Trinomys yonenagae
Creators: name: Don E. Wilson
name: Thomas E. Lacher, Jr
name: Russell A. Mittermeier
Publisher: name: Lynx Edicions
Year: 2016
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Mammalia
Rodentia
Echimyidae
Trinomys
Trinomys yonenagae

description: 17.
Yonenaga’s Spiny-rat
Trinomys yonenagae
French: Rat-épineux d'Yonenaga / German: Yonenaga-Atlantikstachelratte / Spanish: Rata espinosa de Yonenaga
Other common names: Yonenaga's Atlantic Spiny-rat, Torch-tail Spiny-rat
Taxonomy. Proechimys yonenagae da Rocha, 1995,
“Ibiraba, Bahia, Brazil (10°48’S, 42°50'W).”
This species is monotypic.
Distribution. E Brazil, left bank of the middle Rio Sao Francisco in NW Bahia State.
Descriptive notes. Head-body 141-195 mm, tail 169-225 mm. No specific data are available for body weight. Yonenaga’s Spiny-rat is small to medium-sized, with generally paler dorsum than congeners, pale cinnamon mixed with darker hairs on mid-dorsum, gradually lightening on sides, and only slightly contrasting with white venter. Tail is markedly bicolored, brownish above and white below, and long, averaging 120% of head-body length. Tail terminates in distinctively long hairy pencil, with hairs extending more than 30 mm beyondits tip. Pelage overall is relatively soft, with aristiform hairs on mid-dorsum of medium length (16-19 mm) and narrow (maximum width ¢.0-06 mm). Hindfeet are especially long compared with other congeners (mean length 44 mm). Skull is moderate in length and relatively narrow, more robust in parieto-occipital region where it is marked by ridges but becomes progressively more slender and delicate toward rostrum. Average skull length is 44-7 mm. Incisive foramina are an elongated oval, occupying c.45% of diastema; septum is complete with premaxillary part occupying ¢.75%; and vomeris not visible in ventral view. Post-orbital processes of zygoma are well developed and typically formed only by jugal. Yonenaga’s Spiny-rat is unique among its congeners in having laminar inflection ofjugal. Auditory bullae are large, smooth, and distinctly very inflated. Upper cheekteeth are the most simplified in the genus, with only single major fold and counterfold. Baculum is elongated (mean length 8-1 mm) and slender, with slight dorso-ventral curvature and slight lateral indentations near distal end but broadening proximally; distal end has median depression and apical wings, and proximal end is pointed. Karyotype is 2n = 54, FN = 104, with a large acrocentric X-chromosome and small metacentric Y-chromosome. Morphological and behavioral traits of Yonenaga’s Spiny-rat are very distinct relative to forest-dwelling congeners. These traits are broadly shared with other rodents inhabiting semiarid conditions elsewhere in the world and include medium-to-small body size, greatly inflated tympanic bullae, long hindfeet, long and strongly penciled tail, asymmetrical limb coordination, colonial behavior, and burrow-dwelling habits.
Habitat. Semiarid sandy dune habitat characterized by sparse vegetative cover in the Caatinga ecoregion. This is a very unique habitat for species of Trinomys. Local herbaceous vegetation is mainly spiny bromeliads and cacti, but the genus Eugenia (Myrtaceae) can comprise 35% of shrub and tree species.
Food and Feeding. Diet of Yonenaga’s Spiny-rat is almost exclusively seeds of Eugenia (Myrtaceae).
Breeding. There is no information available for this species.
Activity patterns. Captive Yonenaga’s Spiny-rats have regular circadian pattern of nocturnal activity.
Movements, Home range and Social organization. Yonenaga’s Spiny-rats live in self-dug burrow systems, with mean of9-9 occupied burrows per hectare. Each burrow system has 1-13 entrances. Adults of both sexes share a burrow system, and in some cases, the same nest within a burrow system. Perhaps unsurprisingly, therefore, intensity of interand intrasexualaffiliative behavior is high in laboratory experiments, with affiliation mediated by acoustic communication by both sexes and regardless of whether individuals belong to same or different social groups. Female Yonenaga’s Spiny-rats spend more time near familiar males than unfamiliar males—a pattern interpreted as social monogamy. Home ranges average 5-6 m? for males and 6-7 m? for females; those of the two sexes overlap extensively suggesting a promiscuous mating system. Patchy distribution of preferred food plants, coupled with propensity to cache food, might be important components in burrow sharing. Individuals might use secretions from anal scent glands as communication signals in social interactions. In captive studies, individuals use stop-and-go search strategy—a pattern of locomotion characterized by notable vigilance.
Status and Conservation. Classified as Endangered on The IUCN Red List. Yonenaga’s Spiny-rat has very limited distribution, highly restricted to sand dune habitat that faces continued threat from commercial sand extraction.
Bibliography. de Freitas, Carvalho et al. (2010), de Freitas, El-Hani & da Rocha (2008), Manaf & de Oliveira (2009), Manaf, de Brito-Gitirana & de Oliveira (2003), Manaf, Morato & de Oliveira (2003), da Rocha (1995), da Rocha et al. (2007), Santos & Lacey (2011).
description: Published as part of Don E. Wilson, Thomas E. Lacher, Jr & Russell A. Mittermeier, 2016, Echimyidae, pp. 552-604 in Handbook of the Mammals of the World – Volume 6 Lagomorphs and Rodents I, Barcelona :Lynx Edicions on page 562, DOI: 10.5281/zenodo.6623649