Optimal hunting group size: lions defending kills against hyenas

Cooper examined why lions live in groups by testing whether larger groups better retain their kills against kleptoparasitic spotted hyenas. Observations showed that single or paired lions frequently lost carcasses to mobbing hyenas, whereas larger groups defended kills more successfully, reframing optimal group size as a function of competition and food defense rather than hunting efficiency alone. The study quantified loss rates by lion group size and hyena numbers, demonstrating that the threat of kleptoparasitism can favor sociality. It is a key reference linking intraguild competition to social evolution in big cats and a classic example of how scavenging pressure from a dominant competitor shapes a predator's behavior and grouping.