Otonyctomys hatti (Rodentia: Cricetidae) MAMMALIAN ... - BioOne

MAMMALIAN SPECIES 825:1–5 

Otonyctomys hatti (Rodentia: Cricetidae) 

M. CRISTINA MACSWINEY G., SILVIA HERNÁNDEZ-BETANCOURT, AND RAFAEL AVILA-FLORES 

School of Biological Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, United Kingdom; 

m.c.macswiney@abdn.ac.uk (MCMG) 

Facultad de Medicina Veterinaria y Zootecnia, Universidad Autónoma de Yucatán, Apartado Postal 4-116, Itzimná, Mérida, 

México (SH-B) 

Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada (RA-F) 

Abstract: Otonyctomys hatti Anthony, 1932, is a rodent commonly called the Yucatán vesper mouse. A medium-sized, 

brightly colored mouse, it is the only species in the genus Otonyctomys. It is endemic to the Yucatan Peninsula. It seems to 

have arboreal habits and occurs in semideciduous tropical forest and vegetation near water. It feeds on seeds, either on the 

ground or in shrubs, and soft-bodied fruits. It is considered a rare species throughout all of its geographic range but 

evaluation of its current conservation status is warranted. DOI: 10.1644/825.1. 

Key words: cricetid, endemic species, Mexico, rodent, Yucatán vesper mouse 

Published 26 February 2009 by the American Society of Mammalogists 

Synonymies completed 3 March 2008 www.mammalogy.org 

Otonyctomys Anthony, 1932 

Otonyctomys Anthony, 1932:1. Type species Otonyctomys 

hatti Anthony, 1932, by original designation. 

CONTEXT AND CONTENT. Order Rodentia, suborder Myomorpha, 

superfamily Muroidea, family Cricetidae, subfamily 

Tylomyinae. Otonyctomys is monotypic. 

Otonyctomys hatti Anthony, 1932 

Yucatán Vesper Mouse 

Otonyctomys hatti Anthony, 1932:1. Type locality ‘‘Chichen 

Itza, Yucatan, Mexico.’’ 

CONTEXT AND CONTENT. Context as above. Otonyctomys 

hatti is monotypic. 

NOMENCLATURAL NOTES. Otonyctomys hatti is called Yucatán 

vesper mouse in English, and Chó’ in Mayan (Navarro et 

al. 1990). Otonyctomys is from the Greek otos meaning ears, 

nyktos meaning night, and mys meaning mouse (Alvarez- 

Castañeda and Alvarez 1996). The specific epithet hatti is a 

patronym for Robert T. Hatt, who collected the 1st 

specimen (Anthony 1932). 

DIAGNOSIS 

Otonyctomys hatti (Fig. 1) is almost identical in external 

characters to the closely related Central American vesper 

mouse (Nyctomys sumichrasti), but its pelage is brighter 

russet (Anthony 1932). The most conspicuous character 

separating O. hatti from the genus Nyctomys is the size of 

auditory bulla, which is up to 3 times larger than that of N. 

sumichrasti (Anthony 1932). Overall, O. hatti is consistently 

smaller in most cranial measurements than N. sumichrasti, 

except breadth and depth of braincase, which are larger due 

to the effect of inflated bullae (Genoways et al. 2005). Cheek 

teeth and maxillary toothrow are noticeably smaller in O. 

hatti (Anthony 1932; Hall 1981); differences in toothrow size 

can be detected by direct observation without measurement 

(Genoways et al. 2005). External measurements are generally 

Fig. 1.—Adult Otonyctomys hatti, painted from life by Fiona A. 

Reid in Campeche, Mexico, 7 January 1989. Copyright Fiona 

A. Reid.

2 MAMMALIAN SPECIES 825—Otonyctomys hatti 

similar, but hind foot is narrower than in N. sumichrasti 

(Anthony 1932; Hall 1981). 

