Degu
Encyclopedia
The degu is a small caviomorph
rodent
that is endemic to central Chile
.
It is sometimes referred to as the brush-tailed rat, and is also called the common degu, to distinguish it from the other members of the genus Octodon
. Other members are also called degus, but they are distinguished by additional names. The name "degu" on its own, however, indicates either the genus Octodon or, more usually, O. degus. Degus are in the parvorder Caviomorpha
of the infraorder Hystricognathi
, along with the chinchilla
and guinea pig
. The word degu comes from the Mapudungun
dewü (mouse, rat).
name "Octodon".
to scent mark, and experiments have shown that they react to one another's marks, although in males the hormone testosterone
may suppress their sense of smell somewhat.
Degus are seasonal breeders; the breeding season for wild degus begins in the Chilean autumn when there is roughly 12 hours light:12 hours darkness, with pups born in early to mid spring. Female degus are pregnant for approximately ninety days, having a comparatively long gestation period compared to other non-caviomorph rodents. Female pregnant weight varies over the course of gestation and according to litter size; litters contain an average of six pups, but size can range from one or two up to twelve young. Degu pups are born relatively precocial
, fully furred and with eyes open, and their auditory
and visual system
s are functional at birth. Unlike most other rodents, male degus also take part in protecting and raising their pups until they are old enough to leave the family.
Unlike some other octodontids
, degus are diurnal (active during the day), and they have good vision. Their retina
s include rod cell
s and two types of cone cell
s, corresponding to peak sensitivity in the green and ultraviolet
regions of the spectrum
. Behavioral experiments have shown that degus are able to discriminate ultraviolet light from the wavelengths visible to humans; it is likely that this ultraviolet sensitivity has a social function, since both their ventral (stomach) fur and their urine
are highly UV reflective.
s, they perform coprophagy
(faecal
reingestion) so as to extract more nutrition from their diet. This also serves to maintain healthy gut function during times when food is scarce. Although they are active by day, in high summer they do not leave their burrows in the middle of the day and instead emerge to forage in the mornings and evenings.
Perhaps the most remarkable feature of degu physiology is their intolerance of dietary sugar. Degus have been found to have a divergent insulin
structure (one of the hormones that regulates blood glucose level) and so are highly susceptible to developing diabetes mellitus
when fed regularly on a diet containing free sugars. This is thought to be due to evolutionary pressure arising from the lack of availability of free sugars in the degu's natural environment. Because of this, the ingredients of non-degu specific hard feed formulations given to captive degus should be checked for free-sugar substances, such as molasses
, honey
and glucose syrup
.
Neuroscientists
at the Riken Institute
in Tokyo
, Japan
, used degus for research into tool use in animals with good eye-and-paw coordination, in which they spontaneously learned to use a tiny rake to retrieve out-of-reach seeds. Degus have also been found to spontaneously stack objects in order of decreasing size. In both cases it is the first time these behaviours have been recorded in animals other than apes and birds.
Another interesting area of degu research is circadian rhythm
function, i.e. the ability of the brain to tell what time of day it is. Degus have the ability to show both diurnal and nocturnal rhythms if the environment permits, allowing a unique opportunity for study. Degus can take cues that do not relate to day length, such as temperature, melatonin
levels and even scents from other degus to adjust their rhythms.
Degus are also invaluable in development and aging studies. Research has shown that separation anxiety
caused by separating pups from their mother from an early age for periods of half an hour or more can cause developmental and behavioural changes in later life, similar to ADHD in humans. In elderly degus, neural markers have been discovered which are remarkably similar to those in humans with Alzheimer's disease
, which is the first time this has been seen in a non-human mammal.
s and mice
) and their lifespan: they are reported to live up to 13 years under ideal circumstances (though a poor gene pool/genetic background often reduces a pet degu's lifespan significantly). The average lifespan of a degu in captivity is typically around 6–8 years of age. One disadvantage of the degu as a pet is their predisposition to chewing, due to their continually growing incisor and molar teeth. For this reason degus cannot be housed in plastic-bottomed cages typically found in pet stores. A metal cage with multiple levels made for rats and secured double latches works best. It is important to line the levels with grass mats or a soft fabric so that the degus do not get bumble feet
. Untamed degus, as with most small animals, can be prone to biting, but their intelligence makes them easy to tame. Regular non-predatory handling and food offerings help with this transition. It is important never to try to catch a degu by the tail because it will fall off easily and is painful to the creature. If this occurs it will not grow back. Degus often 'groom' their human owners, by a gentle nibbling action, and readily bond with any person spending time with them. Degus need regular sand baths to keep their coats healthy and free from grease. Chinchilla dust is ideal for this. They should have access to this regularly, preferably every day but at least two or three times a week.
