When looking for a spot to hibernate, ancient cave bears stuck with family.

Cave bears (Ursus spelaeus) went extinct 24,000 years ago, whereas the related brown bears (Ursus arctos) still thrive. To explain these differing fates, a team led by Gloria Fortes and Axel Barlow at the University of Potsdam, Germany, obtained mitochondrial genomes of 31 cave bears and 15 ancient brown bears from caves in Spain. Cave bears from the same caves tended to share mitochondrial DNA, which is inherited maternally, whereas brown-bear caves contained multiple maternal lines.

These patterns suggest that cave bears nearly always hibernated in their native caves, which may have contributed to their demise in the face of competition from other bears, the scientists say.

Mol. Ecol. http://doi.org/bpgr (2016)