The females are gray and drab while the males are bluish turning to bright blue during the spring breeding season. These pupfish feed on insect larvae and other organic matter from the pond bottom. They prefer shallow pond depths, about 12 to 18 inches deep. In the winter, the fish apparently spend a dormant period buried in loose material in the pond bottom. Male fish are very territorial at this time and will attack any adult male or female fish within their small territories.
Receptive females channel the males' aggression into breeding behavior by their own responses.
The female initially turns away from the attacking male, then she turns back towards him, nipping at the bottom of the pond as she approaches. The mating pair disappears into the vegetation in the pond bottom, where a single egg is deposited. The territorial behavior of the males decreases as the season progresses, and the breeding season finally ends in August. By this time the males have lost their intensity of color and many of the fish have moved into the deeper, cooler areas of the pond. Current research at Quitobaquito includes population monitoring of the pupfish and investigations into the effects of nearby agricultural activity in Mexico on the pond habitat.