Cavia magna

greater guinea pig

Features
By Chelsea Rasnic

Geographic Range

Greater guinea pigs ( Cavia magna ) are native to the neotropical region, in South America, and are mainly found in Brazil and Uruguay. They were originally found in Rio Grande de Sul, Brazil and are native to the northwest Atlantic coast. Their native range extends as far south as the Department of Rocha, Uruguay and as far north as Criciuma, Brazil. They are located between longitudes 54° to 49° W and between the latitudes 34° to 29° S.

Habitat

Greater guinea pigs are non-burrowing cavies (family Caviidae ). They stay near water sources such as rivers, lakes, or oceans, and are most commonly found in wetlands. Greater guinea pigs do not migrate, but they move between habitats depending on seasonal weather changes. For example, in the wet season they move to drier areas within their home range that have not been inundated with water.

In wetland habitats, greater guinea pigs seek shelter in giant sea holly ( Eryngium pandanifolium ), a species of tall, spiny shrub. The height and spines of giant sea holly provide cover and protection for greater guinea pigs. Greater guinea pigs are completely terrestrial and select habitats based on the presence of predators, food, and water levels. Because greater guinea pigs live near sea level, flooding is common and they are occasionally forced to move. Depending on water levels, greater guinea pigs may be found outside of grasslands, where they escape from potential predators. They use small shrubs and grasses located on the borders of their home range for protection and shelter.

Physical Description

Greater guinea pigs have coarse fur, no tails, and small, hairless ears. They have long fur, particularly on their necks, where their pelage forms a crest. Their fur ranges in coloration from dark gray to dark brown. Greater guinea pigs are 200 to 400 mm in length and 500 to 1,500 g. The average weight of adult males and females is around 750 g. Greater guinea pigs are stocky, with short legs relative to their length. They have four digits on their front feet and three digits on their hind feet. Greater guinea pigs lack canine teeth and have a toothless region, called a diastema, between their incisors and molars. Their incisors grow continuously and must be maintained by gnawing on tough materials, such as wood. The dental formula for greater guinea pigs is not known. However, the dental formula for domestic guinea pigs ( Cavia porcellus ) is 1/1, 0/0, 0/0, 4/4, and it is assumed that the dental formula for greater guinea pigs is the same or similar.

Greater guinea pigs are morphologically and genetically similar to Brazilian guinea pigs ( Cavia aperea ) and Santa Catarina's guinea pigs ( Cavia intermedia ). Greater guinea pigs are the largest of these three species, with darker hair on their heads and backs, making them appear more black than brown. Greater guinea pigs also have wider upper molars than other guinea pig species. They also have longer digits than Brazilian and Santa Catarina's guinea pigs. Greater guinea pigs and Santa Catarina's guinea pigs are the only two guinea pig species with interdigital membranes. These are folds of skin between their digits, which are an adaptation to the wetland habitat and semiaquatic lifestyle of the two guinea pig species.

Reproduction

Greater guinea pigs are solitary, though individuals in the same area typically have overlapping home ranges. They are promiscuous, exhibiting scramble competition polygyny, also known as overlap promiscuity, where males mate with females that overlap their home ranges. Males continuously search for mates throughout the year, and there are typically 3 males for every oestrous female.

Greater guinea pigs are viviparous, meaning they birth live young. They generally have a seasonal period of reproduction, but they may also mate outside of that period. September to December is the highest period of reproductive activity, with over half of the reproductive events occurring in October. Reproductive activities tend to be minimal to nonexistent between May and September. On average, greater guinea pigs have 3 (range: 2 to 4) reproductive bouts per year and a gestation period of 53 to 77 days. Reproduction among females in a population is synchronous in the beginning of the breeding period, but becomes less synchronous throughout the year.

Females can reach reproductive maturity, on average, at 29.5 days old, when they are only 50% of their adult body mass. Only females born in the first reproductive cohort of the year reproduce this early. Females born later in the reproductive season delay their reproductive maturity and begin breeding at 3 to 10 months old, when they weigh 319 to 412 g. Litters consist of 1 to 4 young weighing 54 to 76 g, approximately 18% of the weight of the mother. Greater guinea pigs have an average of 5.1 pups a year. Individual litters tend to be sex biased, with more male births during peak reproductive season. However, later in the reproductive season there is a shift to more female births in litters. There is typically a high rate of male mortality or emigration shortly after they are born. Most species in the family Caviidae go through a post-partum estrous cycle shortly after birthing.

Female greater guinea pigs increase in weight up to 42% while pregnant and decrease their activity to conserve energy. Newborn greater guinea pigs are precocial. They are born fully furred with their eyes wide open. They are mobile shortly after birth and can ingest solid foods within the first week. Male and female pups initially grow at the same rate, but females stop growing sooner than males. Pups stay near their mothers for 3 to 5 weeks, when the mothers are still lactating. Females alienate any pups that are not their own and will be aggressive towards them. Males show paternal actions towards their pups by grooming and social play without aggression.

Lifespan/Longevity

There is limited information regarding the average lifespan of greater guinea pigs specifically. However, other members of the genus Cavia , such as Brazilian guinea pigs ( Cavia aperea ) and Peruvian guinea pig ( Cavia tschudii ) live approximately 6 years. It is expected that greater guinea pigs have a similar lifespan in the wild. No known captive populations exist.

Behavior

Greater guinea pigs differ from other cavies (family Caviidae ) because the water levels in their wetland habitats are constantly in flux. They are terricolous animals that do not burrow. They are typically solitary, with the exception of mating season. Greater guinea pigs are nocturnal most of the year, especially during the summer, but they are more crepuscular during the winter and are occasionally active in late afternoons.

