{{Short description|Species of rodent}} {{good article}} {{Speciesbox | name = Mountain degu | image = Octodontomys gliroides 238516748.jpg | image_caption = Humahuaca Department, Argentina | status = LC | status_system = IUCN3.1 | status_ref = <ref name="iucn status 11 November 2021">{{cite iucn |author=Weksler, M. |date=2016 |title=''Octodontomys gliroides'' |volume=2016 |article-number=e.T15091A22240265 |doi=10.2305/IUCN.UK.2016-2.RLTS.T15091A22240265.en |access-date=11 November 2021}}</ref> | genus = Octodontomys | parent_authority = Palmer, 1903 | species = gliroides | authority = (Gervais & d'Orbigny, 1844) | range_map = Octodontomys gliroides range.svg | range_map_caption = ''O. gliroides'' range | synonyms = {{plainlist| *''Octodon gliroides'' <small>Gervais & d'Orbigny, 1844</small> *''Neoctodon simonsi'' <small>O. Thomas, 1902</small>}} | synonyms_ref = <ref name="mdd" /> }}
The '''mountain degu''' ('''''Octodontomys gliroides'''''), also known as the '''Andean degu''', is a species of rodent in the family Octodontidae. It is the only species in the genus '''''Octodontomys'''''. It is a medium-sized rodent with long, silky grey-brown fur, large grey ears, and white-furred chin and underparts. It is found in the foothills of the Andes in Argentina, Bolivia and Chile, and closely resembles the mountain viscacha rat and viscacha rats in the genus ''Tympanoctomys'', all of which are found in Argentina. It is an herbivore, and eats grasses, leaves, bark, and cacti. The mountain degu gets most of its water from eating the tissues of prickly pear cactuses and cactuses in the genus ''Cereus''.
The mountain degu is a social animal, though not as much as the related common degu, and lives in family units of two to four individuals that share a burrow, play together, and take dust baths in turn with each other. Mountain degus have no special ability to dig with their claws, and their burrows are often short. They often make their homes in caves and under rocks. Members of a social group communicate through gurgles, twitters and squeaks. The mountain degu's closest relatives are the rodents in the genera ''Octodon'', ''Spalacopus'', and ''Aconaemys''.
Mountain degus have little impact on human society. They are a potential carrier of the parasitic species ''Trypanosoma cruzi'', which can cause Chagas disease in humans. They are also host to fleas and lice. The mountain degu population is not threatened by anything, and it can be found in some protected areas, leading the International Union for Conservation of Nature to classify it as a least-concern species.
== Taxonomy and etymology == The mountain degu was first described in 1844 as a member of the genus ''Octodon'', having been given the scientific name ''Octodon gliroides'' by the French naturalists Paul Gervais and Alcide d'Orbigny. The species name, ''gliroides'', was given due to the animal's similar appearance to that of a dormouse ({{lang|la|gliris}} in Latin).<ref>{{Cite journal|last1=Gervais |first1=P. |author-link1=Paul Gervais |last2=d'Orbigny |first2=A. |author-link2=Alcide d'Orbigny |date=1844 |title=M. Paul Gervais communique, au nom de M. Alc. d'Orbigny et au sien, la description d'une espèce nouvelle de Mammifères Rongeurs |language=fr |publisher=Société Philomatique de Paris |journal=Extraits des procès-verbaux des séances |issue=9 |page=22 |url=https://www.biodiversitylibrary.org/page/31084901#page/300/mode/1up |via=Biodiversity Heritage Library}}</ref> The etymology of the name ''gliroides'' comes from a combination of the Latin {{lang|la|gliris}}, {{gloss|dormouse}} with the Greek suffixes {{lang|el-la|-o}} and {{lang|el-la|eidos}}, which indicate "likeness of form".<ref name=etym>{{Cite journal|journal=Mastozoología Neotropical|volume=2 |issue=2 |pages=173–206|issn=0327-9383|title=The mammals of Argentina: an etymology|first1=Janet K. |last1=Braun |first2=Michael A. |last2=Mares|date=1995|url=https://vertebrados.wordpress.com/wp-content/uploads/2019/10/sarem_mastneotrop_2-2_05_braun_etymology.pdf}}</ref> The type locality where it was first identified is the Andes in La Paz, Bolivia.<ref name="mdd">{{Cite mdd|id=1001497|genus=Octodontomys|species=gliroides|access-date=August 28, 2025}}</ref>