GENERAL CHARACTERS 

Otonyctomys hatti is a medium-sized, brightly colored 

mouse. Ears are of medium size, well covered with hair at the 

base but otherwise mostly naked (Anthony 1932). Pelage of 

upperparts is nearly uniform bright russet to hazel, with the 

darkest tone on the back; sides are tawny to ochraceous 

tawny; individual hairs of upperparts are blackish slate at 

base and lighter apically; pelage of venter is white or creamy 

from base to tip of hairs; dark facial spots present anterior to 

eyes and at the base of whiskers; upper side of feet whitish 

washed with buff or tawny tones (Anthony 1932; Hall 1981; 

Peterson 1966). The tail is well furred with individual hairs 

that increase in length from base to tip of tail; pelage of tail 

is bone-brown both above and below (Anthony 1932). There 

are 2 pairs of inguinal mammae (Anthony 1932). 

No sexual dimorphism is apparent from available 

specimens. External measurements (means, ranges in parentheses, 

in mm or g) of 9–14 adult individuals of both sexes 

were: total length, 201.9 (163–231); length of body and head, 

100.6 (90–116); length of tail, 102.6 (60–127); length of hind 

foot, 21.3 (18–23); length of ear, 15.0 (13–20); and body 

mass, 29.0 (23–36—Anthony 1932; Aranda et al. 1997; 

Genoways et al. 2005; Hernández-Huerta et al. 2000; Jones 

et al. 1974; Peterson 1966; Rick 1965; Vargas-Contreras et 

al. 2004). External measurements (in mm or g) of 3 juveniles 

from Guatemala and Quintana Roo were: total length, 157, 

130, 160; length of body and head, 72, 65, 75; length of tail, 

85, 65, 85; length of hind foot, 20, 18, 10; length of ear, 11, 

10, 14; and body mass, 13, 5.5, 10 (Aranda et al. 1997; 

Peterson 1966; Rick 1965). 

Rostrum is relatively short; auditory bullae are disproportionally 

large and occupy most of the basicranial 

region (Fig. 2); zygomatic arch is compressed rather than 

flaring; anterior margin of zygomatic plate approximately 

perpendicular to palatal plane; mandible is delicate with a 

low coronoid process and a weak ascending ramus; cheek 

teeth are noticeably small (Anthony 1932; Hall 1981). Skull 

measurements (means, ranges in parentheses, in mm) of 3–9 

adult specimens were: greatest length of skull, 28.3 (26.8– 

29.5); condylobasal length, 26.5 (24.4–28.5); length of nasals, 

9.0 (8.4–9.3); zygomatic breadth, 15.1 (14.4–16.2); least 

interorbital breadth, 5.2 (5.0–5.5); breadth of braincase, 13.7 

(13.1–14.3); depth of braincase, 11.7 (11.5–12.0); length of 

rostrum, 9.3 (8.8–9.8); breadth of rostrum, 5.0 (4.8–5.2); 

mastoid breadth, 13.7 (13.0–14.5); length of palatal bridge, 

4.3 (3.9–4.6); length of upper toothrow, 4.2 (3.8–4.4); length 

of lower toothrow, 4.2 (4.0–4.4); length of incisive foramen, 

4.6 (4.4–5.1); length of auditory bulla, 8.5 (8.0–9.5); and 

breadth of auditory bulla, 6.9 (6.6–7.9—Anthony 1932; 

Aranda et al. 1997; Genoways et al. 2005; Hernández- 

Fig. 2.—Dorsal, ventral, and lateral views of cranium and lateral 

view of mandible of a subadult female Otonyctomys hatti 

(IBUNAM [Instituto de Biología, Universidad Nacional Autónoma 

de México] 30792, formerly ROM 95785). Greatest length of 

skull is 26.2 mm. Photograph by R. List. 

Huerta et al. 2000; Jones et al. 1974; Peterson 1966; Rick 

1965). 

