755.

Sumichrast’s Vesper Rat

Nyctomys sumichrasti

French: Nyctomys de Sumichrast / German: Sumichrast-Vesperratte / Spanish: Rata laucha de Sumichrast

Other common names: Vesper Rat

Taxonomy. Hesperomys sumichrasti Saussure, 1860, Cordillera in the provincia of Vera-Cruz, Mexico. Restricted by T. Alvarez in 1963 to Uvéro, 20 km north-west of Santiago Tuxtla, Veracruz, Mexico.

Recent phylogenetic studies have shown that Nyctomys is paraphyletic. Upland populations are genetically and morphometrically distinct from lowland populations. Nevertheless, the genusis currently under taxonomic revision. Nine subspecies recognized.

Subspecies and Distribution.

N.s.sumichrastiSaussure,1860—SEMexico(SVeracruz,WTabasco,andextremeNOaxaca).

N.s.colimensisLaurie,1953—SWMexico(SJalisco,Colima,SMichoacan,andSGuerrero).

N.s.costaricensisGoldman,1937—WCostaRica.

N.s.decolorusTrue,1894—extremeEGuatemala,SBelize,andNWHonduras.

N.s.florenceiGoldman,1937—extremeSEGuatemala,ElSalvador,SHonduras,andNWNicaragua.

N.s.natellinusBangs,1902—ECostaRicaandPanama.

N.s.pallidulusGoldman,1937—SEMexico(SOaxacaandWChiapas).

N.s.salviniTomes,1862—SEMexico(EChiapas)andC&SGuatemala.

N. s. venustulus Goldman, 1916 — S & SE Nicaragua and NE Costa Rica.

Descriptive notes. Head—body 128-140 mm, tail 143-155 mm; weight 40-55 g. Sumichrast’s Vesper Rats have large heads, long whiskers, and small ears, longer than wide and almost naked. Eyes are relatively large, with mask of dark brown to black hairs. Fur is soft and thick, dorsum varies from tawny to orange, sides are same color as back but lighter, and venter varies from white to cream. Legs are white. Hindlegs are short and broad; except for the first, fingers are long and fourth finger is the longest; six pads are very developed; and plantar surface is naked and has compressed curved claws, modified for arboreal life. Tail is longer than body, brown, and hairy; it terminates in tuft resembling brush. There are two pairs of nipples. Size and shape of skull are not sexually dimorphic. Chromosomal complement has FN = 50-52, 2n = 22 pairs of acrocentric chromosomes, and long subtelocentric couple in the X-chromosome. Subspecies vary by geography and color.

Habitat. High forests, tropical forest, lowland forest, riparian vegetation, deciduous forests, tropical dry forest associated with fields of sugar cane, cloud forest with agricultural disturbance, secondary vegetation, along streams, forests associated with water bodies and weeds associated with coconut trees from sea level up to elevations of 2950 m.

Food and Feeding. Sumichrast’s Vesper Rat feeds mainly on fruits, flowers, seeds, and insects. It has been reported to eat fruits, Psychotria gracilis and Hoffmania sp. (both Rubiaceae), and insects such as moths. In Jalisco, Mexico, it eats fruits ofJacquinia pungens ( Primulaceae). In Nicaragua, it eats fruits of Cordia diversifolia ( Boraginaceae) in the wet season and fruits of Ficus sp. (Moraceae) in the dry season. It is considered a pest of cacaotrees ( Theobroma cacao, Malvaceae). In Costa Rica,it eats young leaves of Daphnopsis americana (Thymelaeaceae) . Sumichrast’s Vesper Rats have been caught in traps baited with a blend of vanilla, oatmeal, and peanut butter, and in Nicaragua,in traps baited with tomato. In captivity, they are fed a diet ofseeds and fruits from Spondias purpurea ( Anacardiaceae), Crescentia alata ( Bignoniaceae), and Terminalia catappa ( Combretaceae).

Breeding. Sumichrast’s Vesper Rats breed year-round in wet and dry seasons. In Panama, females are pregnant in February—June, and lactation first occurs in March. Males have enlarged testicles in December—June. In Colima, Mexico, lactating females can be found in January. Sumichrast’s Vesper Rats make nests in forks of trees using vegetable fibers and leaves. In the region of Monteverde, Costa Rica, nests are often found at entrances of human houses surrounded by vegetation and made of remnants of paper, foam mattresses, and clothes. In captivity, copulation occurs after self-grooming; male mounts female for 30-40 seconds. A female, on average, has five litters in seven months, and gestation lasts 30-38 days. Litters have 1-4 young that attach to teats of their mothers for c.2 weeks. In captivity, both adults build globular nests where births occur; a male usually leaves the nest seven days after birth. Young are born with hair on dorsum and bare bellies; their total lengths are ¢.77 mm (tail 22 mm), and they weigh 4-5 g. At two days old, they can perform weak and slow movements, but they are slow on inclines. At 15 days old when their eyes open, movements become deliberate, and motor coordination is similar to adults. They leave nests after 17 days. Sexual maturity can be reached at 75 days old. Sumichrast’s Vesper Rats can be separated intofive age categories based on appearance, pelage characteristics, wear ofteeth, and cranial (e.g. sutures) and somatic metrics.

Activity patterns. Sumichrast’s Vesper Ratis arboreal and most active at night. In Costa Rica, it commonly inhabits the canopy, and it is rarely observed because ofits arboreal and nocturnal habits. In Colima, Mexico, only 29 individuals were captured in five years during 40,000 trap-nights. In Jalisco, Mexico, Sumichrast’s Vesper Rats are active on the ground and in tree tops. In captivity, they are nocturnal, although individuals leave nests to drink or urinate during the day; they leave nests two hours after dark to feed.

Movements, Home range and Social organization. Sumichrast’s Vesper Rats are agile in trees and usually found ¢.3 m up in tree canopies. On the ground, they move in areas with dense vegetation and trees. In Jalisco, Mexico, individuals move more during the dry season in search of food and less during rain after shelters are located. Males travel longer distances than females, in Oaxaca males travel in average 35-4 m and females 34-9 m. In captivity, they deliberately move somewhat erratically when feeding, handling food, and grooming. A Sumichrast’s Vesper Rat can perch on branches like a bird; it hangs its tail vertically at 30-45° angles, while its front legs and head rest on its chest—a very strong, balanced posture. Vocalizations consist of squeaks at frequencies of 3-5 kHz, repeated at irregular intervals and used to locate mates, when excited, and while young play. To locate mates in a nest, males vocalize in low tones at intervals of ¢.5 minutes. Sumichrast’s Vesper Rats live in family groups and become aggressive when introduced to strangers. They live for c.5 years in captivity.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Sumichrast’s Vesper Rat has a wide distribution, is tolerant of habitat modification, and occurs in protected areas. Nevertheless, there is a lack of information because of their arboreal habits.

Bibliography. Alvarez (1963b), Alvarez-Castafieda et al. (2015), Birkenholz & Wirtz (1965), Chavarria (2013), Corley et al. (2011), Dominguez-Castellanos et al. (2007), Genoways & Jones (1972), Goldman (1916), Hunt et al. (2004), Lira & Vargas (2009), Pena et al. (2006), Pérez-Lustre & Santos-Moreno (2010), Ramirez-Pulido, Gonzalez-Ruiz et al. (2014), Reid (2009), Romero & Timm (2013), Schnell, Abreu et al. (2010), Timm & Vriesendorp (2003), Vazquez (2016), Wilson & Cole (2000).