The bongo is one of the least-studied of the Tragelaphini. In a study of five captive bongo calves, two males and three females, we measured several behaviors important to parental investment theory (Clutton-Brock et al., 1982), in order to describe their pattern in a rare species, and add to the database pertaining to sex allocation theory. Variations in individual patterns of maternal investment, such as suckling rate and bout length, were measured and graphed over time, with sex of calf, and age and dominance of dam indicated. Instances of "thief suckling" by calves and juveniles were also described in terms of kinship among the animals involved. Only one measure of maternal investment was biased in favor of males, which had a somewhat higher birth weight than females. Other measures showed little sex difference. Among these calves, maternal care appeared to vary more with dominance and age of the dam than with sex of calf. Data from these animals generally conform more closely to those of Byers and Moodie (1990). They found little evidence of sex-biased investment among pronghorn (Antilocapra americana) fawns, and postulated that many ungulates have such a high rate of development that further differential investment is impossible. Robust biological theories are supported by data obtained from a wide variety of species, many of which are impossible to study closely in the wild. Additional studies on captive populations of sexually dimorphic species would contribute usefully to the accumulation of data pertinent to parental investment theory.