Little is known about the role of photoperiod in the control of reproduction in mammals from the tropics in general and, in particular, from the Afrotropics. The present study examined the reproductive photosensitivity of the pouched mouse (Saccostomus campestris: Cricetidae), a small, seasonally breeding rodent that occurs from about 12 degrees S to 33 degrees S in Africa. Groups of 10 laboratory-bred male pouched mice were exposed to either long-day (16L:8D) or short-day (8L:16D) conditions for 14 wk, after which they were killed and the spermatogenic activity of the testes was assessed histologically. A group of 10 adult, multiparous females were exposed to long-day conditions for 3 mo, after which the lengths of five consecutive estrous cycles were measured. Thereafter, day length was reduced to 10L:14D, and after 16 days acclimation, the lengths of five estrous cycles were measured. Finally, day length was reduced to 8L:16D, and after 33 days, the lengths of five estrous cycles were measured. Day length had no influence on body size, testis size, or the histology of the testis, and all specimens were actively producing spermatozoa. The length of the estrous cycle (4.0 +/- 0.3 days under long-day conditions) did not change significantly with the decrease in photoperiod. In a third experiment, 14 multiparous and six nulliparous females that had been maintained under short-day conditions for 33 days were mated and successfully reared litters.(ABSTRACT TRUNCATED AT 250 WORDS)