[EN] Octodon degus in the wild

The Octodon degus is an animal originating from Chile, little known until a few years ago. In order to find out more about our little friends, we must focus on their natural habitat and their behaviour in the wild. For some years now, scientists have been studying them to understand their features. Thanks to these precious information, we are able to better treat the degu in captivity.

History of Octodon degus

Dessin d'octodons

Illustration by Vurore

If the degu inhabits Chile for a long time, the scientist Juan Ignacio Molina was the first one to describe it in 1782 as Sciurus degus1. From the XIXth century onwards, new designations of Octodontidaes appear before G. R. Waterhouse names it Octodon degus in 1848. Albino degus are discovered in 1967 and other rare coat variations are then observed. In 1927, J. A. Wolffsohn introduces the Octodon degus clivorum as an altitude subspecies. However, it is not acknowledged and makes the Octodon degus considered as a monotypical species.

Only staring from the mid 20th century that the Octodon degus and other different kinds of degus are more widely studied on their geographical distribution (Osgood, 1943) or their anatomy (Mann, 1940)1. To date, the Octodon degus is subject to scientific researches, allowing then a better understanding of its species. The Octodon degus is thus observed for its diabetes sensivity and Alzheimer disease2 but also its complex social behaviour.

Geographical distribution

Répartition géographique des différentes espèces d'octodons.

Geographical distribution of the differents species of degus in Chile, from the Holocene to the present day.

Despite being an endemic species from Chile3, the Octodon degus actually inhabits a part of the Andean Cordillera. It can also be found in Argentina and other nearby countries. Other species of degus can be found in Chile. In the wild, they use to share their territories even though to date, no interspecies breeding was found. Though, we can note that the Octodon pacificus is the only one that cannot mingle with its peers, exclusively inhabiting an island. The degus are old inhabitants of Chile, indeed, carbon dated bones have been found in excavation sites. Thus allowing to prove that this rodent was present in Chile 200 years BC4.

Remaining the most commun mammal in central Chile5, because of human actvity, populations of degus tend to deplete6. Moreover, the Octodon pacificus, considered an extinct species in several regions would still be around thanks to a female corpse discovered on Mocha Island. Nevertheless, locals fighting rats and mice which are an invasive species, are using poison to exterminate them. This poison is responsible for the death of the aformentioned female, indicating that degus tend to eat it.

Habitat

Burrows

The degu is a diurnal animal and to a lesser extent sometimes twilight with activity peaks in the morning and evening. It lives in holes comprised of several tunnels and chambers as well as numerous entrances. These lairs are both refuges and living places, the very territory of each group1 often settled around bushes. We can also find piles of branches or cow dung allowing to camouflage trails.  They can be blocked by twings and other material in case of danger7.

Paradoxally, small mounds are built nearby some entrances of which the point is still unanswered. It could be a means for males to establish dominance on neighbor clans5. Destroyed mounds could make the individual who built it lose its social role, who has to rebuild it quickly.

As a very sociable rodent, it shares its burrow with other species , such as the Ctenomys8 or the Abrocoma bennettii4. This species could be parasite, because it is unable to live without the Octodon degus.

Predation

The Octodon degus is a small rodent subject to multiple dangers. Predators are plentiful in its habitat and have a strong impact on its population9 as well as its behaviour. We can mention the culpeo but also several birds such as the barn owl, the short-eared owl and the black-chested buzzard-eagle10. However, the Octodon degus is not an easy prey, because it adopts social behaviours to avoid predation11. It gathers then with some individuals, allowing a deeper surveillance12. Depending on the grass cover13 the degu will adapt to risks but it is also an inconvenient to its vision of its surroundings.

Behaviour

Social life

As an excellent docile rodent, the degu lives in a group comprised of some females and up to 2 males. It gathers in more important communities living side by side in their multiple burrows. The degu tends to migrate to other clans14 without being philopatric. Thus, communities might be unstable, changing regularly their members.

The degu is an animal est un animal with a lot of social behaviours and a full part “vocabulary” thanks to its cries. Very expressive, it knows Très expressif, it knows how to make itelf heard and communicates with its peers. Their vocalizations can be grouped in 15 separate categories15, each one having a defined fonction. Whether it is to warn about a danger, during fights between congeners, contacts between adults, young degus’ distress or telling an incoming happy event, these sounds are complex and most of them are not understood yet.

