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UNIVERSITY OF KANSAS PUBLICATIONS
MUSEUM OF NATURAL HISTORY

Volume 9, No. 19, pp. 519-529
January 14, 1960


Records of Harvest Mice, Reithrodontomys,
from Central America, with Description
of a New Subspecies from Nicaragua

BY

SYDNEY ANDERSON AND J. KNOX JONES, JR.


UNIVERSITY OF KANSAS
LAWRENCE
1960




UNIVERSITY OF KANSAS PUBLICATIONS, MUSEUM OF NATURAL HISTORY

Editors: E. Raymond Hall, Chairman, Henry S. Fitch,
Robert W. Wilson

Volume 9, No. 19, pp. 519-529
Published January 14, 1960


UNIVERSITY OF KANSAS
Lawrence, Kansas


PRINTED IN
THE STATE PRINTING PLANT
TOPEKA, KANSAS
1960

28-1279




Records of Harvest Mice, Reithrodontomys,
from Central America, with Description
of a New Subspecies from Nicaragua

BY

SYDNEY ANDERSON AND J. KNOX JONES, JR.


Since 1952 when Hooper's review of Latin American harvest mice was
published, collectors from the Museum of Natural History of the
University of Kansas have visited several countries in Central America,
and have obtained many additional specimens. Among these we find a new
subspecies of _Reithrodontomys fulvescens_ from Nicaragua, significant
extensions of known geographic range for several other species, and
additional information on variation in some little known kinds.
Specimens in the Museum of Natural History of _Reithrodontomys
mexicanus cherriei_, _Reithrodontomys tenuirostris_, and
_Reithrodontomys creper_ that are from within the geographic and
altitudinal ranges listed by Hooper (1952) are not included in this
report.

     All place names are on the map of Hispanic America published
     by the American Geographical Society and can be located by
     consulting the "Index to map of Hispanic America" (Vol. 1,
     Geographical names in Central America, U. S. Government
     Printing Office, Washington, D. C., 1943.) All measurements
     cited are in millimeters.

     Support for field work was provided by the Kansas University
     Endowment Association. Support for the laboratory phases of
     the work came in part from a grant from the National Science
     Foundation. Most of the specimens herein reported were
     collected by James W. Bee in late 1954 and early 1955, and
     by J. R. Alcorn and A. A. Alcorn in 1955 and 1956. A few
     that were collected earlier by other persons are mentioned.
     We are indebted to the following individuals for the loan of
     specimens in their care: R. G. Van Gelder, American Museum
     of Natural History; Philip Hershkovitz, Chicago Natural
     History Museum; W. H. Burt and E. T. Hooper, Museum of
     Zoology, University of Michigan; and D. H. Johnson and C. O.
     Handley, Jr., U. S. National Museum.

~_Reithrodontomys sumichrasti australis_~ J. A. Allen.--Seven specimens
from the vicinity of Volcan Irazú, Cartago, Costa Rica, are from within
the geographic and altitudinal range recorded for the subspecies by
Hooper (1952:82).

One female, KU 26967, trapped on March 2, 1947, on the SW slope of
Volcan Irazú, 8500 ft., contained five embryos that were 17 mm. in
crown-rump length.

~_Reithrodontomys sumichrasti dorsalis_~ Merriam.--A total of 93
females are among 195 specimens from 24 localities in Guatemala that
lie within the geographic and altitudinal range recorded by Hooper
(1952:78) for _dorsalis_.

Two females were pregnant; KU 71363, taken on January 28, 1956, 7 mi.
E, 2 mi. S La Unión, Quetzaltenango, Guatemala, contained three embryos
that were 7 mm. in crown-rump length, and KU 65245, taken on December
15, 1954, 1 mi. NE Nebaj, 6000 ft., El Quiche, Guatemala, contained
four embryos that were 15 mm. in crown-rump length. These two females
were the only pregnant ones among 36 taken in December, 23 in January,
1 in February, 19 in March, 5 in April, and 9 in August.

