The bark and twigs of woody plants are also eaten when herbs are not available. Population density is often 25-37 per ha. A dominance hierarchy is established within a colony, and territoriality is pronounced, especially by higher-ranking animals during the breeding season. Individuals warn each other of danger by thumping the hind limbs on the ground. Breeding seasons occur during the other half of the year in the introduced populations of the Southern Hemisphere.
Females enter estrus just a few hours after giving birth and soon mate again.
They thus have the potential to bear 5-7 litters and more than 30 individual young each year. At least in northern regions, however, environmental conditions, population pressures, and social factors seem to stimulate controls that restrict the average annual production per female to only 10-12 young. At least 60 percent of all pregnancies are aborted, and the embryos are resorbed by the mother's body. In successful pregnancies the young are born in a newly constructed den lined with vegetation and well removed from the main burrow of the colony. They open their eyes after 10 days, leave the nest after 3 weeks, and are weaned at 4 weeks.