Tuesday 21 May
In the News: First crane egg in the western UK in four centuries

What’s the World’s Favourite Species?
Find out here.| Kingdom | Animalia |
| Phylum | Chordata |
| Class | Mammalia |
| Order | Didelphimorphia |
| Family | Didelphidae |
| Genus | Marmosa (1) |
Only seven individuals of this small marsupial have ever been found, all from a small region of southern Peru (2) (3). Anderson’s mouse opossum is a Marmosa, or slender mouse opossum, named for their similarity in appearance to mice. The dark grey fur on the upper parts is relatively long and tipped with reddish-brown, whist the underparts are paler. The hair on the cheeks and chin is cream coloured, and prominent black rings surround the eyes (3). Anderson’s mouse opossum has large thin ears, providing acute hearing (4). The tail, which is longer than the head and body, is furry at the base, with bristles that become longer and more slender towards the tip (3). Each foot has five digits and the big toe on the hindfoot is opposable, which, along with its prehensile (grasping) tail, makes Anderson’s mouse opossums well-adapted for a life in the trees (4)
Anderson’s mouse opossum is known only from one individual collected in 1954 (3), and several more specimens caught in the late 1990s (2), and thus very little is known about the biology of this incredibly rare animal. However, much can be deduced from studies of closely related species. It is likely to be nocturnal, and spend most of its time in trees (1). Like all marsupials, gestation is probably short, with females’ giving birth to poorly developed young and most of the development taking place during lactation (4). It is likely that reproduction is similar to that of Marmosa robinsoni, which gives birth to 6 to 14 young after a gestation period of just 14 days. The tiny young, measuring only up to 12 millimetres, attach themselves to the mother’s mammae where they may remain for around 30 days (5). Unlike many marsupials, female mouse opossums do not possess a pouch to protect the young as they develop (4). The young are so un-developed their eyes do not open until 39 to 40 days. It is likely that the young are completely weaned after around 65 days, and they may have an incredibly short life span of only one year (5). Marmosa species build nests for shelter, or use abandoned bird nests, holes in trees, or banana stalks. These nest sites are unlikely to be permanent; rather, the opossum will use whatever site is available as the sun begins to rise (5). Like M. robinsoni, it is likely that Anderson’s mouse opossum is insectivorous, with fruit also playing an important role in the diet (5).
TopAnderson’s mouse opossum is known from only three localities, within a narrow strip along the base of the Andes, in Cusco, southern Peru (1) (2) (3).
TopLittle is known about the habitat requirements of this species, except that it has been found in lowland tropical rainforest, below 1,000 metres, often around bamboo thickets (2). It is thought that the species is arboreal (1) (3), but specimens were not found more than three metres above the ground (2).
TopClassified as Data Deficient (DD) on the IUCN Red List (1).
TopAnderson’s mouse opossum is particularly vulnerable due to its intrinsically small range, and presumed tiny population. Despite the isolation of the region in which the specimens were found, the habitat still faces a number of threats, including expanding agriculture, overgrazing and unsustainable timber extraction (6). Such threats are likely to impact greatly on this tree-dwelling species.
TopThere are no known conservation measures currently in place for Anderson’s mouse opossum. It has been proposed that surveys should be undertaken to establish this species’ population size and distribution (7), information that could then be used to implement appropriate conservation measures to protect this unique marsupial.
TopFor further information on Anderson’s mouse opossum see:
More »Related species
Image credit
© Sergio Solari, Field Museum of Natural History
Sergio Solari
ssolari@matematicas.udea.edu.co
Link to this photo
Embed this ARKive thumbnail link by copying and pasting the code below.
Terms of Use - The displayed thumbnail may be used as a link from your website to ARKive's online content for private, scientific, conservation or educational purposes only. It may NOT be used within Apps.
Read more about
MyARKive
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.