Degu

The common degu is a small rodent endemic to the Chilean matorral of central Chile, related to the chinchilla and guinea pig. Strictly herbivorous, it feeds on grasses, shrub leaves and seeds, and eats its own faecal pellets to extract more nutrition. Degus are highly social and diurnal. They live in burrows, digging together in coordinated chains to build larger and more elaborate tunnel systems than one animal could manage alone. Females nest communally and nurse one another's young. Their vocal repertoire has up to 15 sounds. A striking trait is their ultraviolet vision, which may play a social role, as their belly fur and urine reflect UV strongly.

About the degu

The common degu is a small, social rodent found only in the matorral shrublands of central Chile. It belongs to the caviomorph rodents, the same group as the chinchilla and the guinea pig. Active by day, it lives in shared burrows and has become a familiar pet and research animal far beyond its native range.

Its scientific name is Octodon degus. The genus name refers to the cheek teeth, whose chewing surfaces are shaped like a figure eight. "Degu" comes from the Mapuche word dewü, meaning mouse or rat, and on its own the name can mean either the whole genus Octodon or, more often, just this species. The common degu is smaller than its two relatives in the genus and has a more noticeably tufted tail.

A degu looks a bit like an oversized gerbil. The body measures 25 to 31 cm (9.8 to 12.2 in), and adults weigh about 170 to 400 g (6 to 14 oz), with males around 10% larger than females. As a pet it falls between a golden hamster and a fancy rat in size.

The fur is yellow-brown on the back and head and creamy yellow underneath, with a pale ring around each eye and, in some animals, a paler band around the neck. The coloring is counter-shaded and matches the soil, helping degus stay hidden. The ears are large, dark and sparsely furred, and the long, thin tail ends in a black tuft. On the front feet, the small fifth toe carries a nail instead of a claw, and the hind feet are bristled.

The tail has a built-in escape trick. Its skin and tuft pull off easily, which helps a degu slip free from a predator, though the loss is painful and the tail tip never grows back.

Behavior and diet

Degus are diurnal, most active in the morning and evening, and in high summer they stay underground through the heat of midday. Unlike some of their relatives, they have good vision. Their eyes have cones sensitive to green and to ultraviolet light, and experiments show they can tell UV light apart from the colors people see. Since their belly fur and urine both strongly reflect UV, this ability probably plays a social role.

Life in a colony

Degus are highly social. A typical group has one or two males and two to five related females. They dig communally, lining up in coordinated digging chains, and together they build burrow systems far larger than one animal could manage. Bennett's chinchilla rats often share these burrows, sometimes even the same chamber.

They are also talkative, with up to 15 different calls, and they scent-mark with urine. Dust bathing is a group activity: degus return again and again to favorite wallows and mark them with urine and gland secretions, which may help group members recognize one another and mark territory. Groups occupy roughly 200 square meters (2,150 sq ft).

Foraging happens above ground, and degus sometimes climb into low shrub branches. Larger groups spot predators sooner, so each degu can spend less time on guard. When a predator appears, they give alarm calls and run for shrubs or the burrow. Culpeo foxes, barn owls, short-eared owls and black-chested buzzard eagles all hunt them.

What degus eat

Degus are strictly herbivorous. In the wild they eat grasses, the leaves and bark of shrubs, annual plants and seeds, including thistle seeds. Much of their food is dry for most of the year, and they are adapted to a very high-fiber diet. They pick young, tender leaves and avoid woodier, thornier shrubs, which shapes the plant community around them. They also store food for winter.

Like rabbits, degus eat a large share of their own droppings, usually at night, to extract more nutrition. Fermentation by microbes in an enlarged cecum does much of the digestion. Degus cannot handle dietary sugar well. Their insulin has an unusual structure, and they easily develop diabetes if fed free sugars, probably because their natural diet contains almost none.

Family life

Degus breed seasonally. In the wild, mating starts in the Chilean autumn, and pups arrive in early to mid-spring after a pregnancy of about 90 days, which is long compared with rodents outside the caviomorph group. Litters average six pups but can range from one or two up to twelve.

The pups are born well developed: furred, eyes open, able to see and hear, and exploring within hours. Females in a group often nest together and nurse one another's young. Unusually for rodents, fathers help protect and raise the pups until they leave the family.

Clever rodents

Degus are popular research animals, partly because of their link to diabetes. In experiments they spontaneously learned to use a tiny rake to pull seeds within reach, and they have stacked objects in order of decreasing size. These were the first records of such behavior outside apes and birds.

Range and habitat

The common degu is endemic to west-central Chile, on the lower western slopes of the Andes. It lives in the matorral, a semi-arid, Mediterranean-type shrubland found between about 28° and 35° south. Farther north it is too dry for this plant community, and farther south too wet.

Degus are limited to elevations below about 1,200 m (3,900 ft), both by where the matorral grows and because they tolerate thin air poorly. They do well on land grazed by cattle and are crop pests in some places. Population density has been estimated at about 75 degus per hectare (30 per acre).

Conservation status

The common degu is listed as Least Concern on the IUCN Red List, assessed in 2016. Although its natural range is small compared with many rodents, it breeds prolifically and is considered the most common mammal within that range. It has no special U.S. federal or CITES status.

Because degus are so plentiful, they are an important food source for local predators. Outside Chile, some jurisdictions treat them as a potential invasive species. In the United States, keeping degus as pets is illegal in California, Utah, Georgia, Connecticut and Alaska.