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Yonenaga's Atlantic spiny-rat
Conservation status
Endangered  (IUCN 3.1)
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Rodentia
Family:	Echimyidae
Subfamily:	Euryzygomatomyinae
Genus:	Trinomys
Species:	T. yonenagae
Binomial name
Trinomys yonenagae (Rocha, 1995)
Synonyms
Proechimys yonenagae Rocha, 1995

Yonenaga's Atlantic spiny-rat (Trinomys yonenagae) or torch-tail spiny rat is a spiny rat species endemic to Brazil. 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.

Description

This is a comparatively small spiny rat, with an average head and body length of 16 centimetres (6.3 in) and a tail that averages 19 centimetres (7.5 in) 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 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 130 kilometres (81 mi) stretch of the west bank of the São Francisco River in Bahia state, Brazil. This region is covered by sandy dunes on the border between the cerrado and caatinga 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 15 metres (49 ft) 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 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 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

1. ^ Roach, N.; Naylor, L. (2016). "Trinomys yonenagae". IUCN Red List of Threatened Species. 2016: e.T136414A22212204. doi:10.2305/IUCN.UK.2016-2.RLTS.T136414A22212204.en. Retrieved 28 May 2021.
2. ^ da Rocha, P.L.B. (1995). "Proechimys yonenagae, a new species of spiny rat (Rodentia : Echimyidae) from fossil sand dunes in the Brazilian Caatinga". Mammalia. 59 (4): 537–549. doi:10.1515/mamm.1995.59.4.537. S2CID 201093005.
3. Emmons, Louise H. (1990). Neotropical rainforest mammals : a field guide. Illustrations: Feer, François. Chicago: University of Chicago Press. ISBN 0-226-20716-1.
4. ^ Santos, J.W.A.; Lacey, E.A. (February 2011). "Burrow sharing in the desert-adapted torch-tail spiny rat, Trinomys yonenagae". Journal of Mammalogy. 92 (1): 3–11. doi:10.1644/09-MAMM-S-389.1.
5. ^ Manaf, Paulo; de Brito-Gitirana, Lycia; Oliveira, Elisabeth Spinelli (Jul 2003). "Evidence of chemical communication in the spiny rat Trinomys yonenagae (Echimyidae): Anal scent gland and social interactions". Canadian Journal of Zoology. 81 (7): 1138–43. doi:10.1139/z03-095.
6. Fabre, P.; Upham, N.S.; et al. (March 2017). "Mitogenomic phylogeny, diversification, and biogeography of South American spiny rats". Molecular Biology and Evolution. 34 (3): 613–633. doi:10.1093/molbev/msw261. PMID 28025278.
7. ^ Luchesi, Lilian; Cantano, L.M.R.; et al. (June 2019). "Trinomys yonenagae (Rodentia: Echimyidae)". Mammalian Species. 51 (971): 1–10. doi:10.1093/mspecies/sez001.
8. Gutiérrez, Eliécer E.; Marinho-Filho, Jader (January 2017). "The mammalian faunas endemic to the Cerrado and the Caatinga". ZooKeys (644): 105–157. doi:10.3897/zookeys.644.10827. PMC 5242261. PMID 28144187.
9. Alvares, Clayton Alcarde; Stape, José Luiz; Sentelhas, Paulo Cesar; de Moraes Gonçalves, José Leonardo; Sparovek, Gerd (2013). "Köppen's climate classification map for Brazil". Meteorologische Zeitschrift. 22 (6): 711–728. Bibcode:2013MetZe..22..711A. doi:10.1127/0941-2948/2013/0507.
10. da Rocha, P.L.B.; de Queiroz, L.P.; Pirani, J.R. (December 2004). "Plant species and habitat structure in a sand dune field in the Brazilian Caatinga: a homogeneous habitat harbouring an endemic biota". Brazilian Journal of Botany. 27 (4): 739–755. doi:10.1590/S0100-84042004000400013.
11. da Rocha, P.L.B.; Renous, S.; et al. (July 2007). "Evolution toward asymmetrical gaits in Neotropical spiny rats (Rodentia: Echimyidae): evidences favoring adaptation". Canadian Journal of Zoology. 85 (6): 709–717. doi:10.1139/Z07-049.
12. Marcomini, Monique; Oliveira, Elisabeth (August 2010). "Activity pattern of echimyid rodent species from the Brazilian Caatinga in captivity". Biological Rhythm Research. 34 (2): 157–166. doi:10.1076/brhm.34.2.157.14491. S2CID 84793518.
13. de Freitas, J.N.S.; da Silva Carvalho, L.A.; et al. (May 2009). "Affiliation in the social interactions in captivity of the torch tail rat, Trinomys yonenagae (Rodentia: Echimyidae)". Journal of Ethology. 28: 105–112. doi:10.1007/s10164-009-0161-0. S2CID 34200319.
14. de Freitas, J.N.S.; El-Hani, C.N.; da Rocha, P.L.B. (March 2008). "Affiliation in four echimyid rodent species based on intrasexual dyadic encounters: evolutionary implications". Ethology. 114 (4): 389–397. doi:10.1111/j.1439-0310.2008.01481.x.

• IUCN Red List endangered species
• Trinomys
• Rodents of Brazil
• Endemic mammals of Brazil
• Mammals described in 1995