The largest peccary species, the Chacoan peccary was first described by Rusconi in 1930. The Chacoan peccary was first documented by Western science in 1975. It has only been reported from the Gran Chaco region of western Paraguay, northern Argentina and southeastern Bolivia. Surprisingly, this description was made from fossil remains and the peccary assumed extinct, until 1972 when Dr. Ralph Wetzel, on an expedition to the Gran Chaco, discovered three types of peccary recognized by the natives: the collared and white-lipped peccaries and a larger third species. Known locally as the tagua, this peccary is thought to be the most ancient, due to its small mental capacity and lack of adaptability.
The Chacoan peccary weighs 66 - 88 lbs. Diurnal in nature, it lives in semi-arid thorn forest in areas of low rainfall and high temperature in the driest parts of the Gran Chaco.
It lives in small stable groups of 2-10 individuals, with most groups consisting of 4 - 5 adults and accompanying juveniles.
When frightened, Chacoan peccaries flee, raising the long hairs on their back and spraying secretions from their dorsal gland, presumably to keep the group together in the dense brush via odor. These secretions are rubbed against group members, and are also used as territorial markers. The population density is calculated to be 9.24 animals per square kilometer in favourable and protected areas.