Hypogeomys antimena
Malagasy giant rat

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. (Sommer and Tichy, 1999)

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. (Nowak, 1999)

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. (Nowak, 1999; Sommer, 2000)

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. (Nowak, 1999; Sommer, 2000)

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. (Sommer, 2000)

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. (Nowak, 1999; Sommer, 2001)

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. (Nowak, 1999; Sommer, 2000)

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. (Sommer, 2000)

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.

Malagasy giant rats live in social family groups consisting of a male, female, their current offspring, and their offspring from the previous year. Young females stay close to the burrow site, whereas males travel farther to find a new territory. Males and females mate for life, and generally return to the same burrow year after year. Malagasy giant rats rarely leave their territories or enter another territory. They are primarily nocturnal. (Sommer, 2000)

Each monogamous couple defends a home range of about 3.5 ha. During the dry season, before the offspring are born, home ranges are larger than during the rainy season. Malagasy giant rats with young have a smaller range than those without young. (Sommer, 1997)

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.

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. (Nowak, 1999)

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. (Sommer, 2000)

Malagasy giant rats are an important prey species for both fossas and boas. They also help to aerate the soil through their fossorial behavior. (Sommer, 2000)

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. (Sommer and Tichy, 1999)

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

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. (Sommer and Tichy, 1999)