Caviomorpha
Caviomorpha is the rodent infraorder or parvorder that unites all South American hystricognaths. It is supported by both fossil and molecular evidence.-Origin:...
rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
that is endemic to central Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
.
It is sometimes referred to as the brush-tailed rat, and is also called the common degu, to distinguish it from the other members of the genus Octodon
Octodon
Octodon is a genus of octodontid rodents, of which the best-known member is the degu O. degus. The full list of species is:* O. bridgesi, Bridge's Degu, found in Argentina and Chile...
. Other members are also called degus, but they are distinguished by additional names. The name "degu" on its own, however, indicates either the genus Octodon or, more usually, O. degus. Degus are in the parvorder Caviomorpha
Caviomorpha
Caviomorpha is the rodent infraorder or parvorder that unites all South American hystricognaths. It is supported by both fossil and molecular evidence.-Origin:...
of the infraorder Hystricognathi
Hystricognathi
Hystricognathi is an infraorder of rodents. Hystricognaths are distinguished from other rodents by the bone structure of their skulls. The masseter medialis passes partially through the infraorbital foramen and connects to the bone on the opposite side...
, along with the chinchilla
Chinchilla
Chinchillas are crepuscular rodents, slightly larger and more robust than ground squirrels, and are native to the Andes mountains in South America. Along with their relatives, viscachas, they make up the family Chinchillidae....
and guinea pig
Guinea pig
The guinea pig , also called the cavy, is a species of rodent belonging to the family Caviidae and the genus Cavia. Despite their common name, these animals are not in the pig family, nor are they from Guinea...
. The word degu comes from the Mapudungun
Mapudungun
The Mapuche language, Mapudungun is a language isolate spoken in south-central Chile and west central Argentina by the Mapuche people. It is also spelled Mapuzugun and sometimes called Mapudungu or Araucanian...
dewü (mouse, rat).
Description
The degu is a small rodent with a body length of 25 to 31 cm (9.8 to 12.2 in) and a weight of 170 to 300 g (6 to 10.6 oz). It has yellow-brown fur above and creamy-yellow below, with yellow around the eyes and a paler band around the neck. It has a long, thin tail with a tufted black tip, dark sparsely-furred ears, and pale grey toes. Its fifth toe is small with a nail, rather than a claw, on the forefeet. Its hindfeet are bristled. Its cheek teeth are shaped like figures-of-eight, hence the degu's genusGenus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
name "Octodon".
Social behavior
Degus are highly social. They live in burrows, and, by digging communally, they are able to construct larger and more elaborate burrows than they could on their own. Degus digging together coordinate their activities, forming digging chains. Females living in the same group have been shown to spontaneously nest communally; they nurse one another's young. They spend a large amount of time on the surface, where they forage for food. When foraging, their ability to detect predators is increased in larger groups, and each animal needs to spend less time in vigilance. Degus exhibit a wide array of communication techniques. They have an elaborate vocal repertoire comprising up to 15 unique sounds, and the young need to be able to hear their mother's calls if the emotional systems in their brains are to develop properly. They use their urineUrine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
to scent mark, and experiments have shown that they react to one another's marks, although in males the hormone testosterone
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...
may suppress their sense of smell somewhat.
Degus are seasonal breeders; the breeding season for wild degus begins in the Chilean autumn when there is roughly 12 hours light:12 hours darkness, with pups born in early to mid spring. Female degus are pregnant for approximately ninety days, having a comparatively long gestation period compared to other non-caviomorph rodents. Female pregnant weight varies over the course of gestation and according to litter size; litters contain an average of six pups, but size can range from one or two up to twelve young. Degu pups are born relatively precocial
Precocial
In biology, the term precocial refers to species in which the young are relatively mature and mobile from the moment of birth or hatching. The opposite developmental strategy is called "altricial," where the young are born or hatched helpless. Extremely precocial species may be called...
