Threats allow individuals to modify the behaviour of potential competitors without incurring the costs and risks associated with escalated fights (Maynard Smith, 1974) but are only likely to be effective where threatening individuals have the capacity to inflict costs on others sufficiently large to inhibit their behaviour (Parker, 1974; Andersson, 1980; Cant & Johnstone, 2009). In many societies, dominant individuals also punish subordinates that infringe their interests, inflicting fitness this website costs that

offset the benefits of repeating the same behaviour. Where there are large asymmetries in power or dominance rank between individuals, the costs of punishing are often very low while costs inflicted on victims can be extremely high so that punishment is likely to be an evolutionary stable strategy (Clutton-Brock & Parker, 1995a). Punishing tactics may be used to reduce the incidence of feeding competition by subordinates, to constrain their access to social partners or to coerce them into cooperative behaviour (Hauser, 1992; Reeve, 1992). Subordinates see more that repeatedly infringe the interests of the same dominant individual may receive progressively larger punishments and may, eventually, be evicted from the group or even killed (Clutton-Brock & Parker, 1995a). However, while anecdotal examples of punishment are common,

experimental evidence of the benefits of punishing tactics to the punisher are rare in wild animals. One of the few examples of the consequences of punishment yet available is provided by experiments with cleaner wrasse, which involved presenting a dominant Urease and a subordinate with a choice of two foods, one preferred and one less preferred, which were immediately reversed if the subordinate

began feeding on the preferred food (Raihani, Grutter & Bshary, 2010). After repeated trials, dominants learned to attack subordinates if they began to eat the preferred food and subordinates learned to avoid this choice. The fact that fish are capable of learning to avoid choices that incur punishment by dominants suggests most mammals are likely to be capable of similar learning processes and that punishing tactics are often likely to increase the fitness of dominants. Conflicts of interest between group members also lead to regular harassment. For example, where two females are competing for divisible resources, repeated attempts to gain access by subordinate competitors may eventually raise the costs of continued defence to dominants until they reach a point where the net benefits of maintaining exclusive access are lower than the costs of defence. Situations of this kind resemble a ‘war of attrition’ where the winner is the individual that can afford to persist for the longest time (Clutton-Brock & Parker, 1995b). Persistent harassment can occur in a variety of circumstances.