Roaring and numerical assessment of opponents in lions

Playback experiments on Serengeti lionesses tested whether females could judge the size of an intruding group from its roars. Researchers broadcast recordings of one versus three unfamiliar females and watched residents weigh the odds before approaching. Lionesses were far more cautious when outnumbered and approached readily only when they outnumbered the simulated intruders, demonstrating that they keep a running tally of who is present and compare it against the threat. The study is a classic demonstration of cost-benefit decision making and numerical competence in a wild carnivore, and it grounded later work on conditional cooperation, territory defence, and the social value of group size in big cats.