, fully furred and with eyes open, and their auditory
Auditory system
The auditory system is the sensory system for the sense of hearing.- Outer ear :The folds of cartilage surrounding the ear canal are called the pinna...
and visual system
Visual system
The visual system is the part of the central nervous system which enables organisms to process visual detail, as well as enabling several non-image forming photoresponse functions. It interprets information from visible light to build a representation of the surrounding world...
s are functional at birth. Unlike most other rodents, male degus also take part in protecting and raising their pups until they are old enough to leave the family.
Unlike some other octodontids
Octodontidae
The Octodontidae are a family of rodents, restricted to south-western South America. Thirteen species of octodontid are recognised, arranged in nine genera. The best known species is the Degu, Octodon degus....
, degus are diurnal (active during the day), and they have good vision. Their retina
Retina
The vertebrate retina is a light-sensitive tissue lining the inner surface of the eye. The optics of the eye create an image of the visual world on the retina, which serves much the same function as the film in a camera. Light striking the retina initiates a cascade of chemical and electrical...
s include rod cell
Rod cell
Rod cells, or rods, are photoreceptor cells in the retina of the eye that can function in less intense light than can the other type of visual photoreceptor, cone cells. Named for their cylindrical shape, rods are concentrated at the outer edges of the retina and are used in peripheral vision. On...
s and two types of cone cell
Cone cell
Cone cells, or cones, are photoreceptor cells in the retina of the eye that are responsible for color vision; they function best in relatively bright light, as opposed to rod cells that work better in dim light. If the retina is exposed to an intense visual stimulus, a negative afterimage will be...
s, corresponding to peak sensitivity in the green and ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
regions of the spectrum
Electromagnetic spectrum
The electromagnetic spectrum is the range of all possible frequencies of electromagnetic radiation. The "electromagnetic spectrum" of an object is the characteristic distribution of electromagnetic radiation emitted or absorbed by that particular object....
. Behavioral experiments have shown that degus are able to discriminate ultraviolet light from the wavelengths visible to humans; it is likely that this ultraviolet sensitivity has a social function, since both their ventral (stomach) fur and their urine
Urine
Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...
are highly UV reflective.
Diet
Degus are strictly herbivorous, in the wild feeding on grasses and browsing the leaves of shrubs, though they will also take seeds. Throughout much of the year forage is dried and so degus are specially adapted to a very high fibre intake, and this varies between food types and environmental conditions. Like some other herbivores such as rabbitRabbit
Rabbits are small mammals in the family Leporidae of the order Lagomorpha, found in several parts of the world...
s, they perform coprophagy
Coprophagia
Coprophagia or coprophagy is the consumption of feces, from the Greek κόπρος copros and φαγεῖν phagein . Many animal species practice coprophagia as a matter of course; other species do not normally consume feces but may do so under unusual conditions...
(faecal
Feces
Feces, faeces, or fæces is a waste product from an animal's digestive tract expelled through the anus or cloaca during defecation.-Etymology:...
reingestion) so as to extract more nutrition from their diet. This also serves to maintain healthy gut function during times when food is scarce. Although they are active by day, in high summer they do not leave their burrows in the middle of the day and instead emerge to forage in the mornings and evenings.
Perhaps the most remarkable feature of degu physiology is their intolerance of dietary sugar. Degus have been found to have a divergent insulin
Insulin
Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....
structure (one of the hormones that regulates blood glucose level) and so are highly susceptible to developing diabetes mellitus
Diabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
when fed regularly on a diet containing free sugars. This is thought to be due to evolutionary pressure arising from the lack of availability of free sugars in the degu's natural environment. Because of this, the ingredients of non-degu specific hard feed formulations given to captive degus should be checked for free-sugar substances, such as molasses
Molasses
Molasses is a viscous by-product of the processing of sugar cane, grapes or sugar beets into sugar. The word molasses comes from the Portuguese word melaço, which ultimately comes from mel, the Latin word for "honey". The quality of molasses depends on the maturity of the sugar cane or sugar beet,...
, honey
Honey
Honey is a sweet food made by bees using nectar from flowers. The variety produced by honey bees is the one most commonly referred to and is the type of honey collected by beekeepers and consumed by humans...
and glucose syrup
Glucose syrup
Glucose syrup is a food syrup, made from the hydrolysis of starch. Maize is commonly used as the source of the starch in the USA, in which case the syrup is called "corn syrup", but glucose syrup is also made from other starch crops, including potatoes, wheat, barley, rice and cassavap.21...