Not all interactions between degus are made with vocals. Most of them are made with mutual grooming. Acknowledgement with “kisses” is also one of the most observed behaviours in that species. Plus, degus also tend to chase each other, in a play or a confrontation purpose, climbing on top of each other (without mating) or sleeping in group. Generally, females are looking for more interactions, especially during lactation period16.

Food

The Octodon degus is a herbivore with folivore tendencies. It mainly eats leaves and plant stems. Although its diet remains diverse because it can climb trees so it has access to the bark and the fruits. Roots and seeds are also an important part of its diet. In that way, it could participate to the spread of multiple species thanks to their seeds17. From time to time, it can even be seen eating some insects. When looking for food, degus have to go out of their hole and go through a dangerous environment. In that way, the degu moves from area to area until resources are depleted (plants, bushes).

Breeding

Mating

The female degu gives birth twice a year in the wild, with an average of 5 babies by litter. Mating is encouraged by its circadian rhythm, so it depends on the brightness but is also affected by other parameters18. If Thomas Bridge (1843) first reported a biennial mating, G. W. Fulk (1975) proved that in its northern areas, birthing can be possible up to September, thus increasing the number of matings in the year. However, peaks of litters in the wild remain around summer with records between July and August. Among the rodents, it is the species that has the longest pregnancy. Indeed, it requires 90 days (3 months) to the female to give birth, or the equivalent of the cheetah19 or the panther!

Litters

Females can take care of several litters at once, without taking their age into account nor where they originate from20. But they know however how to recognize their own babies21. Though, fathers get involved with the babies, even though they seek for domination over them and limitate games22. Cases of infanticide for Octodons degus are nigh nonexistent in the wild23 but can sometimes be observed in captivity. Moreover, it is common to see a species of rodents sharing its burrow without disturbing the degus8.

Babies are born with their hair, their eyes almost open and start to walk after a couple of hours. With an average of 14 grams the first day, they are already capable, unlike racoons and pups, to control the temperature of their body. They are weaned after rougly 8 weeks and sexually active between 2 and 9 months depending on the individuals5.

Translation by Matthieu Selles.

Sources

  1. https://www.jstor.org/stable/3503820?seq=1[][][]
  2. https://www.sciencedirect.com/science/article/abs/pii/S016372581830041X[]
  3. https://www.britannica.com/animal/degu[]
  4. http://theses.vet-alfort.fr/telecharger.php?id=340[][]
  5. https://www.jstor.org/stable/3503820[][][]
  6. https://scielo.conicyt.cl/scielo.php?script=sci_arttext&pid=S0716-078X2003000300004[]
  7. https://onlinelibrary.wiley.com/doi/full/10.1111/j.1468-5584.2004.00257.x[]
  8. https://zslpublications.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-7998.1839.tb00010.x[][]
  9. https://link.springer.com/article/10.1007/BF00341311[]
  10. https://www.semanticscholar.org/paper/Notes-on-the-Activity%2C-Reproduction%2C-and-Social-of-Fulk/0bcc9459f89d8499f79d663ccee70321a6314e28[]
  11. https://academic.oup.com/jmammal/article-abstract/76/3/900/864741?redirectedFrom=fulltext[]
  12. https://onlinelibrary.wiley.com/doi/abs/10.1034/j.1600-0706.2002.980313.x[]
  13. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1439-0310.2005.01084.x[]
  14. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1439-0310.2009.01635.x[]
  15. https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.737.7291&rep=rep1&type=pdf[]
  16. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3914217/[]
  17. https://www.tandfonline.com/doi/abs/10.1080/01650529109360846[]
  18. https://www.frontiersin.org/research-topics/12583/octodon-degus-an-animal-model-that-benefits-translational-medicine[]
  19. https://fr.wikipedia.org/wiki/Gu%C3%A9pard#Reproduction_et_vie_sociale[]
  20. https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1439-0310.2006.01251.x[]
  21. https://www.semanticscholar.org/paper/Mother%E2%80%93offspring-recognition-in-communally-nesting-Jesseau-Holmes/7143737a9235520a98c265e034ec6ac156aaa04f[]
  22. https://onlinelibrary.wiley.com/doi/abs/10.1002/dev.420150309[]
  23. https://link.springer.com/article/10.1007/s102110000032[]

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