Not much is known about communication behaviors in greater guinea pigs, but other members of the genus Cavia exhibit agonistic and sexual behaviors. It is expected that greater guinea pigs behave similarly. They show agonistic behaviors such as thrusting their heads, chasing, and biting each other. Guinea pigs of the same sex display agonistic behaviors towards each other, but interactions with individuals of the opposite sex are mostly related to reproduction. The majority of intraspecific interactions occur between males and females whose home ranges overlap.

Home Range

Immigration and emigration is common for greater guinea pigs. They do not have stable home ranges due to consistent water level fluctuations in their territory. Nevertheless, even when water levels are low, home range overlap of males and females occurs. Males have a larger average home ranges than females, and thus their home ranges overlap with more individuals. Male home ranges extend from 5,620 to 18,040 m² with an average of 11,830 m², and female home ranges range from 3,700 to 11,640 m² with an average of 7,670 m². Males are not territorial of their home range or of the females inhabiting their home range.

Communication and Perception

Greater guinea pigs use chemoreception to communicate. While courting, males urinate on females. Additionally, females reject males by spraying urine on them. Males also smear excrement and anal gland secretions on the ground to mark their territories. Research on greater guinea pigs has shown that females become sexually mature sooner when raised together with males. Greater guinea pigs also communicate acoustically. They emit high-pitched squeaks when excited, chirping noises when stressed, and they chatter with their teeth to ward off threats.

Food Habits

Greater guinea pigs are obligate herbivores, and they specifically eat foliage, such as energy-poor grasses and leaves. Their energy-poor diets are due to their habitats being occasionally muddy or underwater and consisting only of short-grasses and shrubs. There is limited information regarding the food habits of cavies (family Caviidae ) other than in a domesticated environment.

Predation

Greater guinea pigs use cryptic behavior to avoid predators. They forage less than 4 m from tall, dense vegetation at all times, so they can return to cover if they spot predators. When a predator is nearby, they remain completely still in dense vegetation unless the predator comes within a few meters of them, at which point they flee. Regardless, there is a high rate of mortality in greater guinea pigs. A study in 2003 showed that predators killed 92% of the greater guinea pigs being radio tracked between October and January. Lesser grisons ( Galictis cuja ) were the major predators in the study, accounting for over 75% of the individuals that were killed. Greater guinea pigs are at the highest risk of predation in dry summer months.

Other mammalian predators of greater guinea pigs include crab-eating foxes ( Cerdocyon thous ) and little water opossums ( Lutreolina crassicaudata ). Greater guinea pigs also serve as prey for birds of prey, including cinereous harriers ( Circus cinereus ), long-winged harriers ( Circus buffoni ), roadside hawks ( Buteo magnirostris ), chimango caracaras ( Milvago chimango ), southern crested caracaras ( Polyborus plancus ), and great horned owls ( Bubo virginianus ). Also, snakes such as Patagonia green racers ( Philodryas patagoniensis ) are predators of greater guinea pigs.

Ecosystem Roles

A 2004 study cited unpublished data from one of the authors which suggests that greater guinea pigs serve as hosts for parasites, but the parasite species were not listed. However, their close relatives, Brazilian guinea pigs ( Cavia aperea ) serve as hosts to nematodes, trematodes, fleas, lice, and mites. It is likely that greater guinea pigs serve as hosts for similar parasites.

Economic Importance for Humans: Positive

Greater guinea pigs do not interact with humans because of their isolated habitats. Other members of the genus Cavia have been used as a source of meat for humans, and greater guinea pigs would most likely serve as a source of protein if in contact with humans.

Economic Importance for Humans: Negative

There are no known adverse effects of greater guinea pigs on humans.

Conservation Status

Greater guinea pigs are considered a species of “Least concern” on the IUCN Red List, but their populations are in decline. Mortality in greater guinea pigs is mostly caused by predation or water levels rising quickly within their habitat. Greater guinea pigs are also threatened by the development of their natural wetland habitats into pastureland for cattle ranching. There are no conservation measures in place for greater guinea pigs specifically, but their geographic range includes four protected areas in Brazil and Laguna de Castillos, a protected area in Uruguay. Greater guinea pigs are not listed in the CITES appendices or in any other federal or international endangered species lists.

Encyclopedia of Life

Contributors

Chelsea Rasnic (author), Radford University, Karen Powers (editor), Radford University, April Tingle (editor), Radford University, Emily Clark (editor), Radford University, Cari Mcgregor (editor), Radford University, Jacob Vaught (editor), Radford University, Galen Burrell (editor), Special Projects.

Neotropical

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

World Map

native range

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

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

terrestrial

Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

scrub forest

scrub forests develop in areas that experience dry seasons.

marsh

marshes are wetland areas often dominated by grasses and reeds.

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

seasonal breeding

breeding is confined to a particular season

sexual

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

fertilization

union of egg and spermatozoan

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

young precocial

young are relatively well-developed when born

male parental care

parental care is carried out by males

female parental care

parental care is carried out by females

nocturnal

active during the night

crepuscular

active at dawn and dusk

motile

having the capacity to move from one place to another.

solitary

lives alone

visual

uses sight to communicate

tactile

uses touch to communicate

acoustic

uses sound to communicate

chemical

uses smells or other chemicals to communicate

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

visual

uses sight to communicate

tactile

uses touch to communicate

acoustic

uses sound to communicate

chemical

uses smells or other chemicals to communicate

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

herbivore

An animal that eats mainly plants or parts of plants.

folivore

an animal that mainly eats leaves.

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.

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.

References

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To cite this page: Rasnic, C. 2023. "Cavia magna" (On-line), Animal Diversity Web. Accessed {%B %d, %Y} at https://animaldiversity.org/accounts/Cavia_magna/

Last updated: 2023-24-18 / Generated: 2025-10-03 01:00

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