Communal breeding in the mara, Dolichotis patagonum

Mara social organization involves a combination of monogamous territoriality and co‐operative, communal breeding that has not otherwise been described among mammals. Some pairs reared their young in communal warrens, and pup survival was greater in warrens with larger memberships. Pairs visited their young once daily, and females resisted, sometimes unsuccessfully, the attempts of interloping youngsters to nurse. Stolen nursing facilitated the survival of orphans. More adults were present at larger creches, and total vigilance was thus increased despite each pair spending less time sitting‐alert and less time at the warren. The proportion of the day for which at least one pair was vigilant at the warren increased to 90% with larger creche sizes. Pups were much more likely to emerge from the warren when adults were present, and in the absence of adults were more likely to be sitting‐alert close to the entrance. These observations are compatible with hypotheses explaining the mara's social system in terms of resource dispersion, anti‐predator behaviour and thermoregulation. Copyright © 1992, Wiley Blackwell. All rights reserved