Nilopegamys
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The Ethiopian amphibious rat, also known as the Ethiopian water mouse (''Nilopegamys plumbeus''), is an
insectivorous A robber fly eating a hoverfly An insectivore is a carnivorous animal or plant which eats insects. An alternative term is entomophage, which can also refer to the human practice of eating insects. The first vertebrate insectivores we ...
and
semiaquatic In biology, being semi-aquatic refers to various macroorganisms that live regularly in both aquatic and terrestrial environments. When referring to animals, the term describes those that actively spend part of their daily time in water (in ...
species of
rodent Rodents (from Latin , 'to gnaw') are mammals of the Order (biology), order Rodentia ( ), which are characterized by a single pair of continuously growing incisors in each of the upper and Mandible, lower jaws. About 40% of all mammal specie ...
in the
monotypic In biology, a monotypic taxon is a taxonomic group (taxon) that contains only one immediately subordinate taxon. A monotypic species is one that does not include subspecies or smaller, infraspecific taxa. In the case of genera, the term "unisp ...
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
''Nilopegamys'' of the family
Muridae The Muridae, or murids, are either the largest or second-largest family of rodents and of mammals, containing approximately 870 species, including many species of mice, rats, and gerbils found naturally throughout Eurasia, Africa, and Australia. ...
. There has only been one known specimen. It was found along the Lesser Abay River near its source at an altitude of 2600 m in the highlands of northwestern
Ethiopia Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...
in 1928. ''N. plumbeus'' is considered to be the most aquatically adapted African murid; its unusually large brain is thought to be one consequence of this lifestyle. The species is considered to be
critically endangered An IUCN Red List critically endangered (CR or sometimes CE) species is one that has been categorized by the International Union for Conservation of Nature as facing an extremely high risk of extinction in the wild. As of December 2023, of t ...
or possibly
extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...
, since its habitat has been severely damaged by
overgrazing Overgrazing occurs when plants are exposed to intensive grazing for extended periods of time, or without sufficient recovery periods. It can be caused by either livestock in poorly managed agricultural applications, game reserves, or nature ...
and monoculture.


Distribution and discovery

In late March 1928, the Ethiopian amphibious rat was cataloged for the first time. The specimen was discovered in a trap set by Wilfred H. Osgood, and was unlike any African rat he had seen before. The rat showed multiple adaptations to aquatic life which is uncommon for rats in Africa. Aquatic rats have been observed in South America but never before in east Africa. The Ethiopian amphibious rat has been spotted very few times in the wild. It has been sighted in the Ethiopian highlands in their wetland areas. The single found specimen was located near the Lesser Abay River in central Ethiopia. This rat is listed as critically endangered but many researchers studying the rodent fear it is already extinct due to two failed attempts to locate and track the rat.


Anatomy

''Nilopegamys plumbeus'' is specifically adapted to live near or in close contact with water. There are other rodents adapted to live in wetlands such as
marsh rice rat The marsh rice rat (''Oryzomys palustris'') is a semiaquatic North American rodent in the family Cricetidae. It usually occurs in wetland habitats, such as swamps and salt marshes. It is found mostly in the eastern and southern United States, f ...
or the
European water vole The European water vole (''Arvicola amphibius'') or northern water vole is a semi-aquatic rodent. It is often informally called the water rat, though it only superficially resembles a true rat. Water voles have rounder noses than rats, deep bro ...
. Out of all other African aquatic rodents however, the Ethiopian amphibious rat has the most extreme adaptations to its environment. They have a pair of adapted “waders” on their feet recognizable as webbing. Since N. plumbeus is so specifically adapted to its environment it makes living elsewhere very difficult. This is why scientists think that with the degradation of its habitat, N. plumbeus is now likely extinct. The rat belongs to the family Muridae and has the largest cranial capacity of any African muroid ever sampled. They also have very large brains compared to their body size and given the average brain size of aquatic rodents.


Status


Threats

The main reason for the population decline of the Ethiopian amphibious rat is habitat loss. Although not much research has been done on the preexisting population size of this rat species, it can be said the population has declined drastically with the destruction of its habitat. The leading cause for the destruction of Ethiopian highland, wetlands is loss to livestock grazing. Their habitat is almost completely destroyed due to this clearing for grazing and there is little being done to protect it. Ranching has also contributed to this habitat loss but not to the same scale.


Conservation & further knowledge

At the time there is not much in place in terms of conservation for the Ethiopian amphibious rat. They are considered critically endangered by the IUCN red list and even possibly extinct. There is also very little research that has been done on this species. Currently, East African highland small mammals are being studied by Julian Kerbis Peterhans at the Field Museum in Chicago Illinois, USA. Almost all that is known about this species is taken from a single study that was conducted in the 1920s. More research about this species, its habits, and its environment are needed.


References


External links


Mammal Species of the World
on
Bucknell University Bucknell University is a Private college, private Liberal arts colleges in the United States, liberal-arts college in Lewisburg, Pennsylvania, United States. Founded in 1846 as the University at Lewisburg, it now consists of the College of Arts a ...
website
Scientific Illustration
on
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{{Taxonbar, from=Q257684 Endemic fauna of Ethiopia Old World rats and mice Mammals of Ethiopia Mammals described in 1928 Taxonomy articles created by Polbot