A Society of Monogamous Crowd-Dwellers
The Patagonian mara (Dolichotis patagonum), a large rodent endemic to the arid grasslands of Argentina, has a social system that is rare among mammals. They are strictly monogamous, with pairs often bonding for life. This lifelong pairing is maintained by the male, who diligently follows the female, creating a mobile territory around her. He marks this area with urine and glandular secretions to ward off rivals.
Despite this fierce pair-bonding, maras become highly social during the breeding season from August to December. Multiple pairs, sometimes as many as 29, will share a single, large underground den, or crèche, to raise their young. This communal arrangement offers increased protection from predators like foxes and birds of prey. Studies show that the survival rate for pups is higher in these larger groups. A single den can contain an average of 4 breeding adults and their offspring.
The young maras, typically a litter of one to three, are born well-developed with their eyes open. For the first three to four weeks, they remain near the den, where they are very social, huddling and playing with the other pups. This early interaction helps them learn scents and build strength.
Distinct Parental Responsibilities
Within the communal den, parental duties are sharply divided. The male’s role is almost entirely focused on vigilance. He spends the majority of his time scanning for predators, which allows the female more time to forage to meet the high energy demands of pregnancy and lactation. Males rarely interact directly with the pups.
Females, on the other hand, manage all the direct care but their visits to the crèche are brief and infrequent. A mother visits the den only once a day for about an hour to nurse her young. When she arrives, she gives a shrill call that summons all the pups from the burrow. She then identifies her own offspring by their unique scent before leading them a short distance away to suckle. This identification is important, as females will aggressively reject attempts by other pups to steal milk. After about 13 weeks, the young are weaned and can forage with their parents. This combination of monogamy and communal denning is an adaptation to the pressures of life on the open Patagonian steppe.