''Octodontomys'', a genus created in 1903 by American zoologist Theodore Sherman Palmer, comes from the Ancient Greek {{lang|grc|ὀκτώ}} ({{lang|grc-la|oktṓ}}), meaning {{gloss|eight}}, {{lang|grc|ὀδούς}} ({{lang|grc-la|odoús}}), meaning {{gloss|tooth}}, and {{lang|grc|μῦς}} ({{lang|grc-la|mûs}}), meaning {{gloss|mouse}}.<ref name=etym/> The genus was created to replace the earlier-used name ''Neoctodon'', which was already in use as a genus of beetles from an 1892 work by entomologist Ernest Marie Louis Bedel.<ref>{{Cite journal|url=https://www.biodiversitylibrary.org/page/31479480#page/887/mode/1up |last1=Palmer |first1=T.S. |author-link1=Theodore Sherman Palmer |title=Some new generic names of mammals |journal=Science |volume=17 |date=1903 |issue=439 |page=873 |doi=10.1126/science.17.439.873.a |pmid=17740805 |via=Biodiversity Heritage Library}}</ref> The British zoologist Oldfield Thomas had used the name ''Neoctodon'' in his 1901 description of the mountain degu (as the new species ''Neoctodon simonsi'', named in honor of the collector Perry O. Simons),<ref name=Thomas1902>{{cite journal | journal=Proceedings of the Zoological Society of London | title=On Two new Genera of Rodents from the Highlands of Bolivia | volume=1902 | pages=114–117 | first=O. |last=Thomas |author-link=Oldfield Thomas |publisher=Academic Press, [etc.] | date= 1902 | doi=10.1111/j.1469-7998.1902.tb08209.x | url=https://www.biodiversitylibrary.org/part/118624 |via=Biodiversity Heritage Library}}</ref> which he corrected to the currently used name, ''Octodontomys gliroides'', in his 1913 article ''On small mammals collected in Jujuy by Señor E. Budin''.<ref>{{Cite journal|journal=Annals and Magazine of Natural History |title=On small mammals collected in Jujuy by Señor E. Budin |pages=136–143 |date=1913 |volume=11 |location=London |publisher=Taylor and Francis|first=O. |last=Thomas |author-link=Oldfield Thomas |issue=61 |doi=10.1080/00222931308693298 |url=https://www.biodiversitylibrary.org/page/18635704#page/155/mode/1up |via=Biodiversity Heritage Library}}</ref> Thomas noted that the species was "strikingly different" from members of ''Octodon'', and differentiated it based on its "paler colour, whiter belly, and longer, more bushy tail".<ref name=Thomas1902 />
The common name "degu" is first recorded from the period between 1835 and 1845, and originates from the Mapuche word {{Lang|arn|deuñ}}<ref>{{Cite Collins Dictionary|degu|access-date=2025-08-28}}</ref> or {{Lang|arn|dewit}}. Over time, the word changed through its use in Chilean Spanish. Recorded common names for the species include long-tailed octodon, brush-tailed vizcacha rat,<ref name="Perez2018801">{{Harvnb|Pérez|Díaz|2018|pp=80–81}}</ref> and Andean degu.<ref name="Rivera2016411">{{Harvnb|Rivera|Vianna|Ebensperger|Eduardo Palma|2016|p=411}}</ref>
== Phylogeny == The phylogeny and placement of ''O. gliroides'' in relation to other octodontids was originally unclear.<ref>{{Cite journal |last1=Verzi |first1=Diego H. |last2=Olivares |first2=A. Itatí |last3=Morgan |first3=Cecilia C. |last4=Álvarez |first4=Alicia |date=March 2016 |title=Contrasting Phylogenetic and Diversity Patterns in Octodontoid Rodents and a New Definition of the Family Abrocomidae |url=http://link.springer.com/10.1007/s10914-015-9301-1 |journal=Journal of Mammalian Evolution |language=en |volume=23 |issue=1 |pages=93–115 |doi=10.1007/s10914-015-9301-1 |issn=1064-7554|hdl=11336/43822 |hdl-access=free }}</ref> It was placed as the sole member of ''Octodontomys'' in 2005,<ref name="MSW3">{{MSW3 Hystricognathi | id = 13400376 | page = 1572 | heading = Genus ''Octodontomys''}}</ref> and a study of mitochondrial DNA across the species' range published in 2016 solidified ''Octodontomys'' as a monophyletic group, albeit one with two distinct lineages, one of which is distributed across Bolivia and northern Chile, the other restricted to Argentina.<ref name="Rivera2016415">{{Harvnb|Rivera|Vianna|Ebensperger|Eduardo Palma|2016|p=415}}</ref> These two lineages diverged roughly {{ma|0.69}}.