Why lions form groups: food is not enough

Two Panthera leo group sizes maximize foraging success during the season of prey scarcity: one female and 5-6 females. Foraging success does not vary significantly with group size when prey is abundant. Female lions live in fission-fusion social units (prides) and forage only with members of their own pride. If lion grouping patterns were primarily related to group-size-specific feeding efficiency, females in prides containing <5 females should forage alone when prey is scarce; females in larger prides should forage alone or in groups of 5-6. However, females in small prides most commonly forage in as large a group as possible, even at the expense of foraging efficiency. Females in large prides most often forage in intermediate group sizes of 4 or 5. However, mothers keep their cubs in a creche and form highly stable maternity groups that are effective in defending the cubs against infanticidal males. Most large prides contain a creche involving 4 or 5 mothers; in the absence of a creche, large prides show no preference for any group size. Females also compete aggressively against neighboring prides, and larger groups successfully repel smaller ones in territorial disputes. Small prides appear to be excessively gregarious in order to compete against larger neighboring prides. "