Like rabbits, Malagasy giant rats live in burrows, which typically consist of a network of tunnels, each around 45 centimetres in diameter and up to five metres long (2). These are occupied by a family group consisting of a monogamous pair, their current offspring and their female offspring from the previous year. Families maintain and defend a territory covering three to four hectares (6). Territory borders are marked with urine, faeces and scent gland deposits. The burrows are not only used for raising offspring, but also for protection against predation and heat during the day and heavy rain during the night (4). Pairs mate for life, but if one mate dies they are normally replaced within a few days or weeks (6). Litters of one or two young are born in the rainy season in late November and early December (5), after a gestation period of 102 to 138 days (4). Young stay within the safety of the burrow for the first four to six weeks before venturing out (4). Male offspring leave their natal territory and are able to breed at one year, if they can establish a territory and attract a mate. Female offspring may remain with their parents for up to two years before they get sexually mature and disperse (4). Males are thought to be monogamous in order to help protect their young from high levels of predation and the contribution of male parental care is assumed to be very high (6). This nocturnal rodent spends the day within its burrows, emerging at dusk to forage either alone or in pairs on the forest floor (4). The rats are primarily herbivorous, feeding on fallen fruit, seeds and leaves, digging for roots and tubers and stripping bark from saplings (4), although in captivity some have also been observed eating invertebrates (2).

The Malagasy giant rat is no ordinary rat and bears little resemblance to its better known cousins, having been isolated on the island of Madagascar for much of its evolutionary history (3). About the size of a rabbit, this rotund rodent is by far the largest on Madagascar and, much like a rabbit, possesses long, pointed, conspicuous ears (4). Also known as the Malagasy giant jumping rat, this unusual species has elongated hindlegs and large hind feet that allow it to leap almost a metre into the air. However, contrary to this common name, these 'jumping rats' rarely jump, unless startled or to avoid predators (5). The short fur is greyish-brown to reddish on the upperside, darkest on the head, while the limbs, feet and underparts are white, and the dark tail is covered with short, stiff hairs (2).

This species is endemic to Madagascar, where it is restricted to the west of the island in a narrow coastal zone. The southern limit is now the Tomitsy River (until recently it ranged south to the the Andranomena River) up to the Tsiribihina River in the north (Sommer 2003). In the last century, the species ranged from the Morondava River to the Tsiribihina in the north, but the species has lost significant portions of its range, and is now found in two isolated range segments (separated by the Mandroatra River). The total range is estimated to be less than 200 km². The species is found from 60-100 m asl.

Subfossil remains indicate that over the past 1400 years, the range of H. antimena extended at least 475 km further south (Goodman and Rakotondravony 1996).

Malagasy giant rats are found within a 20x40 km area on the western coast of the island of Madagascar. Hypogeomys antimena is found north of the city of Morondava and between the rivers Tomitsy and Tsiribihina.

Biogeographic Regions: ethiopian (Native )

Other Geographic Terms: island endemic

Found in a small area of western Madagascar called Menabe, northeast of Morondava (6). A village splits the habitat in two, isolating a northern population from one further south (7).

Both males and females are the same size, weighing 1.2 kg and measuring 30 to 35 cm in length. The tail is an additional 21 to 25 cm. Hypogeomys antimena has large ears, about 50 to 60 mm.

Malagasy giant rats have harsh pelage, with its upper parts gray, grayish-brown, or reddish. The head is the darkest part of the fur. The limbs, hands, feet, and under parts are white. The dark tail is covered with stiff, short hairs. These rats possess a long hind foot with relatively well developed claws.

Range mass: 1000 to 1500 g.

Average mass: 1200 g.

Range length: 300 to 350 mm.

Average length: 300 mm.

Sexual Dimorphism: sexes alike

Habitat and Ecology

Systems

• Terrestrial

Hypogeomys antimena is found in sandy coastal areas and dry deciduous forests on the western coast of Madagascar. It lives in long deep burrows that are about 5 meters in length and have 1 to 6 holes.

Habitat Regions: temperate ; terrestrial

Terrestrial Biomes: forest

Restricted to sandy coastal areas of primary dry deciduous forest, mixed with baobab trees and permanently covered in dry leaf-litter (2).

Hypogeomys antimena is herbivorous. These rats are thought to feed mainly on fallen fruit, though some have been observed eating vegetation and invertebrates in captivity.

Animal Foods: insects

Plant Foods: leaves; seeds, grains, and nuts; fruit

Primary Diet: herbivore (Frugivore )

Malagasy giant rats are an important prey species for both fossas and boas. They also help to aerate the soil through their fossorial behavior.

Ecosystem Impact: soil aeration

There are two main predators that feed on H. antimena. These are a small herpestid found only on Madagascar, Cryptoprocta ferox (fossa), and the snake, Acrantophis dumerili (Dumeril's ground boa). One study found that 64.7% of the Malagasy giant rats killed during the dry season were taken by fossas, with the remaining 35.5% killed by Dumeril's ground boa.

It is thought that monogamy in H. antimena may be an antipredator adaptation, allowing greater protection of the young while they are waiting to reach maturity.

Known Predators:

• fossae (Cryptoprocta ferox)
• Dumeril's ground boas (Acrantophis dumerili)

Hypogeomys antimena preys on:
Insecta

This list may not be complete but is based on published studies.

Hypogeomys antimena is prey of:
Boa dumerili
Cryptoprocta ferox

This list may not be complete but is based on published studies.

There is little available information on communication in H. antimena. However, they are mammals, and so it is likely that they use some visual signals, some vocalizations, and some scent cues in their communication. Tactile communication is probably important between mates and within the family.

