Yonenaga's Atlantic spiny-rat (''Trinomys yonenagae'') or torch-tail spiny rat is a spiny rat

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 ...

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 else ...

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 ...

. Locally, it is known as ''rabo de facho''. Named for Yatiyo Yonenaga-Yassuda, a cytogenetics researcher, it is considered an endangered species due to its highly restricted distribution and ongoing habitat loss. Genetic evidence shows that it diverged from its closest living relative, the hairy Atlantic spiny rat, around 8.5 million years ago, during the Late

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

Description

This is a comparatively small spiny rat, with an average head and body length of and a tail that averages long. It has large hind feet which, together with the long tail, are likely related to the fact that it mainly moves by hopping. The ears are also unusually large, as are the bony structures surrounding the inner ear. The fur is near-white on the underparts, but is otherwise grey in infants, changing to a richer brown colour as the animal reaches adulthood. Despite the name, the fur is mostly soft, although there are longer, flexible, dark-coloured bristles scattered across the body that correspond to the spines on most other spiny rats. An enlarged and modified

sebaceous gland A sebaceous gland is a microscopic exocrine gland in the skin that opens into a hair follicle to secrete an oily or waxy matter, called sebum, which lubricates the hair and skin of mammals. In humans, sebaceous glands occur in the greatest nu ...

is present near the anus, and produces a secretion described as having a " tutti-frutti-like" odour.

Distribution and habitat

Yonenaga's Atlantic spiny rat is known only from an approximately stretch of the west bank of the São Francisco River in

Bahia Bahia ( , , ; meaning "bay") is one of the 26 states of Brazil, located in the Northeast Region of the country. It is the fourth-largest Brazilian state by population (after São Paulo, Minas Gerais, and Rio de Janeiro) and the 5th-largest b ...

state, Brazil. This region is covered by sandy dunes on the border between the

cerrado The ''Cerrado'' (, ) is a vast ecoregion of tropical savanna in eastern Brazil, particularly in the states of Goiás, Mato Grosso do Sul, Mato Grosso, Tocantins, Minas Gerais, and the Federal District. The core areas of the Cerrado biome are the ...

and

caatinga Caatinga (, ) is a type of semi-arid tropical vegetation, and an ecoregion characterized by this vegetation in interior northeastern Brazil. The name "Caatinga" is a Tupi word meaning "white forest" or "white vegetation" (''caa'' = forest, v ...

habitats of eastern Brazil. It is considered a semi-arid habitat, with the sparse local plant life dominated by cactuses and bromeliads.

Behaviour

Despite living in a hot, dry, and sandy environment, Yonenaga's Atlantic spiny rat has few of the anatomic and physiologic adaptations expected of a desert-dwelling animal and instead relies on its behaviour to avoid the worst of the local conditions. It is nocturnal, and unlike other, closely related, spiny rats, digs burrows in which it spends the day. The burrows are shared communally, typically located in valleys between sand dunes where plants can provide local shade, and may extend below the surface. They are omnivorous, eating some insects, but primarily feeding on the local vegetation, including araçá-boi fruit, from which they obtain much of their water. Each burrow system is shared by up to eight adults, plus a variable number of young. The species does not appear to be territorial, and multiple females living in the same burrow raise young simultaneously. While aggression between neighbours is occasionally seen, most social behaviours are affiliative, including grooming, nose-to-nose or nose-to-ear rubbing and huddling. Even when intruders of the same species enter the burrow system, aggression is limited, and the individuals are more likely to huddle together than to fight. As vision is limited in their environment, in addition to vocal communication and drumming with their feet as warning signals, they rely on scents from anal glands to provide cues to identify and discern intentions of other rodents in the colony.

Reproduction

Yonenaga's Atlantic spiny rat breeds throughout the year, although young born during the dry season are much less likely to survive.

Courtship Courtship is the period wherein some couples get to know each other prior to a possible marriage. Courtship traditionally may begin after a betrothal and may conclude with the celebration of marriage. A courtship may be an informal and private m ...

involves foot-stamping, calls, and neck-biting by the males. The species is thought to be monogamous, but individuals of both sexes have been recorded helping to care for young that are not their biological offspring within the communal burrows.

Pregnancy Pregnancy is the time during which one or more offspring develops (gestation, gestates) inside a woman, woman's uterus (womb). A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occur ...

lasts for three months, and typically results in the birth of two young. The young are born with fine grey fur, with their eyes open and already able to move around. Sexual maturity occurs between three and four months of age, and the young may remain in the burrow of their birth well into adulthood, rather than dispersing to establish a new colony. In captivity they have been reported to live for up to 13 years, unusually long for a rodent of their size.

References

{{Taxonbar, from=Q686037 Trinomys Rodents of South America Mammals of Brazil Endemic fauna of Brazil Mammals described in 1995