Sunday 19 May
Santiago Galapagos mouse (Nesoryzomys swarthi)
What’s the World’s Favourite Species?Find out here.
Santiago Galapagos mouse fact file
- Find out more
- Print factsheet
Santiago Galapagos mouse description
First described in 1906 from the island of Santiago in the Galapagos, the Santiago Galapagos mouse was believed extinct until its rediscovery in 1997 (2) (3) (4). Previously, it was assumed that this and other endemic ‘rice rats’ in the Galapagos could not coexist with the introduced black rats which infest the islands (3), making this species’ rediscovery all the more remarkable. One of the few native land mammals to inhabit the Galapagos Islands, the Santiago Galapagos mouse has harsh, brownish fur, lighter on the underparts, and a long, sparsely-haired tail (3). It is the largest of the Galapagos rice rat species, and is sexually dimorphic, the male being larger than the female (4).
- Also known as
- Santiago rice rat. Top
Charles Darwin Foundation:
Galapagos Conservation Trust:
- A species or taxonomic group that is only found in one particular country or geographic area.
- Active at night.
- Mating system in which males have more than one female partner.
- Mating with more than one individual without forming any permanent bonds.
- Sexual dimorphism
- When males and females of the same species differ in appearance.
- Animal with a backbone.
- IUCN Red List (May, 2009)
- Dowler, R.C., Carroll, D.S. and Edwards, C.W. (2000) Rediscovery of rodents (Genus Nesoryzomys) considered extinct in the Galápagos Islands. Oryx, 34(2): 109 - 117.
- Charles Darwin Foundation (May, 2009)
- Macdonald, D.W. (2006) The Encyclopedia of Mammals. Oxford University Press, Oxford.
- Harris, D.B., Gregory, S.D. and Macdonald, D.W. (2006) Space invaders? A search for patterns underlying the coexistence of alien black rats and Galápagos rice rats. Oecologia, 149: 276 - 288.
- Galapagos Conservation Trust: Charles Darwin Research Station News Bulletin, November 2005 (May, 2009)
- Nowak, R.M. (1991) Walker’s Mammals of the World. The Johns Hopkins University Press, Baltimore and London.
- Harris, D.B. and Macdonald, D.W. (2007) Population ecology of the endemic rodent Nesoryzomys swarthi in the tropical desert of the Galápagos Islands. Journal of Mammalogy, 88(1): 208 - 219.
- Gregory, S.D. and Macdonald, D.W. (2009) Prickly coexistence or blunt competition? Opuntia refugia in an invaded rodent community. Oecologia, 159: 225 - 236.
- Harris, D.B. and Macdonald, D.W. (2007) Interference competition between introduced black rats and endemic Galápagos rice rats. Ecology, 88(9): 2330 - 2344.
- Wildlife Conservation Research Unit, University of Oxford (May, 2009)
- view the contents of, and Material on, the website;
- download and retain copies of the Material on their personal systems in digital form in low resolution for their own personal use;
- teachers, lecturers and students may incorporate the Material in their educational material (including, but not limited to, their lesson plans, presentations, worksheets and projects) in hard copy and digital format for use within a registered educational establishment, provided that the integrity of the Material is maintained and that copyright ownership and authorship is appropriately acknowledged by the End User.
Santiago Galapagos mouse biology
Little is known about the Santiago Galapagos mouse. It is believed to be nocturnal and terrestrial, living in burrows or rock crevices beneath bushes (1) (7), and may feed on grasses, fruits and seeds (3), and possibly some insects. Breeding occurs in the wet season, with pregnancy peaking in April, and the mating system appears to be promiscuous or polygynous. The young grow and develop slowly, and do not breed in the first year. Lifespan may be over two years (8). It is thought that the species’ relatively high survival and low reproductive rate may be adaptations to the unpredictable and ephemeral resources found in the Galapagos arid zone (4) (8).Top
Santiago Galapagos mouse rangeTop
Santiago Galapagos mouse habitatTop
Santiago Galapagos mouse status
Classified as Vulnerable (VU) on the IUCN Red List (1).Top
Santiago Galapagos mouse threats
The endemic rice rats have lost more species than any other group of vertebrates in the Galapagos, a decline believed to have been caused by introduced black rats (Rattus rattus), mice and feral cats (2) (3) (4) (5). The Santiago Galapagos mouse is the only one of the remaining species to occur alongside the black rat, which is known to have been present on Santiago since at least 1835, when Charles Darwin collected it during his visit to the island (2) (5). However, the coexistence of the two species is not stable. The black rat is larger, more aggressive and more dominant than the Santiago Galapagos mouse, with studies showing it displaces the smaller endemic species at food sources and has a negative impact on its population (4) (5).
