Competition between females is one of the cornerstones of the theory of natural selection but the majority of studies on reproductive competition focus principally on mating competition in males. The 2013 Thomas Henry Huxley Review, published in the Journal of Zoology, provides a fascinating summary of the adaptive tactics used by competing female social mammals and the social mechanisms that affect competitive success.
The authors, Tim Clutton-Brock and Elise Huchard, explore a range of competitive strategies, including punishment and harassment, reproductive suppression, infanticide, eviction, kinship and dominance. Some intriguing elements of competition, such as female armaments and ornamentation, female masculinisation and sexual mimicry, are also described. In some species, both the extent of reproductive skew and the intensity of selection on traits that enhance competitive success are greater in females than in males. However, overt fighting between females is not as common as among males and the development of sexually selected weaponry in females is rarely as extreme as in males. Instead, females tend to use social strategies to enhance their reproductive success, which may explain why females are commonly more responsive than males to social signals and relationships. Despite the presence of these differences, the underlying mechanisms affecting fitness in the two sexes are fundamentally similar. As in males, females compete to maintain exclusive access to resources and mates as well as to attract members of the opposite sex. In recent years, the underlying similarity in the operation of selection in males and females has generated debate over whether or not reproductive competition between females should be regarded as a form of sexual selection or whether it should be allocated to some other category of selection, such as social. Whichever approach is adopted, the existence of this discussion underlines the qualitative similarity in the evolutionary mechanisms operating in both sexes.