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HJ: “And this has now involved groups all around the world trying to understand what happened, how it could happen.”

When bears emerge from their dens with three or four newborns in tow, there’s often one bear that’s smaller than the others: the so-called runt of the litter. But at Washington State University’s Bear Center, a surprising discovery is pointing to a new explanation for this phenomenon. Welcome to Pulse of the Planet’s Science Diaries, a glimpse of the world of science from the inside. Oakley, a resident grizzly at the Bear Center, gave birth to twins. And seventeen days later, she delivered a third cub. It’s the first documented case in bears of what scientists call a split parturition. Researcher Heiko Jansen explains.

HJ: If we had more bears and more facilities, we could actually do more of this and observe, perhaps, similar occurrences in other bears, but, as it stands now, it’s a one time observation. But it might fit in what others have seen in the wild: multiple cubs, one being smaller than the other. They may not just be runts who are being out competed. They may actually be gestationally of a different age than their littermates. Here’s a female who’s maybe 4- or 500 pounds giving birth to a cub that may weigh a pound. And so, the actual process of birthing itself may not be that traumatic. And so, perhaps it’s possible that one developing fetus could actually survive that process to develop a little bit longer.”

Scientists worldwide are debating possible causes for this belated birth, and how frequently the phenomenon may occur in the wild. On our website, you can check out a link to the surveillance video that’s got bear researchers talking. That’s at pulseplanet.com.

Pulse of the Planet’s Science Diaries are made possible by the National Science Foundation. I’m Jim Metzner.