ringbok is similar to that of Thomson's gazelle. Mixed-sex herds or harems have a roughly 3:1 sex ratio; bachelor individuals are also observed. In the mat

ing season, males generally form herds and wander in search of mates. Females live with their offspring in herds, that very rarely include domi

nant males. Territorial males round up female herds that enter their territories and keep out the bachelors; mothers and juveniles may gather in nursery herds sepa

rate from harem and bachelor herds. After weaning, female juveniles stay with their mothers until the birth of their next calves, while males join bachelor groups. A study of vigilance behaviour of herds revealed that individuals on the borders of herds tend to be more cautious, and vigilance decreases with group size. Group size and distance from roads and bushes were found to have major influence on vigilance, more among the grazing springbok than among their browsing counterparts. Adults were found to be more vigilant than juveniles, and males more vigilant than females. Springbok passing through bushes tend to be more vulnerable to predator attacks as they cannot be easily alerted, and predators usually conceal themselves in bushes. Another study calculated that the time spent in vigilance by springbok on the edges of herds is roughly double that spent by those in the centre and the op