December 15, 2018
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Mama bear’s family tree numbers 105 descendants

BANGOR, Maine — Randy Cross still can remember the second time he found himself face to face with the special bear biologists alternately nicknamed “Sara” and “The Pinnacle Bear.”

Cross, now a biologist for the Maine Department of Inland Fisheries and Wildlife, was being introduced to bear research in 1983 and was in the woods to try to see how Sara, a bear the crew visited in her den just months before, and her three cubs were faring.

While perched on the side of a small, steep mountain — The Pinnacle — Cross was joined by the bear, which put its front paws on a flat spot just 5 feet below him.

“It was better than any Disney movie you’ve seen. It was real big-screen stuff,” Cross said recently. “I thought, ‘I could almost reach out and touch her.’”

Then, after slowly turning her head, she was gone, a vacuum of beech leaves sucked behind her as she bolted away.

“That was one of my early experiences,” Cross said. “Eye opening at the time.”

In the 32 years since, Cross has had plenty of opportunities to think about Sara. In fact, the longtime biologist, who has devoted his life’s work to studying the state’s bears, said she was a one-of-a-kind animal.

Cross didn’t know it at the time, but on that early May day, he encountered the matriarch of the state’s Spectacle Pond research area west of Ashland. And because of annual research, he knows at least 105 other bears can trace their lineage through her.

Among those, 15 of Sara’s female descendants have been collared and are being studied by state biologists.

To Cross, that number is astounding. He hasn’t seen anything like it in more than three decades of research.

“This is not what you’d expect from bears, because this kind of success, if it was widespread, we’d be overrun with bears,” Cross said. “One bear in 35 years turns into 16 females (that are then studied by biologists)? That would be a tremendous rate of (population) increase.”

But that’s exactly what Sara did — produced a bloodline that is the most prolific of any of the state’s study animals. Today, Cross can trace Sara’s line through six generations. One of her granddaughters, Josie, recently gave birth to a single cub at the age of 26 — another record.

Want to know the reason for the success of that band of bears? Well, you might be surprised.

Cross said nurture — not nature — is likely most responsible for the state’s biggest documented band of related bears.

A story worth sharing

While recovering from an Achilles tendon injury this winter, Cross decided to sit down and tell Sara’s tale. The DIF&W shared it with subscribers to its monthly report last week, and it also has appeared in a department blog.

The numbers his report includes are stunning.

Sara was first captured in 1980 — the 225th bear “enlisted” into the state’s research project. She produced 11 cubs, 18 grandcubs, 32 great-grandcubs, 31 great-great-grandcubs and 13 great-great-great-grandcubs.

“Overall, 105 different bears have been tagged that are direct descendants of Sara, representing six generations of bears,” Cross wrote in his report. “Unlike males, who instinctively will roam many miles from where they were raised, females reside very close to where they were born. All of the females in this family live within a few miles of where Sara was first captured back in 1980.”

Sara died in 1987 at the age of 15. Her first three documented cubs — Clara, Belle and Karen — were born in 1983, tagged and as yearlings were fitted with radio collars that allowed biologists to visit them each winter to learn how many cubs they had.

One of Belle’s cubs was Josie, another “star” of the research project.

“This bear, the granddaughter of Sara, has provided 26 years of reproductive information for the next 26 years of her life,” Cross wrote. “By the time she was in her teens, Josie grew to become the largest female bear in the study area. The biologists were able to document 11 of her litters, including one male this winter [in 2015].”

Cross said more than 3,000 bears have been handled since Sara was first captured, but there’s not another extended brood like hers.

Why are Sara’s bears special?

The family trees of most bears in the state study are fairly short. Some barely get started before a branch on the tree breaks off.

Sara’s tree continues to flourish. But why?

Cross has spent a long time thinking about that, and he thinks he has the answer.

First, though, he has had to eliminate other potential explanations.

Do Sara’s bears tend to produce more females, which, therefore, end up in the study more often because males are fitted with ear tags but are not radio collared?

No, Cross said, pointing out that her litters and those of her daughters are perfectly average in that regard.

Do Sara’s bears simply produce more cubs than other bears? Again, the answer is no.

Maybe those cubs do better at surviving the first years of their lives — the period during which Cross said about 30 percent of bears end up dying.

Again, that’s not the case.

“All of those things are not the reason,” Cross said. “So what is left is the fact that many of these bears live a long time. That is the only thing that separates this group from other groups. And what allows this group of bears to live a long time … is how they behave and how they operate.”

Cross said he has heard some people suggest the longevity of Sara’s bears is just a coincidence. He doesn’t think so.

“Something’s happening here that’s not happening with the other bears,” he said. “And what it boils down to, if you eliminate all the other possibilities, is that these bears avoid humans more than the average bear. That’s how they live a long time.”

Part of that may be genetic, Cross conceded. Some bears simply are born more cautious. But after those genetics are diluted for six generations and the same human-averse behavior continues, he thinks there’s another, more powerful factor at work.

“The part of the picture that I think is the most influential here is that there is are behavior patterns that are set up by a female and taught to her offspring,” Cross said.

Simply put, Sara’s bears were raised right and have continued to teach the matriarch’s lessons for decades.

Doubt it? Cross doesn’t.

Consider all those male descendants roaming the north woods, looking for their own territory: It’s not too far from the study area to Ashland or Garfield or Oxbow, Cross said. The females may stay put, but the males don’t. In fact, it’s an easy walk to town for a young bear on the prowl.

“If they didn’t have a strongly developed human-avoidance behavior through their raising … then we would probably be some of these bears causing some problems,” Cross said. “We never have. Ever. None of these bears [which are identifiable by their ear tags and a lip tattoo] have ever been implicated as a nuisance animal, anywhere.”

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