Most primates live in social groups. While group size ranges from a few to over 100 individuals (depending on species), the composition of a primate group is pretty stable. The hub of the group tends to be females with offspring. Some groups have just one male, the harem leader, who monopolizes females by chasing other males away from a territory. Other groups have multiple males, and may range over areas too large to defend. Regardless, dominance hierarchies are often established in primate groups. The strongest individuals get better access to food or other resources. Primates are constantly picking through each other's fur (grooming). While grooming removes parasites and cleans fur, it may also help maintain social hierarchies. Scientists have found that in some primate societies, subordinate females will groom dominant females in exchange for extra food.