The social structure, aggression level, population size, and duration of presence of these herds across species varies greatly. Bachelor herds are most often found in mammals and are especially common in the grasslands.
Impala Male
impala form small bachelor herds during both the wet and dry seasons. These bachelor herds are generally smaller than herds of females, numbering around 4 members, compared to upwards of 10. Juvenile males begin to join bachelor herds at 8 months of age. Bachelor herds may coexist with territorial males in the same area, but these individual males are always dominant above bachelor males. However, bachelor males exhibit
reciprocal grooming despite occasional aggressive interactions between bachelors.
Fur seals Male
fur seals, as a family, commonly live in bachelor herds during the non-
breeding season. During the breeding season (April–September in the
Northern Hemisphere, September–January in the
Southern Hemisphere), the size of herds greatly diminishes. In fact, it has been observed that stallions often try to prevent foals from leaving the herd. Within Cape mountain zebra bachelor herds, there is usually no
social hierarchy. Dominance is given to the more senior members of the herd and when the oldest males leave to form a breeding herd, the next oldest bachelors take on the leadership role. There is minimal intragroup aggression and no observed fighting between members for a higher social position. They then join bachelor herds, in which they spend most of the year. This hierarchy is determined by both body size and the size of the stag's
antlers, with older stags having on average larger antlers. The older stags in the herd maintain their dominance from one year to the next. Aggression within the herd is low until the stags shed their antlers, usually in early April. Intragroup clashes then increase as the females go into
estrus. Males compete with members of their own bachelor herd for the attention of the females. This is called the “
rutting season” and it lasts only a few weeks before males and females separate into their respective herds. The level of aggression within the bachelor herd then decreases substantially. ==References==