The Ankarana Special Reserve tufted-tailed rat (''Eliurus carletoni'') (synonymous with ''Eliurus'' sp. SAJ-2009a) is a species of

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 ...

in the family

Nesomyidae The Nesomyidae are a family of African rodents in the large and complex superfamily Muroidea. It includes several subfamilies, all of which are native to either continental Africa or to Madagascar. Included in this family are Malagasy rodents, ...

. It was first described in 2009. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Madagascar Madagascar (; mg, Madagasikara, ), officially the Republic of Madagascar ( mg, Repoblikan'i Madagasikara, links=no, ; french: République de Madagascar), is an island country in the Indian Ocean, approximately off the coast of East Africa ...

, in the

Ankarana Special Reserve Ankarana Special Reserve in northern Madagascar was created in 1956. It is a small, partially vegetated plateau composed of 150-million-year-old middle Jurassic limestone. With an average annual rainfall of about , the underlying rocks have been e ...

Distribution and morphology

''E. carletoni'' is a relatively new species restricted to Northern Madagascar. The species was named in honor of Dr. Michael Carleton of the

National Museum of Natural History The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. In 2021, with 7 ...

for his substantial influence in the study of rodent systematics and of rodents native to the island of Madagascar. Currently, ''E. carletoni'' is endemic to the Réserve Spéciale (RS) d’Ankarana. Madagascar is widely known for its unique biomes and biota. The genus ''Eliurus'' is part of the order Rodentia and the family Nesomyidae. ''E. carletoni'' can be characterized by the following: Overall, the texture of body hair is soft and fine. Cover hairs of the dorsum are bi-colored (proximal two-thirds is dark brown, and the distal one-third is a medium buff). The guard hairs, which have the primary role of protecting the rest of the

pelage Fur is a thick growth of hair that covers the skin of mammals. It consists of a combination of oily #Guard hair, guard hair on top and thick #Down hair, underfur beneath. The guard hair keeps moisture from reaching the skin; the underfur acts as ...

from abrasion and moisture, show characteristic colors of dark brown to black. The belly of ''E. carletoni'' is characteristically white. ''E. carletoni'' has a somewhat large cranium, a relatively short rostrum, moderately long molar rows, and a palatine process that is shorter and stouter in comparison to others within the genus. Likewise, the enamel of the anterior portion of the incisors is a dull yellow-orange color. ''E. carletoni'' exhibits a unicolor brown tail, which is also characteristic of others in the genus.

Habitat

Members of the genus have been found to inhabit all the natural forest types on the island from humid forestation on the eastern side of the island to the xerophytic spiny bushes located in the southwest portion of the island. ''E. carletoni'' can be found specifically in the dry deciduous forests of Madagascar. Members of the species are known to inhabit forested areas resting on limestone outcrops. In Northern Madagascar, there are three regions of interest where ''E. carletoni'' live: the

Loky-Manambato Loky-Manambato is a protected area in northern Madagascar. The protected area covers 2484.09 km2,UNEP-WCMC (2022)Protected Area Profile for Loky Manambatofrom the World Database on Protected Areas. Accessed 18 September 2022. and includes a block ...

, Ankarana, and Analmerana. Ankarana and Analamerana differ from Loky-Manambato in that they are solely areas of

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

. Loky-Manambato is highly heterogenous in its presence of large forested areas and many river systems. In fact, the Loky-Manambato region is so diverse in its make up that areas of dry forest and humid forest occur closely together only to be separated by mountains and rivers in some cases. The

topographic Topography is the study of the forms and features of land surfaces. The topography of an area may refer to the land forms and features themselves, or a description or depiction in maps. Topography is a field of geoscience and planetary scie ...

distribution of the region includes elevations ranging from sea level up to 1170 meters. Though the Loky-Manambato region is very diverse, as previously stated, ''E. carletoni'' is found to only inhabit the dry forest areas.

Reproduction and evolution

Little is known about the reproductive behavior and seasonality of ''E. carletoni''. To this point, only a few observations have been made regarding these behaviors. We learn from a study done by Goodman et al. that in early January, some individuals can be found in reproductive condition while others are not. Some males show no scrotal testes while others show large scrotal testes and convoluted

epididymides The epididymis (; plural: epididymides or ) is a tube that connects a testicle to a vas deferens in the male reproductive system. It is a single, narrow, tightly-coiled tube in adult humans, in length. It serves as an interconnection between the ...

. Likewise, on another occasion in early April, one male was found in non-reproductive condition while another was found with partially scrotal testes and slightly convoluted epididymides. Within this same period, multiple females were found with large

mammae 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 ...

all without embryos present, but one with placental scarring. As we learn with many species, evolution can be driven by a variety of factors. For some, it is competition of various types, and for others, it is a matter of adapting to the changing climate. We learn in the case of ''E. carletoni'' that a

bottleneck Bottleneck literally refers to the narrowed portion (neck) of a bottle A bottle is a narrow-necked container made of an impermeable material (such as glass, plastic or aluminium) in various shapes and sizes that stores and transports liquids ...

event occurred between 18,750 and 7,500 years ago, mainly due to the complexity within the Loky-Manambato region. Clearly, deforestation and other

anthropogenic Anthropogenic ("human" + "generating") is an adjective that may refer to: * Anthropogeny, the study of the origins of humanity Counterintuitively, anthropogenic may also refer to things that have been generated by humans, as follows: * Human im ...

forest fragmenting will cause stress on a species to change. However, historical demographic analyses have proposed that the current genetic patterns we see in ''E. carletoni'' are occurring due to prehuman vegetational shifts because of the contraction and fragmentation of dry forests.

References

{{Taxonbar, from=Q4765992 Eliurus Mammals described in 2009