Climatic elements can influence reproduction of mammals. In temperate zones, reproduction often is related to favorable environmental factors, such as spring and rainy seasons, which correspond to availability of food. The goal of this study was to describe the reproductive cycle of the black-tailed jackrabbit, Lepus californicus, with regards to temperature, rainfall, evaporation, and photoperiod in the Mapimí Biosphere Reserve in the central Chihuahuan Desert, Durango, Mexico. If the onset of breeding correlates with these environmental factors, we predicted that mating should be related to total rainfall. To test this prediction, we collected 39 females and 36 males between July 1996 and November 1997 and measured and recorded reproductive condition. Weights of ovaries in females were correlated with increases in photoperiod, evaporation, rainfall, and mean monthly temperature. Increases in male testicular weight were correlated with increasing photoperiod only. We concluded that differences in responses of males and females were related to differing reproductive strategies. Females experience higher reproductive costs and probably respond to a more complex set of environmental cues to increase their reproductive success.