DISTRIBUTION 

Otonyctomys hatti is endemic to the Yucatan Peninsula 

(Fig. 3). The range of O. hatti includes northeastern 

Guatemala, central and northern Belize, and most of the

825—Otonyctomys hatti MAMMALIAN SPECIES 3 

Fig. 3.—Geographic distribution of Otonyctomys hatti in the 

Yucatan Peninsula. Localities for Recent specimens are indicated 

by solid circles (N ) and fossil material is indicated by solid triangles 

(m). Modified from Genoways et al. 2005. 

Mexican states of Campeche, Yucatan, and Quintana Roo 

(Genoways et al. 2005; Hall 1981). O. hatti mouse has been 

recorded at only 10 localities: Chichén-Itzá, Yucatan; 

Calakmul, Conhuás, Escárcega region, and Dzibalchén, 

Campeche; Rancho Las Palmas and Reserva Ecológica El 

Edén, Quintana Roo; Cayo District and Rockstone Pond, 

Belize; and Tikal, Guatemala (Anthony 1932; Aranda et al. 

1997; Genoways et al. 2005; Hernández-Huerta et al. 2000; 

Jones et al. 1974; Laurie 1953; Peterson 1966; Rick 1965; 

Vargas-Contreras et al. 2004). Elevational range of known 

localities is sea level to 250 m. 

FOSSIL RECORD 

Remains of Otonyctomys hatti are from Pleistocene 

deposits in caves Lara, Has, Loltún, Coyok, Chacaljas, and 

Spukil in Yucatan, Mexico. The largest number of remains 

correspond to cave Spukil, where 18 mandibles, 2 upper 

toothrows, and other fragments were recovered (Hatt et al. 

1953). 

FORM AND FUNCTION 

Pelage of juvenile individuals is duller in color and lacks 

the glossiness of the adults (Rick 1965). The skull of 

Otonyctomys hatti is characterized by the greatly inflated 

auditory bullae (Genoways et al. 2005; Peterson 1966). 

Dental formula is i 1/1, c 0/0, p 0/0, m 3/3, total 16. 

ONTOGENY AND REPRODUCTION 

Individuals of Otonyctomys hatti may be separated into 

3 age classes (juvenile, subadult, and adult) based on tooth 

wear, cranial measurements, and body measurements. 

Breeding may occur in 2 peaks during summer and winter. 

At Chichén-Itzá, females with enlarged uteri were captured 

in October and July (Hatt 1938; Jones et al. 1974); a 

lactating female was present in February in Quintana Roo 

(Aranda et al. 1997). 

ECOLOGY AND BEHAVIOR 

Otonyctomys hatti occurs in mature semideciduous 

tropical forests that are relatively open (Aranda et al. 

1997; Genoways et al. 2005; Hernández-Huerta et al. 2000; 

Vargas-Contreras et al. 2004), and vegetation near cenotes 

(water-filled sinkholes—Jones et al. 1974). In Belize, vesper 

mice were restricted to the broad-leafed forests of the 

northern plains and watersheds of rivers (McCarthy 1998). 

Otonyctomys hatti seems to have strongly arboreal 

habits. It has been trapped on dead logs (Genoways et al. 

2005), in trees (Hernández-Huerta et al. 2000; Jones et al. 

1974), on lianas (Peterson 1966), and from the top of a 

coconut palm (Peterson 1966), usually at 1–2 m from the 

ground. In Reserva de la Biofera Ria Lagartos, Yucatan, 1 

individual was observed in June 2005 using an abandoned 

nest of a woodpecker in a dead tree at 1.8 m from the 

ground (J. Chablé, pers. comm.). 

Otonyctomys hatti also is found in human-made 

structures. Two individuals were trapped between the thatch 

and wall of a guest house at Chichén-Itzá (Anthony 1932); 1 

was taken on a rafter under the roof of a house in Campeche 

(Jones et al. 1974); and 1 in the main station building La 

Sabana of Reserva Ecológica El Edén, Quintana Roo 

(Aranda et al. 1997). The individuals from Tikal were 

probably collected from the thatched wooden houses in the 

camp (Rick 1965). In June 2002, 2 individuals were observed 

on a rafter under the roof of a house at cenote Lucero 

(16 km road Cancun–Puerto Morelos, Quintana Roo—J. 

