Bonding in hamadryas baboons (Papio hamadryas) and the effect of daily ambient temperature, female receptiveness and bacterial infection on the structure of family units was studied for six months under captive conditions. The baboons formed three group units, including bachelors, one male unit with three subunits (adult male/female, adult male/2females and adult male/3females) and mother/infant unit. The latter was excluded from the study as the number of observations for this unit was negligible. In general, bachelors' units occupied the highest percentage of observations (54%, p < 0.05), while the male/3females sub units recorded the lowest percentage of observations, 3%).  Both male/female and male/2females subunits recorded 36% and 7% of occurrence, respectively. The effect of daily ambient temperature on group composition was positively correlated with the formation of bachelors (R= 0.46) while, it was of negligible effect on the formation of other family subunits (R= -0.03). The effect of female receptiveness was positively correlated with the formation of male/3females subunits (R=0.5) but it was negligible with the formation of other units. Ambient temperature and female receptiveness affected to some degree the bonding structure of baboons. Fecal examination for bacterial infection indicated the presence of Salmonella eneritidis, Klebsiella spp and E.coli within the population with an overall bacterial prevalence of 78%. At group level the highest percentage of Salmonella and Klebsiella positive cases was recorded in male/3females subunit.