~_Reithrodontomys fulvescens chiapensis_~ Howell.--GUATEMALA.--Baja
Verapaz: 1/2 mi. N, 1 mi. E Salamá, 3200 ft., 1 (KU 65378--January 28,
1955); 1 mi. S Rabinal, 3450 ft., 4 (KU 65379-82--January 29, 1955); 5
mi. N, 1 mi. W [Santa Cruz] El Chol, 6000 ft., 1 (KU 65375--January 30,
1955). Guatemala: 5 mi. S Guatemala City, 4950 ft., 2 (KU
65371-72--March 13, 1955); 7 mi. S, 6 mi. E Guatemala City, 5800 ft., 1
(KU 65370--March 14, 1955). Santa Rosa: 2 mi. N, 2 mi. W Cuilapa [=
Cuajiniquilapa], 2980 ft, 2 (KU 65376-77--March 5, 1955).

The specimens from the departments of Guatemala and Santa Rosa are from
localities that lie on the Pacific slope and are southwest of the
previously known range of the species (see Hooper, 1952:93). The
specimens from 1/2 mi. N and 1 mi. E Salamá and from 1 mi. S Rabinal
are paler dorsally than other Guatemalan specimens available to us,
including the specimen from the nearby locality, 5 mi. N and 1 mi. W El
Chol.

Specimens from Nicaragua that are recognizable by the E-shaped pattern
of the worn occlusal surface of the third upper molars and by the
S-shaped occlusal pattern of the third lower molars as of the species
_Reithrodontomys fulvescens_, extend the known range of the species
approximately 200 kilometers southeast from the vicinity of
Tegucigalpa, Honduras (Hooper, 1952:93). The Nicaraguan specimens are
described below as a new subspecies.


~Reithrodontomys fulvescens meridionalis~, new subspecies

     _Type specimen._--Skin and skull of adult male, no. 71388
     Museum of Natural History, University of Kansas, from 9 mi.
     NNW Estelí, Estelí, Nicaragua; obtained by J. R. Alcorn on
     July 15, 1956; original number 21,464.

     _Diagnostic characters._--A short-tailed _Reithrodontomys
     fulvescens_ having a distinctly streaked or "peppered," and
     short pelage composed of relatively dark hairs as well as
     relatively brightly colored hairs on dorsum and
     white-tipped hairs on venter; and having shallow skull,
     elongate and posteriorly attenuate incisive foramina, small
     postpalatal foramina, broad interorbital region, and
     mid-dorsal depression at junction of nasal and frontal
     bones.

_Comparisons._--Each of three adults of _meridionalis_ (trapped in
February and March) can be distinguished from seven adults of the
geographically adjacent _R. f. chiapensis_ from Guatemala (trapped in
late January and in March) by shorter tail, more streaked or "peppered"
dorsal pelage, yellower hue of non-blackish parts of hairs on dorsum,
less distinct mid-dorsal darkening, and more whitish (less buffy)
venter.

Four specimens of _meridionalis_ trapped in July at the type locality,
only one mile from the locality of capture of the February-taken
specimens, are distinctly darker dorsally and slightly darker ventrally
than the three _meridionalis_ trapped in February and March, but
resemble the latter three in shortness of tail and in having short,
"peppered" dorsal pelage. We lack specimens of _chiapensis_ in summer
pelage. According to Hooper (1952:122) the summer pelages of _R. f.
chiapensis_ and _R. f. helvolus_ are indistinguishable. Our
_meridionalis_ differ from five summer-taken specimens of _helvolus_ in
shorter, more "peppered," and distinctly darker dorsal pelage.

