The Pecos pupfish is well-adapted to survive in the often harsh conditions found in its habitat; not only can it tolerate a range of salinities and temperatures (6), but it is also omnivorous and will consume a variety of foods such as algae, aquatic plants and insects (7).
The Pecos pupfish’s breeding season occurs from May to September, peaking around May and June (2) (6). The breeding males establish territories, which they aggressively defend from rival males as well as from other species. The best territories consist of plants and algae for the male to feed on, as well as an area of bare rock on which the female’s eggs can be deposited. These are, however, in short supply and fiercely competed for, hence many of the smaller males do not attempt to establish a territory, and retain their non-breeding colouration. Over the course of the breeding season, the female Pecos pupfish breeds with multiple partners, selecting the largest, most vividly coloured males. After mating, the female deposits a mass of eggs, which are left with the male to defend against predation, while the female searches for another mate (4). Pecos pupfish usually only live for a year, and each year’s breeding population is therefore composed of fish born in the previous summer (6).