably a male, displayed any aggression. Mother bears with young will often violently defend their cubs from male bears.

By mid-morning, a big dark bear came up out of a ravine near the hillside followed by No. 399. “They were just grazing a little,” Cedarholm said. “It was definitely a male bear because it mounted her.”

Roughly half an hour after No. 399 and the male disappeared back into the ravine, Cedarholm saw two of No. 399’s cubs walking down the hillside. “They were definitely acting nervous,” she said. “They went into a ravine, and then less than five minutes later, they came hauling ass up the hill. No. 399 was chasing them. She stopped halfway up the hill.”

Grand Teton’s senior biologist Steve Cain said the bears seem to be behaving normally.

“We’ve had reports that she’s been with two different males, which is not uncommon,” he said. “We don’t know anything about either [of the males].”

According to Cain, No. 399 had continued to nurse her three cubs, even this spring.

“It is common for them to lactate right up until they kick the cubs off,” he said. “She’s in estrus. There is another cue not related to lactating that brings them into estrus.”

Cain said the mating period will last for a few more weeks. If a male manages to mate successfully with No. 399, her fertilized eggs won’t become implanted into the uterus until next fall. This delayed implantation helps the female survive during poor food years, Cain said. If No. 399 is not nutritionally sound, the eggs won’t implant, which could help her survive the winter.

As for the cubs, Cain said this period in their lives is crucial.

“During this next year, there will be a lot to determine whether they live to be old bears or not,” he said.

One of the cubs is thought to be male and the other female, while the sex of the third is unknown. Cain said female cubs will likely stay close to their mother’s home range while male bears must disperse to find their own adult home ranges.

In the meantime, park officials will watch the cubs closely to make sure they don’t get into trouble. Park officials have already used horns and sirens to chase off one of the cubs that seems inclined to walk on the roadway and to get too close to people.

“The biggest problem that the park staff are having are visitors wanting to approach these bears too closely,” Cain said. “Or, by the same token, allowing the bears to approach them too closely. What we’re worried about is that somebody might feed them or that another type of confrontation could occur that could result in a human injury.”

People should always stay far away from bears, Cain said, and should keep extra distance between themselves and No. 399 while she is mating. The big male grizzlies that are courting No. 399 aren’t used to people, and could become aggressive defending her.

Park officials might consider collaring one or more of the cubs to help pre-empt any trouble they might get into, Cain said.

“How they behave in the next days and weeks will determine that,” he said. Capturing and relocating the cubs is another option if human conflicts occur.

“Our primary goal is to try and help these bears make a successful transition to independence and adulthood,” Cain said.

Re-collaring No. 399 is also an option. The Interagency Grizzly Bear Study Team, a group that monitors grizzly bears in Greater Yellowstone, uses radio-collared females for much of their research. Researchers have captured No. 399 several times in the past. Her last radio collar dropped off in October 2006.

Photographer Mangelsen said he hopes park researchers will refrain from collaring No. 399 or her cubs.

“I think this particular bear ought to be off-limits because she has been so wonderful – and the same with her cubs,” he said. “If she has a radio collar on her, most of us will back off from watching her now. It’s a human-handled bear.

“I’ve never seen an animal with a collar on it that looked like it was comfortable; it has to be an annoyance,” Mangelsen continued. The collaring process is dangerous, intrusive and stressful, he said.

“The information that you get from collaring oftentimes is really questionable,” he said.

Mangelsen said he’s shot between 20,000 and 25,000 pictures of the family in the last month.

“It’s one of those rare opportunities,” he said. “I’ve never seen anything like that before and I’ve been here 30 years. She’s incredibly tolerant of people, and she kind of does her own thing.”

Mangelsen said No. 399 was inordinately good mother to her cubs.

“They would run and tumble around,” he said. “They were obviously in good health when they came out of the den. It was nice to see her so interactive with her cubs. She loved to play and certainly her cubs loved it more.

“Hopefully she comes back and hopefully she has another set of cubs and does a similar thing and many more thousands of people will get to witness all of that,” he said.