Is Pollution Not Allowing Polar Bears to Mate?

A new study finds a link between chemicals and bone loss that could damage males’ penises, potentially harming reproduction.

In the Arctic, pollutants banned from the U.S. in 1979 but still floating around the environment seem to be affecting the strength of polar bear penile bones, possibly compromising the ability of the animals to reproduce.

PCBs, or polychlorinated biphenyls, were once used in everything from transformers to paint and are notorious for their ability to hitch a ride. They have been found all over the world, and they tend to hide out in whatever unlucky creatures eat them, ensconcing themselves in body fat and causing cancer and variety of other nasty effects.

Those effects, it appears, may also include damaging the baculum, a bone in the bear’s penis, scientists report in the February issue of Environmental Research.

PCBs are especially bad for animals high on the food chain: A single fish may have just a little, but seals eat many fish each day, and polar bears eat seals. Eventually, all those pollutants build up into quite a dose for larger animals. This is called biomagnification. (Watch: “State of Polar Bears.”)

“With these chemicals, you don’t see an acute toxic effect, but there are effects that are not really visible to the eye,” said Christian Sonne, a biologist at Denmark’s University of Aarhus and lead author of the study.

What Is a Baculum?

Many mammals, including cats, dogs, bats, gorillas, and hedgehogs, have a bone in their penises called a baculum. Humans are one of the few mammals without it. (Related: “A Most Interesting Bone.”)

What does a baculum do? Over the years, theories have included helping males mate for longer periods of time and inducing ovulation in females, but the current scientific stance is, “We don’t know!” says Sonne. In bears, it’s thought the bone no longer has a particular purpose.

But Sonne said that even if the bone is an evolutionary leftover, if it should somehow break, it could cause a condition in which the bear is unable to mate.

And that’s where the PCBs come in.