<ref name="Rivera2016423">{{Harvnb|Rivera|Vianna|Ebensperger|Eduardo Palma|2016|p=423}}</ref> Compared to other rodents worldwide, ''Octodontomys'' has some similarities to the monophyletic dassie rat.<ref>{{Cite book|last1=Mares |first1=M.A. |first2=R.A. |last2=Ojeda |date=1982 |chapter=Patterns of diversity and adaptation in South American hystricognath rodents |pages=393–432 |title=Mammalian Biology in South America |editor-first1=M.A.|editor-last1= Mares |editor-first2=H.H. |editor-last2=Genoways |publisher=Pymatuning Laboratory of Ecology, University of Pittsburgh |chapter-url=https://www.researchgate.net/publication/256415173 |url=https://books.google.com/books?id=W2YlwQEACAAJ}}</ref><!--What these similarities are, it isn't stated in the paper or in later works that reference it.--> The mountain degu has a diploid chromosome number of 38 and a fundamental number of 64.<ref name=":1">{{Cite journal |last1=Honeycutt |first1=Rodney L |last2=Rowe |first2=Diane L |last3=Gallardo |first3=Milton H |date=2003-03-01 |title=Molecular systematics of the South American caviomorph rodents: relationships among species and genera in the family Octodontidae |url=https://www.sciencedirect.com/science/article/pii/S1055790302003688 |journal=Molecular Phylogenetics and Evolution |volume=26 |issue=3 |pages=476–489 |doi=10.1016/S1055-7903(02)00368-8 |pmid=12644405 |bibcode=2003MolPE..26..476H |issn=1055-7903|hdl=10533/174195 |hdl-access=free }}</ref> The 28S and 18S ribosomal RNA of the mountain degu have notably split or eliminated introns, a genetic feature shared only with the tuco-tucos.<ref>{{Cite journal |last=Melen |first=G. J. |date=1999-06-01 |title=Novel processing in a mammalian nuclear 28S pre-rRNA: tissue-specific elimination of an 'intron' bearing a hidden break site |url=http://emboj.embopress.org/cgi/doi/10.1093/emboj/18.11.3107 |journal=The EMBO Journal |volume=18 |issue=11 |pages=3107–3118 |doi=10.1093/emboj/18.11.3107 |pmc=1171392 |pmid=10357822}}</ref>
The following cladogram is adapted from work done by Rivera and colleagues in 2014.<ref>{{Cite journal |last1=Rivera |first1=Daniela S. |last2=Abades |first2=Sebastian |last3=Alfaro |first3=Fernando D. |last4=Ebensperger |first4=Luis A. |date=2014-10-31 |title=Sociality of Octodontomys gliroides and other octodontid rodents reflects the influence of phylogeny |url=https://academic.oup.com/jmammal/article-lookup/doi/10.1644/14-MAMM-A-057 |journal=Journal of Mammalogy |language=en |volume=95 |issue=5 |pages=968–980 |doi=10.1644/14-MAMM-A-057 |issn=0022-2372|hdl=10533/148512 |hdl-access=free }}</ref> The genus ''Octodontomys'' is considered, as of 2018, to be the most primitive among the octodontids. It is thought to have diverged from its sister clade, which includes the genera ''Octodon'', ''Spalacopus'', and ''Aconaemys'', at a point roughly {{ma|5|7}}. No fossils of ''O. gliroides'' are known, and all estimates of species divergence times are made based on genetic analyses.<ref name="Perez201877" /> {{clade |label1=Octodontidae |1={{clade |1={{clade |1=''Octomys'' |2={{clade |1=''Pipanacoctomys'' |2=''Tympanoctomys'' }} }} |2={{clade |1='''''Octodontomys gliroides''''' |2={{clade |1={{clade |1=''Octodon'' |2={{clade |1={{clade |1={{clade |1=''Spalacopus'' |2=''Aconaemys porteri'' }} }} |2={{clade |1=''Aconaemys fuscus'' |2=''Aconaemys sagei'' }} }} }} }} }} }} }}
==Description== [[File:NeoctodonSimonsiSmit.jpg|thumb|left|''O. gliroides'' illustration by Joseph Smit, 1902]] The mountain degu is a rodent of medium size with an adult length of {{convert|200|to|380|mm|in|0|abbr=on}}, including a tail of {{convert|100|to|190|mm|in|0|abbr=on}}, and a body weight in the range of {{convert|100|to|200|g|oz|0}}. Its hairs are long and silky. The upper surface is greyish-brown, the chin is pure white, and the underparts are white with a grey base to the hairs. There is a tuft of white hair in front of the large ears, which are clad in short grey hair. The slender tail is bi-coloured (dark above and pale below) and has a tuft of brown or ochre hairs at the tip. Juveniles have darker fur above and greyer underparts. Their tails are brownish with a dark brown or black tufted tip.