The Brazilian arboreal mouse (''Rhagomys rufescens'') is a

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriate s ...

of the family

Cricetidae The Cricetidae are a family of rodents in the large and complex superfamily Muroidea. It includes true hamsters, voles, lemmings, muskrats, and New World rats and mice. At almost 608 species, it is the second-largest family of mammals, and has m ...

. It is found in the

Atlantic Forest The Atlantic Forest ( pt, Mata Atlântica) is a South American forest that extends along the Atlantic coast of Brazil from Rio Grande do Norte state in the northeast to Rio Grande do Sul state in the south and inland as far as Paraguay and th ...

of southeast

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

, often close to

bamboo Bamboos are a diverse group of evergreen perennial flowering plants making up the subfamily Bambusoideae of the grass family Poaceae. Giant bamboos are the largest members of the grass family. The origin of the word "bamboo" is uncertain, bu ...

thickets. It can be distinguished from '' Rhagomys longilingua'', the only other species in its

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

, by the absence of spines among the hair. Formerly believed to be extinct after no sightings were recorded for over 100 years, the species has since been found in four localities. However, it is nowhere common, and all of these are forest fragments, and ongoing deforestation threatens the species' survival. For these reasons, the

International Union for Conservation of Nature The International Union for Conservation of Nature (IUCN; officially International Union for Conservation of Nature and Natural Resources) is an international organization working in the field of nature conservation and sustainable use of natu ...

has assessed its conservation status as being " vulnerable".

Description

The Brazilian arboreal mouse is a small mouse with small rounded ears and

vibrissae Vibrissae (; singular: vibrissa; ), more generally called Whiskers, are a type of stiff, functional hair used by mammals to sense their environment. These hairs are finely specialised for this purpose, whereas other types of hair are coarser ...

(whiskers) long enough to reach the ears. The dorsal fur is reddish-brown which gradually fades to reddish-grey on the ventral surface. The hair is soft, and this distinguishes ''Rhagomys rufescens'' from the only other species in the genus, '' Rhagomys longilingua'', which has spines mixed in with the hairs. They also differ in certain skull characteristics, and their ranges do not overlap. The head-and-body length slightly exceeds the tail length. The tail is brownish and has small scales. It is sparsely clad in blackish hairs that get longer near the tip and form a tuft. The hind feet are broad with bare soles and fleshy plantar pads. The

hallux Toes are the digits (fingers) of the foot of a tetrapod. Animal species such as cats that walk on their toes are described as being '' digitigrade''. Humans, and other animals that walk on the soles of their feet, are described as being '' pl ...

(big toe) bears a nail rather than a claw, a unique characteristic of this genus. The female has three pairs of

mammary gland A mammary gland is an exocrine gland in humans and other mammals that produces milk to feed young offspring. Mammals get their name from the Latin word ''mamma'', "breast". The mammary glands are arranged in organs such as the breasts in primat ...

Distribution and habitat

''R. rufescens'' was first described in 1886 from

Rio de Janeiro State Rio de Janeiro () is one of the 27 federative units of Brazil. It has the second largest economy of Brazil, with the largest being that of the state of São Paulo. The state, which has 8.2% of the Brazilian population, is responsible for 9.2% of ...

in Brazil but it has not been found in that locality for over one hundred years and was believed to be

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

. However, it has now been found in four other localities in Brazil, near

Ubatuba Ubatuba is a Brazilian municipality, located on the southeast coast, in the state of São Paulo. It is part of the Metropolitan Region of Vale do Paraíba e Litoral Norte. The population is 92,819 (2021 est.) in an area of 723.88 km², of whi ...

São Paulo State SAO or Sao may refer to: Places * Sao civilisation, in Middle Africa from 6th century BC to 16th century AD * Sao, a town in Boussé Department, Burkina Faso * Saco Transportation Center (station code SAO), a train station in Saco, Maine, U.S ...

, including in Pincinguaba State Park, and near Viçosa in Minas Gerais State. It typically lives in Atlantic forest, often among bamboos, and also in modified forest habitats.

Ecology

Little is known about this species and its natural history. Several specimens were caught in

pitfall trap A pitfall trap is a trapping pit for small animals, such as insects, amphibians and reptiles. Pitfall traps are a sampling technique, mainly used for ecology studies and ecologic pest control. Animals that enter a pitfall trap are unable to esca ...

s sunk in the ground, but it is thought that it is an arboreal rodent, or one that scrambles among the undergrowth, because of the

morphology Morphology, from the Greek and meaning "study of shape", may refer to: Disciplines *Morphology (archaeology), study of the shapes or forms of artifacts *Morphology (astronomy), study of the shape of astronomical objects such as nebulae, galaxies, ...

of its feet. Examination of the stomach contents of one individual that was caught showed that it had eaten several species of

ant Ants are eusocial insects of the family Formicidae and, along with the related wasps and bees, belong to the order Hymenoptera. Ants evolved from vespoid wasp ancestors in the Cretaceous period. More than 13,800 of an estimated total of 22 ...

References

{{Taxonbar, from=Q1765813 Rhagomys Mammals described in 1886 Taxa named by Oldfield Thomas Endemic fauna of Brazil