Theory 57/Population/Group living
Group Size Balances Two Risks
The claim
Optimal group size is set by the ratio of predation risk to competition cost, so groups grow where predation is high and shrink where food is limiting.
01Mechanism
Larger groups dilute predation but increase competition; the optimum is where the two marginal costs balance.
02Prediction
Group size should track the ratio.
03Refutation
Group size tracking predation alone would remove competition.