Cooperation and competition within coalitions of male lions: kin selection or game theory?

Male lions form cooperative coalitions which compete against other coalitions for exclusive access to female groups^1,2. This cooperation and the apparently low level of intra-coalition competition over oestrous females, have been considered to be due to the close genetic relatedness of the males in the coalition^1-4. However, we now present evidence that breeding coalitions of male lions include non-relatives much more commonly than was generally supposed, that intra-coalition competition over females is widespread and that kinship is not the primary factor determining levels of competition.