Crested rats don’t just chew tree bark that’s poisonous enough to kill an elephant. The rabbit-sized rodents dribble and lick the toxic drool into their long rat fluff for a weaponized hairdo. Yet these dangerous rats, which scientists assumed were loners, turn out to have a close and cuddly family life. They even purr.

Chewing on bark or other parts of East Africa’s arrow poison trees gives the rats toxic saliva to apply to specialized zones of fur. The toxins sink in to porous, easily detached hairs on the rat’s flanks. Any predator foolish enough to bite a Lophiomys imhausi gets a hairy mouthful of bitter toxins that human poachers use on arrows for hunting big game.

The rats “have the personality of something…