Six skulls of _meridionalis_ were matched with six skulls of
_chiapensis_ having approximately the same amount of wear on the teeth,
and the series were compared, pair by pair, in various cranial
characters. In five of the six pairs _meridionalis_ had a less inflated
braincase, and smaller postpalatal foramina, and in each of the six
pairs _meridionalis_ had a greater depression in the frontonasal region
and posteriorly more acute incisive foramina. Four external
measurements and nine cranial measurements were compared using the
series of _meridionalis_, the series of _chiapensis_ from Guatemala,
and Hooper's (1952:213) measurements of seven _chiapensis_ from central
Chiapas. The lesser average and maximum total length of skull in
_meridionalis_ than in either series of _chiapensis_ suggests that
_meridionalis_ has a smaller skull. Externally, the lesser total length
of _meridionalis_ is largely owing to its shorter tail; there is little
difference in length of head and body between _meridionalis_ and
_chiapensis_. The longest tail among our _meridionalis_ is shorter than
the shortest tail among the _chiapensis_ (disregarding two Guatemalan
specimens of _chiapensis_ that probably had injured tails). The
interorbital breadth of _meridionalis_ is on the average greater and
the depth of cranium is less than in _chiapensis_. There is some
overlap in the range of each of these two cranial measurements, but in
all _meridionalis_ the interorbital breadth exceeds 42 per cent of the
depth of cranium, and in all _chiapensis_ is less than 42 per cent. The
length of the incisive foramina in _meridionalis_, expressed as a
percentage of the total length of the skull, is usually greater than in
_chiapensis_.

One of our specimens (KU 71389) contained four embryos that measured 5
mm. in crown-rump length.

     _Measurements._--Selected measurements of the holotype,
     followed by the average and extreme measurements of six
     specimens of _meridionalis_ (including the holotype) from
     the vicinity of the type locality are: total length, 154,
     152.0 (148-154); length of tail, 82, 82.0 (81-83); length of
     hind foot, 17, 18.0 (17-19); length of ear from notch, 13,
     13.3 (12-14); total length of skull, 21.4, 21.13
     (20.3-21.7); zygomatic breadth, 10.0, 10.38 (10.0-10.6);
     breadth of braincase, 10.1, 10.17 (9.9-10.4); depth of
     skull, 8.2, 8.00 (7.8-8.3); interorbital constriction, 3.7,
     3.53 (3.4-3.7); breadth of rostrum, 3.8, 3.75 (3.6-3.9);
     length of rostrum, 7.4, 7.33 (7.1-7.7); length of incisive
     foramen, 4.6, 4.47 (4.2-4.6); length of upper molar
     tooth-row, 3.2, 3.32 (3.2-3.5). Corresponding measurements
     of a specimen from 11 mi. SE Darío are: 153, 82, 18, 13,
     20.7, 10.3, 10.1, 7.8, 3.4, 3.6, 7.2, 4.3, and 3.2.

     _Specimens examined, 8, as follows_: NICARAGUA.--Estelí: 9
     mi. NNW Estelí, 4 (KU 71386-89--July 15, 1956); 8 mi. NNW
     Estelí, 3 (KU 71393-95--February 5, 1956). Matagalpa: 11 mi.
     SE Darío, 1 (KU 71392--March 21, 1956).

     Specimens of _Reithrodontomys fulvescens helvolus_ used in
     comparisons: OAXACA: 3 mi. ESE Oaxaca, 1 (KU 68891--June 24,
     1955); 3 mi. W Mitla, 4 (KU 68892-95--August 5 to 9, 1955).

~_Reithrodontomys gracilis anthonyi_~ Goodwin.--EL SALVADOR.--Santa
Ana: 2 mi. SE San Cristóbal, 2950 ft., 2 (KU 65401-02--March 6, 1955).
GUATEMALA.--Jutiapa: 2-1/2 mi. W, 2-1/4 mi. N San Cristóbal [El
Salvador], 2900 ft., 5 (KU 65396-400--March 6, 1955).