Communication Channels: visual ; tactile ; acoustic ; chemical

Perception Channels: visual ; acoustic

There is little information available information on the lifespan of H. antimena. The species likely has a relatively long lifespan because of high parental care and the long time to maturity.

Range lifespan

Status: captivity: 12.6 (high) years.

Maximum longevity: 12.6 years (captivity) Observations: Males are sexually mature at one year of age but do not normally reproduce until they are two years of age. Females generally stay with parents for two years. In the wild, these animals are capable of reproducing up to 7 years of age (Sommer et al. 2002). One captive specimen lived 12.6 years (Richard Weigl 2005). The high parental care and long time to maturity partly explain the longer lifespan than that of similar species.

Hypogeomys antimena is monogamous until one mate dies. The male is sexually mature after one year and the female is sexually mature at two years. It is thought that males of this species are monogamous due to high predation. Males will defend their offspring from predators, putting themselves at higher predation risk than females. Pairs defend an exclusive territory throughout the year. Males rarely ever go into a neighboring territory.

Mating System: monogamous

Females of this species give birth during the rainy season, between December and April. An average litter contains one or two young. The average gestation period is from 102 to 138 days. The young stay in the burrow for the first 4 to 6 weeks of their lives, but regularly leave it after 4 weeks. Males leave the parental burrow and territory after one year and are able to breed immediately. Females are not sexually mature until two years of age, and they will usually stay with the parents through the next breeding season (until April) before they disperse.

Breeding interval: Malagasy giant rats breed once yearly.

Breeding season: Malagasy giant rats breed during the rainy season, December to April.

Range number of offspring: 1 to 2.

Average number of offspring: 1.

Range gestation period: 102 to 138 days.

Range weaning age: 4 to 6 weeks.

Average weaning age: 4 weeks.

Range time to independence: 12 to 24 months.

Average age at sexual or reproductive maturity (female): 2 years.

Average age at sexual or reproductive maturity (male): 1 years.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); fertilization ; viviparous

Average number of offspring: 1.

Average age at sexual or reproductive maturity (male)

Sex: male: 365 days.

Average age at sexual or reproductive maturity (female)

Sex: female: 730 days.

Females have obvious roles in parental care in all mammalian species. The female nurses the young, grooms them, and protects them from harm. Because the young are altricial, it takes some time before they are developed enough to leave the nest. The duration of lactation is approximtely 4 to 6 weeks in this species.

Malagasy giant rats are intereting because of the level of male parental care they exhibit. Adults and juveniles have the same predators, and males increase their own predation risk to protect their young. Juvenile and adult males tend to wander farther away from the burrow than the females, increasing the male predation levels. Adult males will often follow their male offspring in order to protect them from predators.

Because it takes females two years to reach reproductive maturity, they often stay at home with their parents during this time. This is an extended period of interaction between female young and their parents.

Parental Investment: no parental involvement; altricial ; pre-fertilization (Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Male, Female); pre-independence (Protecting: Male, Female); post-independence association with parents

Year Assessed

Assessor/s

Reviewer/s

Justification

History

• 1996
  Endangered
• 1994
  Insufficiently Known
  (Groombridge 1994)

Hypogeomys antimena is among the most endangered mammal species of Madagascar. The habitat of Malagasy giant rats is threatened by slash and burn agriculture and logging. There is little information available on what is being done to help the species.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: endangered

Classified as Endangered (EN) on the IUCN Red List 2007 (1).

Population

Population Trend

Major Threats

Like many of Madagascar's unique species, the Malagasy giant rat is thought to have become highly endangered due to habitat loss and disturbance, and predation by and competition with introduced species (8). For centuries Madagascar's forests have experienced successive waves of degradation at the hands of human colonists, each with different destructive patterns of land use (7). In more recent years, illegal and commercial logging, charcoal production and burning to clear land for agriculture or cattle pasture have all had a devastating impact, often changing open forest into dense, shrubby undergrowth unsuitable as rat habitat or destroying the vegetation completely (3). The rats continue to suffer from human disturbance in the remaining forests, which are used by the villagers to gather firewood, collect honey, dig up edible roots, and hunt tenrecs and lemurs (3) (7). Predation by introduced predators such as dogs may also be playing a significant role in this species' decline (3).

Conservation Actions

This large rodent is in urgent need of conservation and its future remains highly uncertain. The Durrell Wildlife Conservation Trust is currently working closely with the Madagascan government and local community to help protect the species, and has also established a captive breeding programme (5). The Menabe Forest, an Alliance for Zero Extinction site due to the presence of this and a number of other endangered species, was previously heavily impacted by subsistence farming, wood extraction, and livestock ranching. Fortunately, in order to protect its unique but rapidly diminishing biodiversity, the Madagascan government aims to expand the nation's protected area network and, on March 28, 2006, the Minister of the Environment, Water and Forests signed a decree giving 125,000 hectares of Menabe Forest temporary protected status. This is the first step towards making the site an official protected area. However, while community and conservation groups have begun the slow process of agreeing on the official boundaries and goals of the new protected area (9), prospectors have begun using dynamite to search for oil reserves in Menabe, causing concerns about further forest degradation (7). Official, full protected status is urgently needed in this area if the Malagasy giant rat is to be successfully brought back from the brink of extinction.

There are no known adverse affects of Malagasy giant rats on humans.

There is no information of the benefits of Malagasy giant rats to humans. It is the largest endemic rodent of the island of Madagascar and is the only living species within the genus. It is monogamous, which makes this species of scientific interest.

Positive Impacts: research and education