Chablé, pers. comm.). 

Otonyctomys hatti feeds on seeds on the ground or in 

shrubs (McCarthy 1993) and probably also on soft-bodied 

fruits (Genoways et al. 2005). O. hatti has been caught in the 

same trap lines with other species of rodents including 

Heteromys gaumeri, Oryzomys melanotis, Ototylomys phyllotis, 

and Peromyscus yucatanicus (Genoways et al. 2005; Hatt 

1938). Competition between O. hatti and N. sumichrasti might 

occur in a small area of Belize considering the similar size of 

these 2 highly arboreal mice and their reliance upon fruit in

4 MAMMALIAN SPECIES 825—Otonyctomys hatti 

Fig. 4.—Karyotype of a female Otonyctomys hatti collected in 

Campeche, Mexico (from Genoways et al. 2005; republished with 

permission of the authors). 

their diet. This may explain the lack of geographic overlap in 

most of their distributional ranges (Genoways et al. 2005). 

Bone remains of O. hatti have been found in owl pellets 

(Hatt et al. 1953). The ectoparasitic chigger Eutrombicula 

alfreddugesi (Acarina, Trombiculidae) was found on a 

female O. hatti taken at Chichén-Itzá (Loomis 1969). 

Otonyctomys hatti is usually trapped in Sherman live 

traps with banana as bait (Genoways et al. 2005; Hernández- 

Huerta et al. 2000; Jones et al. 1974; Peterson 1966). A 

female was accidentally captured in a mist net set in 

Campeche, Mexico (Vargas-Contreras et al. 2004). An adult 

male was held in captivity for nearly 2 months (Genoways et 

al. 2005). In captivity, O. hatti is nocturnal, extremely shy, 

and prefers seeds to fruit (Reid 1997). 

GENETICS 

The diploid number (2n) for Otonyctomys hatti is 50 and 

fundamental number (FN) is 62 (Genoways et al. 2005; Fig. 4). 

The karyotype comprises 7 pairs of large to small metacentric 

to submetacentric chromosomes and a graded series of 17 pairs 

of large to small acrocentric elements. The X is metacentric and 

is the largest chromosome in the complement. The Y is large 

and submetacentric (Genoways et al. 2005). 

CONSERVATION 

Otonyctomys hatti is considered a rare species throughout 

all of its geographic range (Genoways et al. 2005). There 

are only 18 specimens known to date. The Mexican list of 

endangered species (NOM-059-ECOL-2001) considers O. 

hatti as a threatened species (Secretaría de Medio Ambiente 

y Recursos Naturales 2002). Although this species might not 

be under risk of extinction, evaluation of its current 

conservation status is warranted (Juárez 2005). 

ACKNOWLEDGMENTS 

We especially thank F. A. Reid for providing the 

illustration in Fig. 1; the Colección Nacional de Mamíferos 

(CNMA), Instituto de Biología, Universidad Nacional 

Autónoma de México, for loaning us the specimen 

illustrated in Fig. 2; and R. M. Timm for critically 

evaluating an earlier draft of the manuscript. 

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Otonyctomys hatti (Rodentia: Muridae) en Quintana Roo, 

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825—Otonyctomys hatti MAMMALIAN SPECIES 5 

SECRETARÍA DEMEDIO AMBIENTE Y RECURSOS NATURALES. 2002. Norma 

Oficial Mexicana NOM-059-ECOL-2001. Protección ambiental— 

especies nativas de México de flora y fauna silvestres—categoría 

de riesgo y especificaciones para su inclusión, exclusión o 

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Mexico City, Distrito Federal, Mexico. 

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Associate editors of this account were PAMELA OWEN and ERIC RICKART. 

Editor was MEREDITH HAMILTON.

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