<ref name=Patton>{{cite book|author1=James L. Patton|author2=Ulyses F. J. Pardiñas|author3=Guillermo D'Elía|title=Mammals of South America, Volume 2: Rodents|url=https://books.google.com/books?id=mbjnBgAAQBAJ&pg=PA1035|date=9 March 2015 |publisher=University of Chicago Press |isbn=978-0-226-16960-6 |pages=1035–1037|oclc=904333770}}</ref> It is similar in appearance to other rodents in the octodontid family, bearing the closest resemblance to the mountain viscacha rat (''Octomys mimax'') and the viscacha rats in the genus ''Tympanoctomys''. The mountain degu can be reliably distinguished from these rodents in that its molars are asymmetrical when occluded, while other octodontids display more of a fiugre-8 pattern.<ref name="Perez201875">{{Harvnb|Pérez|Díaz|2018|p=75}}</ref>
Mountain degus have a dental formula of {{DentalFormula|upper=1.0.1.3|lower=1.0.1.3|total=20}}, with two incisors, no canines, two premolars, and six molars on each side of their jaw for a total of 20 teeth.<ref name="Perez201877">{{Harvnb|Pérez|Díaz|2018|pp=77}}</ref> The mountain degu has some distinctive dental and skeletal traits, as its molariform (premolar and molar) teeth lack as many folds as are found in other octodontids. Additionally, the first molariform tooth is inclined backwards near the socket (in the alveolar portion). The mountain degu's auditory bullae (bone structures that enclose part of the ear canal) are on average {{convert|14.6|mm|abbr=on}} in diameter, being of medium size and slightly smaller than those found in other octodontids adapted to arid climates.<ref name="Perez201875" /> The incisors constantly grow throughout the mountain degu's life and are hypsodont,<ref name="Perez201876">{{Harvnb|Pérez|Díaz|2018|p=76}}</ref> adapted to consuming plenty of cellulose.<ref name="Perez201879">{{Harvnb|Pérez|Díaz|2018|p=79}}</ref>
==Distribution and habitat== This species is found in the mountainous areas of southwestern Bolivia, northwestern Argentina and northern Chile.{{Sfn|Ojeda|2016|page=548}} It has a wide altitudinal range, occurring at {{convert|200|to|300|m|ft|-1}} in Jujuy Province in Argentina, and up to {{convert|4400|m|ft|-2}} in Potosí Department in Bolivia.<ref name=Patton/>
As the only species of octodontid found in the higher parts of its range, it inhabits dry rocky areas with tall cacti, shrubs and herbs.<ref name=Patton/> It is found in both the Atacama Desert of Chile and the Puna grassland habitats of Bolivia,<ref name="Rivera2016411" /> and is especially well suited for xeric habitats within and east of the Andes mountain range.<ref name=":1" /> Populations of mountain degus are separated from each other by natural features such as unvegetated salt flats, rivers, mountains, and floodplains, with the major barriers between Argentinian populations and the populations found in Bolivia and Chile being the San Juan River<!--This river is intentionally a red link as the "Argentina" San Juan River is in a completely different location--> and high mountain ranges at the Chile-Argentina border.<ref name="Rivera20164202">{{Harvnb|Rivera|Vianna|Ebensperger|Eduardo Palma|2016|pp=420–422}}</ref>
==Behaviour and diet== [[File:Octodontomys gliroides 339329462 (crop-sharp).png|thumb|right|alt=A brown and gray rodent on a rock|A mountain degu near Yavi, Jujuy Province, Argentina]] The mountain degu is a nocturnal,<ref name="Rivera2016411" /> herbivorous rodent, being most active just after sunset.{{Sfn|Ojeda|2016|page=549}} It does not have any special adaptations of skull or limbs for tunnelling, but digs short burrows and lives under rocks and in caves. Its tail can be autotomised, and it can be used as a prop when climbing. It is a sociable animal and vocally communicates by means of a range of low, medium and high-pitched gurgles, twitters and squeaks,<ref name="Patton" /> similar to the common degu and various species in genus ''Cavia''.