The timing of reproduction of many species depends on seasonal changes in prolactin secretion. Photoperiod coincides with annual seasonal changes and typically regulates prolactin secretion. However, when environmental conditions are unpredictable, other ecological factors may contribute to prolactin regulation. In African striped mice (Rhabdomys pumilio), males show seasonal changes in reproduction and in prolactin levels, but unexpected increases of food availability out of the regular breeding season can also induce reproduction. We measured prolactin levels in free-ranging male African striped mice during three periods: (1) the natural breeding in spring with increasing photoperiod; (2) the natural nonbreeding season in summer (dry season) with decreasing photoperiod; and (3)during two summers with unexpected rainfall inducing breeding in the population. Here, we report that breeding males showed increased prolactin levels when they were breeding independently of increases and decreases in day length. Also, we found a positive correlation (P = 0.05) between the availability of food plants and prolactin levels. Changes in prolactin levels in opportunistically breeding species like the African striped mouse are not strictly regulated by photoperiod, but seem to respond to cues from food availability.