Delany's swamp mouse (Delanymys brooksi)

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Delany's swamp mouse, lateral view
IUCN Red List species status – Vulnerable VULNERABLE

Top facts

  • Delany's swamp mouse is one of the world's smallest rodents, measuring just 5 to 6 cm long.
  • Delany's swamp mouse is a very active climber, using its grasping tail for balance and support.
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Delany's swamp mouse fact file

Delany's swamp mouse description

KingdomAnimalia
PhylumChordata
ClassMammalia
OrderRodentia
FamilyNesomyidae
GenusDelanymys (1)

The only member of its genus, Delany’s swamp mouse (Delanymys brooksi) is the smallest member of the Nesomyidae family, and one of the smallest rodents in the world (3) (4) (5).

Delany’s swamp mouse is a very small climbing mouse with an extremely long tail and characteristically long hind feet (3). The pelage of this species is long and is typically slate-grey at the base of the hairs, and brown with a reddish-orange tinge towards the tips. The underside of Delany’s swamp mouse is pale yellow-brown to buff (2).

This species has long black guard hairs, which give it a darker colouration (3). The eyes of Delany’s swamp mouse are surrounded by short black hairs and there is a black patch on the nose, while a distinctive patch of pure white hairs is present on the throat (2).

Delany’s swamp mouse has large, round ears and its tail is longer than the combined head-and-body length. The tail is thin, almost hairless, and has scales forming ring-like patterns along its length (2) (3). The male Delany’s swamp mouse is slightly smaller than the female, and the young have brighter, hazel-coloured fur (3).

Also known as
Delany's mouse.
Size
Head-body length: 5 - 6 cm (2)
Tail length: 8 - 11 cm (2)
Weight
5.2 - 6.5 g (2)
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Delany's swamp mouse biology

The nocturnal Delany’s swamp mouse is extremely well adapted for climbing on grass and plant stems. Its feet are highly specialised, with long, spreading digits and numerous small, prominent tubercles on the palms and fingers which enable grasping and prevent slipping. The long, prehensile tail of Delany’s swamp mouse is used to provide balance and can even be curled around stems for additional support (1) (3).  Seeds make up the majority of this small rodent's diet (2) (4).

Little is known about the reproductive behaviour of Delany’s swamp mouse, although two pregnant females have been recorded with three embryos each, and one nest with four blind young has been found. This species constructs a small, round grass nest with two entrances, usually off the ground in a bush or other such vegetation (2).

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Delany's swamp mouse range

Delany’s swamp mouse is native to the Albertine Rift Valley in southwest Uganda, western Rwanda, Burundi and the extreme eastern Democratic Republic of the Congo (1).

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Delany's swamp mouse habitat

Delany’s swamp mouse is largely confined to high-altitude marshes within bamboo or montane forests, at elevations of 1,700 to 2,400 metres or higher (1). A few individuals have been found in non-marshy habitats, such as dense, grassy vegetation (3).

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Delany's swamp mouse status

Delany's swamp mouse is classified as Vulnerable (VU) on the IUCN Red List (1).

IUCN Red List species status – Vulnerable

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Delany's swamp mouse threats

The small geographic range and fragmented distribution of Delany’s swamp mouse make it very vulnerable to continuing decline. Habitat destruction, largely due to agriculture and the high human population density of the region, is one of the greatest reasons for this species’ decreasing population size (1).

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Delany's swamp mouse conservation

No specific measures are currently in place to conserve Delany’s swamp mouse, despite it being the only surviving member of its subfamily, Delanymyinae (4). Much of its highland habitat is in the Kahuzi-Biega National Park in the Democratic Republic of the Congo. However, the lowlands remain severely threatened (1).

The population numbers of Delany’s swamp mouse need to be researched and monitored. Studies into the range, biology, ecology, habitat status and threats to this species are also needed in order to inform any future potential conservation measures (1).

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Find out more

Find out more about Kahuzi-Biega National Park:

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Authentication

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:
arkive@wildscreen.org.uk

This species information was authored as part of the ARKive and Universities Scheme.
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Glossary

Genus
A category used in taxonomy, which is below ‘family’ and above ‘species’. A genus tends to contain species that have characteristics in common. The genus forms the first part of a ‘binomial’ Latin species name; the second part is the specific name.
Guard hairs
In some mammals, long, coarse hairs that protect the softer layer of fur below.
Montane forest
Forest occurring in mountains.
Nocturnal
Active at night.
Omnivore
An organism that feeds on both plants and animals.
Prehensile
Capable of grasping.
Subfamily
A taxonomic category below a family but above a genus; a sub-division of a family, containing genera which are different enough to warrant a minor separation from the rest of the family.
Tubercle
A small, rounded, wart-like bump on the skin or on a bone.
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References

  1. IUCN Red List (November, 2011)
    http://www.iucnredlist.org/
  2. Nowak, R.M. (1999) Walker's Mammals of the World. The Johns Hopkins University Press, Baltimore.
  3. Dieterlen, F. (2010) Pers. comm.
  4. Vaughan, T.A., Ryan, J.M. and Czaplewski, N.J. (2011) Mammology. James and Bartlett Publishers, LLC, Sudbury.
  5. Britannica Educational Publishing (2011) Rats, Bats, and Xenarthrans. Britannica Educational Publishing, New York.
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Image credit

Delany's swamp mouse, lateral view  
Delany's swamp mouse, lateral view

© Dr. Fritz Dieterlen

Dr. Fritz Dieterlen
1969-1999 Head of the Mammal Section. Retired in 1994, then working as Research Associate and Honorary Member up to present
Staatliches Museum für Naturkunde Stuttgart, Rosenstein 1
Stuttgart, D- 70191
Germany
Tel: 07158 / 3796
fdieterlen@t-online.de

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