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Lagostomus maximusplains viscacha

By Nghi Tran

Geographic Range

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

Habitat

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)

Physical Description

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)

  • Range mass
    2.000 to 8.000 kg
    4.41 to 17.62 lb
  • Average basal metabolic rate
    10.623 W
    AnAge

Reproduction

Lagostumus maximus is capable of breeding throughout the year in captivity. In the wild when conditions are favorable, two litters are produced annually. However, plains viscachas in east-central Argentina have a single breeding season in which mating occurs in March-April and births in July-August. The reproductive pattern of female plains viscacha is distinctive in that many ova are shed to produce only a litter of two. Sectioning of the reproductive tract by Weir (1971) established 50-845 ova released by the female. Up to seven embryos implant in the uterus of the female and development continues for 30 days. By the 90th day, all but the most caudally situated embryos in the uterine horn are resorbed.

Females have an estrous cycle of 45 days. The gestation period lasts 145-154 days. The number of individuals in a litter is usually two, but the range is one to four. When born, the young are precocial and fully furred, weighing approximately 200 grams. Females lactate for a minimum of 21 days, but the young are usually weaned after eight weeks. Females reach sexual maturity at 8.5 months and males at 15 months.

(Birney and Day-Baird 1985), (Branch 1993), (Branch, Villarreal and Fowler 1994), (Nowak 1991)

  • Key Reproductive Features
  • gonochoric/gonochoristic/dioecious (sexes separate)
  • sexual
  • Range number of offspring
    1.000 to 4.000
  • Average number of offspring
    2.000
  • Average number of offspring
    2
    AnAge
  • Range gestation period
    145 to 166 days
  • Average gestation period
    153.7 days
  • Range weaning age
    54.000 (high) days
  • Average age at sexual or reproductive maturity (female)
    Sex: female
    258 days
    AnAge
  • Average age at sexual or reproductive maturity (male)
    Sex: male
    456 days
    AnAge

Lifespan/Longevity

Behavior

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)

Communication and Perception

Food Habits

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)

Economic Importance for Humans: Positive

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

  • Positive Impacts
  • food
  • body parts are source of valuable material

Economic Importance for Humans: Negative

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)

Conservation Status

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Contributors

Nghi Tran (author), University of Michigan-Ann Arbor.

Glossary

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

chemical

uses smells or other chemicals to communicate

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

granivore

an animal that mainly eats seeds

herbivore

An animal that eats mainly plants or parts of plants.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

young precocial

young are relatively well-developed when born

References

Birney, E.C. and Day-Baird, D.1985. Why Do Some Mammals Polyovulate to Produce a Litter of Two? American Naturalist, vol 126(1):136-140.

Branch, L.C. Nov. 1993. Intergroup and Intragroup Spacing in the Plains Viscacha, Lagostomus maximus. Journal of Mammalogy, vol 74(4):890-900.

Branch, L.C. 1993. Social Organization and Mating System of the Plains Viscacha. Journal of Zoology, vol 229(3):473-491.

Branch, L.C., Villarreal, D. and Fowler, G.S. 1994.Factors Influencing Population Dynamics of the Plains Viscacha, Lagostomus maximus. Journal of Zoology, vol 232(3):383-395.

Branch, L.C., Villarreal, D. and Fowler, G.S. 1993. Recruitment, Dispersal and Group Fusion in a Declining Population of the Plains Viscacha. Journal of Mammalogy, vol 74(1):9-20.

Jackson, J.E., Branch, L.C., and Villarreal, D. Lagostomus maximus. 1993. Mammalian Species, vol 543: 1-6.

Nowak, R.M. 1991. Walker's Mammals of the World. Fifth Edition. Johns Hopkins University Press, Baltimore.

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