Although two new populations of the Santiago Galapagos mouse were found in 2005 (1) (6), the species has been lost from parts of its historical range (5), and its small, highly restricted population apparently owes its continued survival to areas of Opuntia cacti (4). These cacti provide a rich source of food, water and nesting sites, particularly in the dry season when alternative resources are hard to find. However, the black rat appears not to feed on Opuntia, giving the Santiago Galapagos mouse a vital refuge from competition (4) (5) (9). In addition, the particularly arid local climate at this site allows the more drought-resistant Santiago Galapagos mouse to survive while the black rat population crashes during years of drought (4) (10). The biggest threat to the Santiago Galapagos mouse now comes from climate change, with a predicted increase in rainfall that could lead to increased vegetation and food supply, allowing black rat populations to explode, while at the same time decimating the Opuntia vegetation on which the Santiago Galapagos mouse now depends (4) (10).Top
Santiago Galapagos mouse conservation
The rediscovery of the Santiago Galapagos mouse has raised hopes of finding populations of other rice rat species previously thought to be extinct (2). Further searches for this species on Santiago Island have also been recommended (6). Projects are currently underway to monitor and study the Santiago Galapagos mouse, and an action plan for the species has been proposed (11), as well as the possibility of establishing a captive population (2). The Charles Darwin Foundation and visiting scientists have been working with the Galapagos National Park Service to perform experimental black rat removal on Santiago, and black rat eradication has already begun on surrounding islets, which may be used as possible refuges for the Santiago Galapagos mouse (3) (11). Eradication of feral cats also needs to be undertaken (3), and the house mouse (Mus musculus) monitored to ensure the population of this introduced species does not increase in the absence of the black rat (10).Top
Find out more
To find out more about rice rats, and about conservation in the Galapagos Islands, see:
This information is awaiting authentication by a species expert, and will be updated as soon as possible. If you are able to help please contact:
More »Related species
Play the Team WILD game
MyARKive offers the scrapbook feature to signed-up members, allowing you to organize your favourite ARKive images and videos and share them with friends.
Terms and Conditions of Use of Materials
Copyright in this website and materials contained on this website (Material) belongs to Wildscreen or its licensors.
Visitors to this website (End Users) are entitled to:
End Users shall not copy or otherwise extract, alter or manipulate Material other than as permitted in these Terms and Conditions of Use of Materials.
Additional use of flagged material
Green flagged material
Certain Material on this website (Licence 4 Material) displays a green flag next to the Material and is available for not-for-profit conservation or educational use. This material may be used by End Users, who are individuals or organisations that are in our opinion not-for-profit, for their not-for-profit conservation or not-for-profit educational purposes. Low resolution, watermarked images may be copied from this website by such End Users for such purposes. If you require high resolution or non-watermarked versions of the Material, please contact Wildscreen with details of your proposed use.
Creative commons material
Certain Material on this website has been licensed to Wildscreen under a Creative Commons Licence. These images are clearly marked with the Creative Commons buttons and may be used by End Users only in the way allowed by the specific Creative Commons Licence under which they have been submitted. Please see http://creativecommons.org for details.
Any other use
Please contact the copyright owners directly (copyright and contact details are shown for each media item) to negotiate terms and conditions for any use of Material other than those expressly permitted above. Please note that many of the contributors to ARKive are commercial operators and may request a fee for such use.
Save as permitted above, no person or organisation is permitted to incorporate any copyright material from this website into any other work or publication in any format (this includes but is not limited to: websites, Apps, CDs, DVDs, intranets, extranets, signage, digital communications or on printed materials for external or other distribution). Use of the Material for promotional, administrative or for-profit purposes is not permitted.