The ant species Leptothorax acervorum is found throughout the Northern hemisphere. While many populations have multiple queens, a few have only one queen that reproduces. And in those societies, queens and workers alike viciously fight for ant dominance.
Tens of thousands of years ago, the caves of central Europe were full of two species: the aptly named cave bears and cave lions. Even bigger than their modern counterparts, these ancient monsters were locked in deadly battle for survival.