<ref>{{Citation |last1=Schleich |first1=Cristian E. |title=Acoustic Communication in Subterranean Rodents |date=2007 |work=Subterranean Rodents |pages=113–127 |editor-last=Begall |editor-first=Sabine |url=http://link.springer.com/10.1007/978-3-540-69276-8_10 |access-date=2025-01-10 |place=Berlin, Heidelberg |publisher=Springer Berlin Heidelberg |language=en |doi=10.1007/978-3-540-69276-8_10 |isbn=978-3-540-69275-1 |last2=Veitl |first2=Silke |last3=Knotková |first3=Ema |last4=Begall |first4=Sabine |editor2-last=Burda |editor2-first=Hynek |editor3-last=Schleich |editor3-first=Cristian E.|url-access=subscription }}</ref> Social groups of the mountain degu range from 2 to 4 individuals that share a burrow system together to rest and hide from predators. Female mountain degus have a smaller home range than that of males.{{Sfn|Ojeda|2016|pp=542-544}} The mountain degu is notably less social than the common degu. Family groups engage in play shortly after waking from sleep, with individuals locking incisors with and riding on each other.<ref name="Perez2018798">{{Harvnb|Pérez|Díaz|2018|pp=79–80}}</ref> Like other octodontids,<ref name="Patton" /> the mountain degu takes dust baths, with each member of a family unit taking turns at the same location.<ref name="Perez201879" />
The mountain degu feeds on the leaves and bark of shrubs, ''Acacia'' sheaths, and cactus fruits. It can obtain sufficient moisture from its food, particularly cactus, to satisfy its water requirements.<ref name="Patton" /> Much of the degu's water comes from the tissues of cacti in the genera ''Cereus'' and ''Opuntia''. Cacti are largely preferred during the winter, and in the summer, mountain degus are found to feed upon a mixture of plants that undergo crassulacean acid metabolism and cool season grasses.<ref name="Perez201879" />
Mountain degu young in various stages of development have been found in November, and pregnant females and young in both January and May. A gestation period of 100–109 days has been reported with a litter size of one to three pups. The pups are precocial when born, already having their eyes open and being well-furred.{{Sfn|Ojeda|2016|page=549}}
== Relationship with humans == The mountain degu hosts parasites that are infectious to humans, such as the Chagas disease–causing ''Trypanosoma cruzi''. It is also parasitized by bloodsucking fleas in genus ''Ectinorus'' and lice in the genera ''Ferrisella''. Otherwise, it has little to no societal impact, similar to other degus.{{Sfn|Ojeda|2016|pp=544-545}}
==Conservation== The mountain degu is common within its distribution<ref name="Perez201880">{{Harvnb|Pérez|Díaz|2018|p=80}}</ref> and has no known threats. The International Union for Conservation of Nature considers it to be a least-concern species because it is widely distributed, occurs in some protected areas, and can tolerate changes in its habitat. The mountain degu population is not declining at an appreciable rate, and there are no conservation actions being taken towards it.<ref name="iucn status 11 November 2021" />
==References== {{Reflist}}
===Sources=== * {{HMW2016 Volume 6|chapter=Family Octodontidae (Viscacha Rats, Degus, Rock Rats and Coruro) |first1=A.A. |last1=Ojeda |pages=536-551 }} * {{Cite journal |last1=Pérez |first1=M Julieta |last2=Díaz |first2=M Mónica |date=2018-09-17 |title=''Octodontomys gliroides'' (Rodentia: Octodontidae) |url=https://academic.oup.com/mspecies/article/50/963/74/5098445 |journal=Mammalian Species |language=en |volume=50 |issue=963 |pages=74–83 |doi=10.1093/mspecies/sey010 |issn=0076-3519|hdl=11336/87053 |hdl-access=free }} * {{Cite journal |last1=Rivera |first1=Daniela S. |last2=Vianna |first2=Juliana A. |last3=Ebensperger |first3=Luis A. |last4=Eduardo Palma |first4=R. |date=October 2016 |title=Phylogeography and demographic history of the Andean degu, ''Octodontomys gliroides'' (Rodentia: Octodontidae) |url=https://academic.oup.com/zoolinnean/article-lookup/doi/10.1111/zoj.12412 |journal=Zoological Journal of the Linnean Society |language=en |volume=178 |issue=2 |pages=410–430 |doi=10.1111/zoj.12412}} {{Octodontidae nav}} {{Taxonbar|from=Q615863}}
Category:Mammals described in 1844 Category:Mammals of Argentina Category:Mammals of Bolivia Category:Mammals of Chile Category:Mammals of the Andes Category:Octodontidae Category:Taxonomy articles created by Polbot Category:Taxa named by Paul Gervais Category:Taxa named by Alcide d'Orbigny