.
Research subjects
Degus entered the research spotlight due to their unique relationship with sugar and diabetes, but are also studied for a wide variety of other reasons.Neuroscientists
Neuroscience
Neuroscience is the scientific study of the nervous system. Traditionally, neuroscience has been seen as a branch of biology. However, it is currently an interdisciplinary science that collaborates with other fields such as chemistry, computer science, engineering, linguistics, mathematics,...
at the Riken Institute
RIKEN
is a large natural sciences research institute in Japan. Founded in 1917, it now has approximately 3000 scientists on seven campuses across Japan, the main one in Wako, just outside Tokyo...
in Tokyo
Tokyo
, ; officially , is one of the 47 prefectures of Japan. Tokyo is the capital of Japan, the center of the Greater Tokyo Area, and the largest metropolitan area of Japan. It is the seat of the Japanese government and the Imperial Palace, and the home of the Japanese Imperial Family...
, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...
, used degus for research into tool use in animals with good eye-and-paw coordination, in which they spontaneously learned to use a tiny rake to retrieve out-of-reach seeds. Degus have also been found to spontaneously stack objects in order of decreasing size. In both cases it is the first time these behaviours have been recorded in animals other than apes and birds.
Another interesting area of degu research is circadian rhythm
Circadian rhythm
A circadian rhythm, popularly referred to as body clock, is an endogenously driven , roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed in plants, animals, fungi and cyanobacteria...
function, i.e. the ability of the brain to tell what time of day it is. Degus have the ability to show both diurnal and nocturnal rhythms if the environment permits, allowing a unique opportunity for study. Degus can take cues that do not relate to day length, such as temperature, melatonin
Melatonin
Melatonin , also known chemically as N-acetyl-5-methoxytryptamine, is a naturally occurring compound found in animals, plants, and microbes...
levels and even scents from other degus to adjust their rhythms.
Degus are also invaluable in development and aging studies. Research has shown that separation anxiety
Separation anxiety
Separation anxiety may refer to:*Separation anxiety disorder or Separation anxiety test*Spider-Man & Venom: Separation Anxiety, a 1995 SNES video game*Separation Anxieties, a 2000 album by 12 Rods...
caused by separating pups from their mother from an early age for periods of half an hour or more can cause developmental and behavioural changes in later life, similar to ADHD in humans. In elderly degus, neural markers have been discovered which are remarkably similar to those in humans with Alzheimer's disease
Alzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...
, which is the first time this has been seen in a non-human mammal.
Pets
After initial interest into degus as research subjects, degus have become popular as pets, though until very recently they were seldom found in pet shops. Their advantages over traditional small pets are their diurnal habits, bubbly personalities, the haired tail (as compared to ratRat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...
s and mice
Mouse
A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...
) and their lifespan: they are reported to live up to 13 years under ideal circumstances (though a poor gene pool/genetic background often reduces a pet degu's lifespan significantly). The average lifespan of a degu in captivity is typically around 6–8 years of age. One disadvantage of the degu as a pet is their predisposition to chewing, due to their continually growing incisor and molar teeth. For this reason degus cannot be housed in plastic-bottomed cages typically found in pet stores. A metal cage with multiple levels made for rats and secured double latches works best. It is important to line the levels with grass mats or a soft fabric so that the degus do not get bumble feet
Bumblefoot (infection)
Bumblefoot is a bacterial infection and inflammatory reaction on the feet of birds and rodents. This infection is much more likely to occur in captive animals than in those in the wild.- Bumblefoot on birds of prey :...
. Untamed degus, as with most small animals, can be prone to biting, but their intelligence makes them easy to tame. Regular non-predatory handling and food offerings help with this transition. It is important never to try to catch a degu by the tail because it will fall off easily and is painful to the creature. If this occurs it will not grow back. Degus often 'groom' their human owners, by a gentle nibbling action, and readily bond with any person spending time with them. Degus need regular sand baths to keep their coats healthy and free from grease. Chinchilla dust is ideal for this. They should have access to this regularly, preferably every day but at least two or three times a week.