Bioacoustics of Lagostomus maximus

Movements, Home range and Social organization. The Plains Viscacha is colonial and builds a communal vizcachera, where 1-3 adult males, 2—4 times as many females, and young live together throughout the year. Number of burrows is 18-93, with satellite burrows scattered among them. Satellite burrows are seldom used except to escape high-risk situations in winter; they serve as residences and display sites for adult males during the breeding season from spring to autumn. An individual Plains Viscacha generally entersits own vizcachera rather than a satellite or another principal vizcachera, unless there is extreme danger. All individuals from a single vizcachera share a common home range, averaging 1-3 ha in central Argentina, with a minimal overlap between adjacent vizcacheras. Principal vizcacheras and their associated satellites are aggregated in patches called “vizcacherales.” Individuals may forage at considerable distances beyond boundaries of home ranges. A. C. Llanos and J. A. Crespo in 1952 reported that Plains Viscachas forage up to 400 m from their vizcacheras. Boundaries are not defended, but all members of a group will defend their vizcacheras from intruders of either sex or age class. They also have frequent cooperative behaviors such as grooming and anti-predator calls. A call may be repeated continually for several minutes, is contagious among males at neighboring vizcacheras, and results in a general run to their home burrow. The Plains Viscacha is a good and speedy runner (up to 40 km/h) and can jump up to 3 m. When startled by a minor threat, adult females and occasionally juveniles give a single syllable “wank.” A group responds by looking around but does not run for cover. When under severe stress, individuals emit a “scream” that results in conspecifics running to that individual. Members of a group have access to all burrows in vizcacheras, and all members use a communal dust bath. There are no clear dominance hierarchies among males or females. Two or more resident adult males often sit in close proximity to each other near a burrow entrance, occupy the same underground chamber even during the mating season, and forage together. Males disperse, but when environmental conditions are poor, they may remain in their natal vizcachera up to 27 months. During a population decline in semiarid scrub in La Pampa Province, adult females and juveniles abandoned their resident vizcachera when number of individuals became very low and moved as a group to the closest vizcachera. Predators of Plains Viscachas include the Puma (Puma concolor), Geoffroy’s Cat (Leopardus geoffroyr), the Crab-eating Fox (Cerdocyon thous), the Pampas Fox (Lycalopex gymnocercus), the Lesser Grison (Galictis cwja), the great horned owl (Bubo virginianus), the crowned solitary eagle (Harpyhaliaetus coronatus), and the boa constrictor (Boa constrictor).

Activity patterns. The Plains Viscacha is nocturnal and active throughout the year, emerging from burrows shortly before dusk. Groups of up to 30 individuals forage together. Adult males forage with females and young in winter but alone during the rest of the year. Seasonal changes in activity budgets of males are associated with increases in conflicts among males, vigilance for intruding males, and territorial displays. Females remain their natal home ranges, but males typically disperse although they may continue to reside in their natal home ranges when environmental conditions are poor. Groups frequently coalesce and change membership during the night. Complete turnover of adult males is typical every year, with resident males replaced by immigrants from other colonies. Residents repeatedly chase intruders. Fights occur occasionally, with bipedal wrestling, biting of hindquarters and throat, rolling, and kicking. Aggression among neighbors is rare. Grooming was observed among all sex and age classes within a group and consisted of nibbling on face, neck, and back and rubbing cheeks. Mutual grooming is common. Plains Viscachas—most frequently adult males—emit loud, two-syllable “pi-chung,” anti-predator calls, which are interspersed with whinnies, grunts, squeaks, and foot stamping. These calls are similar to those used in response to male intruders. During aggressive encounters,tail is arched, and hairs are erected. Adult Plains Viscachas collect bones, stones, and sticks and pile them at entrances of vizcacheras. Adult males urinate on sticks and rub their cheeks on them; females do not show these behaviors. Tail is used as a third leg when an individualsits on its haunches. Plains Viscachas dig with their forefeet, and soil is pushed out with the nose or kicked backward by hindlegs.