Lagostomus maximus
plains viscacha

The plains viscacha exists in extreme southwestern Paraguay, northern and central Argentina, and southern Bolivia. (Nowak 1991)

Lagostomus maximus inhabits grasslands and lowland desert scrubs. The animal also constructs burrow systems in the barren parts of pampas at an elevation of 2,680 meters. (Nowak, 1991)

Lagostomus maximus is the largest member of the chinchilla family. Its combined head and body length measures 470-660 millimeters and its tail length is 150-200 mm. The color of the pelage of the animal is well correlated with the environment. The fur on its dorsal side is light brown in sandy areas and dark grey in regions where the soil is dark. The ventral surface is white. The tail is completely covered in fur. Guard hairs along the back of the animal are dark and coarse and contrast with the thick soft underfur. Unlike many other rodent species, L. maximus have a distinctively marked face. The head is large and blunt. Broad black and white stripes run along the animal's face. The rhinarium is furred and intricately folded. The forefoot contains four digits from which sharp stout claws extend. The amimal uses its claws for digging and its nose to push the dirt out. The hindfoot contains a pad of stiff bristles.

Lagostomus maximus exhibits strong sexual dimorphism. Males can be four times as massive as females. Both sexes have mustache-like whiskers, but this feature is much more pronounced in males.

(Branch 1994), (Nowak 1991)

The plains viscacha is a highly social mammal, living in communities of 15-30 and sometimes up to 50 members. The social group is usually composed of one to three males, three to five times as many females, and immatures. The species is known to construct remarkable community burrow systems called viscacheras, which consists of many interconnecting tunnels and chambers. A viscachera may cover up to 600 sq meters and contain 4-30 entrances, some of which are large enough to allow a person to stand waist-deep in them. A few large viscacheras are known to have existed for centuries. Satellite viscacheras located beyond the core burrow system are much smaller and are used only for temporary cover. A few entrances are active at a time; others are plugged with inedible items such as sticks, stones, bones, and other objects. Viscacheras are valuable resources for L. maximus, as they protect the members from predators and provide sanctuaries for mating, birthing and raising young. The long term social unit is the female-bonded group. Females reside in viscacheras when no males are present and continue to remain there through a series of males. Under stable conditions, closed matriarchal societies exist in which maturing females are recruited into their natal burrow systems. Females are thus permanent tenants of the viscacheras, and adult males disperse annually to different communities. Males gain access to burrow systems only through contest competition. However, natal dispersers and resident males from the previous year leave the viscacheras without contest competition with male immigrants. It has been speculated that this behavior may be an adaptation preventing males from mating with their daughters (Branch 1993). Contests among immigrant males occur six months before breeding and continue throughout the breeding season. Due to dispersal and mortality associated with competition, there is a high turn-over rate of males. The majority of scars on males are attributed to same-sex violent encounters. As a result of mate and resource competition, it is advantageous for males to gain as much physical strength and size before dispersal; males thus take longer to mature than do females.

An exception to the above matriarchal system occurs during a population crash. As the density of members decreases in a natal group, females disperse and attempt to fuse with other nearby viscachera communities. Like their male counterparts, they are required to enter contest competition with the resident females to gain residency.

Once males have successfully attached themselves to a group of resident females, they spend the rest of their tenure defending the females. Such territorial behavior is achieved by scent marking activities. Males rub sticks onto their cheeks and deposit them at burrow entrances. Feces and urine are spread nearby the surface of the entrances. In addition, males use a range of alarm vocalizations to defend members from predators. Individuals give a "wank" sound in a bipedal posture to indicate mild alarm. A high-pitched two syllable sound is the anti-predator call, which is only given when the situation is grave. Vocalizations are used by both females and males to advertise occupancy of a viscachera. Solicitations by nonresident groups provoke agonistic conflicts, in which resident males chase, bite, wrestle, and fight strangers away.

Close physical contact is tolerated among members. Allogrooming and other amicable behaviors are commonly observed among individuals of the same viscachera. Members nibble on each others necks and backs, touch noses and rub cheeks. In addition, the species also takes dust baths in depressions near viscacheras; this activity removes ectoparasites on the skin and absorb the oils on the fur. It has been suggested by Branch (1993) that this scent sharing activity is a behavioral device used to appease members and promote group cohesion and identification.

The plains viscacha is nocturnal, emerging from its burrow before dusk to feed. Femals and immatures forage in groups. Males may forage with females and immatures, but they are usually found alone. The home ranges of the groups are exclusive and are rarely found to overlap.

(Branch, 1993), (Branch, Villareal, and Fowler 1993), (Nowak 1991)

The species is herbivorous. In captivity, it consumes almost any kind of vegetation. In the wild, the animal feeds on seeds and grass, mainly Medicago minima and Erodium cicutarium. (Branch 1993), (Nowak 1991)

The species is considered to be a pest to farmers. It raids cultivated crops and construct burrows large enough to cause cattle to stumble and break bones. Although unconfirmed, there are claims that the animal's acidic urine devalues the soil for many years. Recent extirpation campaigns of L. maximus by humans have greatly reduced the population of the species. (Nowak 1991)

Lagostomus maximus has been a source of meat and fur for humans. (Nowak 1991)

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