In France, Brown Bears Desperately Need Women

The brown bear population has been declining in parts of France for decades, but now a group of scientists say they have an unorthodox solution. Just bring in more female bears. But not for the reasons you might think.

Normally relocating bears is frowned on as a way of saving populations. Conventional environmental science says that a declining population should not be moved until the sources of its decline have been addressed. But this group of French biologists say that in this case, they have population models that prove the cause of the decline in the population has to do with a gender disparity.

While you might think this solution is obvious, it isn't. You see, the problem with these bears isn't that there aren't enough females to breed a new population - in fact, there are. Instead, the problem comes from the bears' practice of co-rearing their young, with the fathers sticking around to care for their offspring. Because the babies take a while to mature, there will be long stretches where some males are fathers and others aren't. The single bears will fight the fathers. When single bears win, they murder the father's offspring so they can parent their own children. As a result, even a slight gender imbalance between the bears can result in viable offspring being killed over and over.

The scientists' study was published yesterday in PLoS One. A release about the study explains:

The researchers analyzed field data collected from 1993 to 2005 and found that the western sub-population had much lower reproductive success than the central sub-population. They suggest this could be the consequence of the western sub-population being inbred or having a male-biased sex ratio. In species with extended parental care, a male-biased sex ratio can induce sexually selected infanticide, a behavior in which males attempt to kill unrelated cubs to induce estrous in females, maximizing their opportunity to breed.

[Researcher Guillaume] Chapron and his colleagues used a population model to compute how many bears should be released to ensure viability, and showed the population could recover provided an adequate number of new females are translocated.

via PLoS One