In social animals, the alpha is the individual in the community with the highest rank. Male or female individuals or both can be alphas, depending on their species. Where one male and one female fulfill this role, they are referred to as the alpha pair. Other animals in the same social group may exhibit deference or other symbolic signs of respect particular to their species towards the alpha or alphas. In hierarchical social animals, alphas usually gain preferential access to food and other desirable items or activities, though the extent of this social effect varies widely by species. Male and/or female alphas may gain preferential access to sex or mates, and in some species only alphas or an alpha pair is permitted to reproduce. Alphas may achieve their status by means of superior physical prowess and/or through social efforts and building alliances within the group. The position of alpha also changes in some species, usually through a physical fight between a dominant and subordinate animal. Such fights may or may not be to the death, with relevant behavior varying between circumstance and species.