Octodonts: Octodontidae

views updated

OCTODONTS: Octodontidae

PHYSICAL CHARACTERISTICS

Octodonts are similar in appearance and size to gerbils and rats. They have stocky bodies, large heads, pointed noses, and medium-sized rounded ears. Octodonts have rear legs that are slightly shorter than their front legs. They have four clawed toes on their front paws and five on their back paws.

Octodonts have a head and body length of 5 to 8.7 inches (125 to 221 millimeters) and a tail length of 1.5 to seven inches (40 to 180 millimeters). Their weight ranges from 2.8 to 10.6 ounces (80 to 300 grams). They have long, dense, silky fur that is yellow, brown, or gray on their upper bodies and white or cream on their underside. One exception is the coruro, which is almost entirely black.

GEOGRAPHIC RANGE

Octodonts are found in southwest Peru, Chile, Argentina, and southwest Bolivia.

HABITAT

The octodont habitat ranges from coastal scrub brush to barren rocky outcroppings in mountains. They are found in desert, deciduous forest, grassland, and foothills.

DIET

Octodonts are herbivores, meaning they eat only plants. All but one species eat mainly at night. The degu feeds during the early morning and early evening. Most species eat a diet of grass, leaves, herbs, bark, and seeds. The coruro feeds mostly on underground portions of plants.

BEHAVIOR AND REPRODUCTION

All but one species of octodont are nocturnal, meaning they are most active at night. Degus are diurnal, meaning they are most active during daylight hours.

Octodonts are extremely talented and organized diggers. They build burrows consisting of many branched tunnels and multiple entrances. When digging a burrow, the adults form a chain that speeds up the activity. Most octodonts, such as degus, coruros, and rock rats exhibit a complex system of social behavior, living in colonies of five to ten adults and their young. They groom each other, lay bunched together when sleeping, and the females nurse each other's babies. Other species of octodonts are solitary.

The mating system for octodonts is not well understood although in several species it appears to involve courtship rituals. Most species, including the degu and coruro, usually breed twice a year. Females reach puberty, the age of sexual maturity at which they can bear offspring, at six months. The gestation period, the amount of time the young are carried in their mother's womb, is seventy-seven to 105 days. Litters usually consist of four to nine babies.

OCTODONTS AND PEOPLE

Most octodonts have little interaction with humans. Degus are used for laboratory research. They are also sold as pets in the United States. In the wild, degus and coruros are often killed by farmers who consider them agricultural pests, blaming them for destroying grain fields, orchards, and vineyards.

TALE OF THE DEGU TAIL

Never try to catch or pick up a degu by its tail. As a defense against predators in the wild, the end of the tail will come off when it is pulled, allowing the degu to make an escape. However, it results in a bloody injury and can become infected. Usually, part or all of the remaining tail will either dry up and fall off or the degu will chew it off. The lost part never grows back.

CONSERVATION STATUS

The Mocha Island degu is listed by the World Conservation Union (IUCN) as Vulnerable, facing a high risk of extinction, due to their small distribution area. The plains viscacha rat is listed as Vulnerable due to a loss of at least 20 percent of its population within ten years. Other species are not listed by IUCN.

DEGU (Octodon degus): SPECIES ACCOUNT

Physical characteristics: Degus, also called trumpet-tailed rats, are similar in body size and appearance to gerbils, except for the fact that their faces share more of a resemblance with squirrels. They have chubby, round bodies, large heads and short necks. The head and body length of degus are from 9.8 to 12.2 inches (25 to 31 centimeters, with a tail length of 2.9 to 5.1 inches (7.5 to 13.0 centimeters. They weigh 6 to 10.5 ounces (170 to 300 grams).

They have long whiskers and relatively long tails that have very little hair, except for a tuft of fur at the tip. The degus' rear legs are slightly shorter than their front legs. They have four clawed toes on their front paws and five on their back paws. Degus have yellow or brown fur mixed with some black on their upper bodies, and white fur on their underside. Their teeth are bright orange.

Geographic range: In Chile, from the coastal areas of the west slopes of the Andes Mountains to about 9,000 feet (2,700 meters).

Habitat: Degus live in the brush, shrubs, and grassy plains of grasslands and deciduous forests.

Diet: Degus are herbivores, meaning they eat only plants. They eat mainly during the early morning and early evening. Their diet consists mainly of grass, leaves, herbs, bark, and seeds.

Behavior and reproduction: Degus are extremely social and live in groups of five to ten adults and their young. They groom each other, lay bunched together when sleeping, and the females nurse each other's babies. A degu group builds burrows consisting of many branched tunnels and multiple entrances. When digging a burrow, the adults form a chain that speeds up the activity.

Degus are diurnal. In the wild, they live about one to three years. In captivity, their average lifespan is five to nine years, with some reportedly living up to thirteen years.

Degus usually breed twice a year. Females are sexually mature, able to bear offspring, at six months. Litters usually consist of four to nine babies.

Degus and people: Degus are used for laboratory research. They are also sold as pets in the United States. In the wild, degus are often killed by farmers who consider them to be agricultural pests, blaming them for destroying grain fields, orchards, and vineyards.

Conservation status: Degus are not listed as threatened by the IUCN. ∎

FOR MORE INFORMATION

Books:

Boruchowitz, David. The Guide to Owning a Degu. Champaign, IL: TFH Publications, 2002.

Griffiths-Irwin, Diane, and Julie Davis. How to Care for Your Degu. Champaign, IL: TFH Publications, 2001.

Macdonald, David. The New Encyclopedia of Mammals. Oxford, U.K.: Oxford University Press, 2001.

Nowak, Ronald M. Walker's Mammals of the World, 6th ed. Baltimore: Johns Hopkins University Press, 1999.

Vanderlip, Sharon (DVM), and Michele Earle-Bridges. Degus. Hauppauge, NY: Barrons Educational Series, 2001.

Periodicals:

Bacigalupe, Leonardo D., et al. "Activity and Space Use by Degus: A Trade-Off Between Thermal Conditions and Food Availability?" Journal of Mammalogy (February 2003): 331–318.

Begall, Sabine, et al. "Activity Patterns in a Subterranean Social Rodent, Spalacopus cyanus (Octodontidae)." Journal of Mammalogy (February 2002): 153–158.

Begall, Sabine, and Milton H. Gallardo. "Spalacopus cyanus (Rodentia: Octodontidae): An Extremist in Tunnel Constructing and Food Storing Among Subterranean Mammals." Journal of Zoology (May 2000): 53–60.

Gallardo, M. H., and F. Mondaca. "The Systematics of Aconaemys (Rodentia, Octodontidae) and the Distribution of A. sagei in Chile." Mammalian Biology (April 2002): 105–112.

Kenagy, G. J., et al. "Microstructure of Summer Activity Bouts of Degus in a Thermally Heterogeneous Habitat." Journal of Mammalogy (April 2004): 260–267.

Torres-Mura, Juan C., and Luis C. Contreras. "Spalacopus cyanus." Mammalian Species(December 4, 1998): 1–5.

Woods, Charles A., and David K. Boraker. "Octodon degus." Mammalian Species (November 21, 1975): 1–5.