Small groups and territorial males
Both the Plains and Mountain Zebras live in small family groups while the Grévy’s Zebra leads a less social life with stallions establishing territories and then mating with receptive mares that enter their territories.
At Rietvlei Nature Reserve I have observed that herds typically consist of 7 to 12 individuals with 9 being the most common number. These family groups are led by a dominant mare, a few other mares and their foals, and a stallion.
The dominant mare leads the group and there is a strict hierarchy amongst the rest of the herd who tend to follow her one by one. I witnessed a family group of 8 walking along a path and photographed them in sequence. They then mingled with another group for 5 minutes or so before heading off in exactly the same sequence. The stallion is typically found towards the back as one of his roles is to defend the mares and foals.