The Degu, Octodon degus, is a small caviomorph that is native to Chile. It is sometimes called Brush-tailed Rat (although not related to the rat family) and is also called the Common Degu, to distinguish it from other members of the genus Octodon. Degus are closely related to chinchillas and guinea pigs. Like Chinchillas, Degus can breed any time of the year. At 90 days, they too have a very long gestation period compared to other rodents. Due to this long pregnancy, degu pups are born fully furred and with eyes open. Litters are usually 4 to 7 in number. Degus are born with their auditory and visual systems fully functional.
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 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. Degu exhibit a wide array of communication techniques. They have an elaborate vocal repertoire, and the young need to be able to hear their mother’s calls if the emotional systems in their brains are to develop properly.
Degus are herbivores, feeding on grasses and browsing the leaves of shrubs, though they will also take seeds. Their feeding rate is constrained by how fast they can digest this relatively low quality food, and this varies between food types and environmental conditions, and like some other herbivores such as rabbits, they chew their own feces so as to extract more nutrition from them. 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 in hot conditions they forage as quickly as possible instead of maximizing the quality of their food. They tend to forage in shaded areas, though this tendency is reduced in the absence of predators. In open areas they spend more time being vigilant, so their effectiveness as foragers is reduced. Degus are prone to diabetes due to their divergent insulin structure.
Unlike other octodontids, degus are diurnal, and they have good vision. Their retinas include rod cells and two types of cone cell, one of which has its peak sensitivity in the ultraviolet region 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.
Photo by Brian Gratwicke