Red acouchies were observed in French Guiana, and compared with agoutis. Acouchies frequent all forest habitats except disturbed areas. Strictly diurnal, they show most activity in early morning. Males prefer open forests, females closed habitats. The size of home ranges and the level of activity decrease in the dry season when food resources are at a minimum. The social unit is the family, one male and one female with juveniles. Family units are separated from each other. Each individual occupies a small home range which has several much‐frequented areas and many resting places, often located in hollow logs and consisting of one nest in use and several old leafheaps. There are no food reserves in the nest: fruits are buried over the whole home range. Within each social unit, every individual mainly lives alone and home ranges have little overlap. The percentage of males decreases from the juvenile to the adult stage. Populations show large year to year density variations. The red acouchy is not similar to the agouti, but instead represents an unique adaptation among the terrestrial forest herbivore