daily activities involve feeding. Their temporal activity rhythms are related to environmental factors. Light, precipitation, and temperature have positive effects on annual activities, while darkness and relative humidity have negative effects. The daily activity of maras is unimodal in winter and biomodal in other seasons. Their preferred temperature is around . Females spend more time feeding than the males, due to the demands of gestation and lactation. Males spend most of the day sitting and being vigilant for predators. Predators of maras, particularly the young, are felids, grisons, foxes, and birds of prey. Maras are also hosts for parasites such as the nematode worm Wellcomia dolichotis. Social behavior and reproduction Their social organizations have a unique combination of monogamy and communal breeding. Being monogamous, pairs of maras stay together for life, with replacement of partners only occurring after one's death. The male has almost the sole responsibility in maintaining the pair by following the female wherever she goes. A male marks his female with urine and marks the ground around her with secretions from his glands and with feces, making the grounds around the female a mobile territory. Pairs breed together alone or with other pairs in warrens shared by up to 29 pairs. Maras breed, at least in southern Argentina, from August to January. Gestation lasts 100 days in wild. Most births in Patagonia occur between September and October, which is before the summer dry season and after the winter rains. Females produce one litter each year in the wild, but can produce as many as four litters a year in captivity. Young can walk almost immediately postpartum. Dens are dug during the breeding season for the young to be raised. Litters from one to 22 pairs are grouped together in these dens. Communal living provides protection from predators with the survival rate for young being higher in larger groups than in smaller groups. One pair visits the den at a time for around one hour and the other parents circle around the den. One or two pups are nursed at a time by a female. A female may sometimes nurse a young from another pair. While a female may prevent young other than her own from nursing her, some young are able to steal milk. Mothers do not actively cooperate in raising their young. For the first three weeks, young remain near the den. At this time, distance