The subspecies _anthonyi_ has been known previously by seven specimens,
none of which is fully adult, judging from Hooper's (1952:134) comment
that the adult pelage of _anthonyi_ is unknown. Six of our seven
specimens are clearly adults as is shown by well-worn teeth and degree
of development of temporal ridges. The seventh is a young animal in
process of postjuvenal molt. Individuals from our series in general
resemble specimens of _Reithrodontomys mexicanus orinus_ from the
vicinity of Guatemala City but differ from the latter as follows:
dorsal pelage brighter (with less suffusion of black), "peppered" in
appearance, shorter and sparser; ears distinctly paler, owing both to
the paler color of the skin and the paleness of the hairs inside the
pinna; dark tarsal stripe not extending onto hind foot; ears and hind
feet uniformly smaller; averaging smaller in cranial dimensions (but
there is considerable overlap), braincase less convex dorsally.

Measurements of the adult _anthonyi_ now available show that the
subspecies reaches a greater size than was apparent in the sample
available to Hooper. Consequently the three largest adults would be
identified as _R. mexicanus_ according to Hooper's key (1952:31),
rather than _R. gracilis_, and the three smallest adults could not be
unequivocably identified as either one species or the other.

The ranges of _R. gracilis_ and _R. mexicanus_ are allopatric except in
southern Guatemala where the ranges overlap. However, the two species
have not been taken there at the same place.

In comparison with May-taken adults of _R. g. harrisi_ from 3 mi. SW
Managua, Nicaragua, the adult _anthonyi_ average brighter (more orange)
in color (but two of the _anthonyi_ cannot be distinguished by color
when placed with the _harrisi_), and are larger in total length, length
of tail, and size of skull.

One female (KU 65400) contained two embryos that measured 18 mm. in
crown-rump length.

     Average and extreme external and cranial measurements of the
     six adults are: total length, 183.6 (170-198); length of
     tail, 106.0 (95-113); length of hind foot, 18.0 (18); length
     of ear from notch, 14.0 (14); total length of skull, 22.21
     (21.4-22.8); zygomatic breadth, 11.20 (10.9-11.7); breadth
     of braincase, 10.90 (10.3-11.4); depth of skull, 8.36
     (8.0-9.0); length of rostrum, 7.60 (7.3-7.8); breadth of
     rostrum, 4.24 (4.0-4.6); interorbital constriction, 3.78
     (3.6-4.0); length of incisive foramen, 4.05 (3.8-4.3);
     length of upper molar tooth-row, 3.28 (3.1-3.4). Weight in
     grams of the adults averaged 14.3 (12-17).

~_Reithrodontomys gracilis gracilis_~ Allen and
Chapman.--GUATEMALA.--El Petén: Uaxactún, 1500 ft., 2 (KU
65384-85--April 3, 1955).

These specimens are the first of the subspecies to be recorded from
Guatemala. Uaxactún is near, but not within, the range of _R. g.
gracilis_ as mapped by Hooper (1952:131). The male, KU 65384, and
female, KU 65385, are adults with comparatively unworn molar teeth.
Respective external measurements are: total length, 178, 175; length of
tail, 106, 102; length of hind foot, 18.5, 19; length of ear from
notch, 14, 14.

~_Reithrodontomys gracilis harrisi_~ Goodwin.--NICARAGUA.--Estelí: 9
mi. NNW Estelí, 1 (KU 71342--July 15, 1956). Managua: 3 mi. SW Managua,
15 (KU 71345-59--February, May, June, 1956); 4 mi. W Managua, 2 (KU
71360-61--June 26, 28, 1956).

Comments on the series from 3 mi. SW Managua have appeared elsewhere
(Englert, 1959:153). The specimen from 9 mi. NNW Estelí contained four
embryos that measured 5 mm. in crown-rump length.

~_Reithrodontomys gracilis pacificus_~ Goodwin.--EL SALVADOR.--San
Salvador: 1 mi. NW San Salvador, 1 (KU 71396--July 29, 1956).

In coloration (being but slightly paler), and in small size, this
specimen resembles the description of _R. g. pacificus_ given by Hooper
(1952:135) and ten specimens of _pacificus_ (nine from Guatemala and
one from Chiapas) examined by us. Because of this resemblance and the
marked contrast with specimens of _R. g. anthonyi_ discussed above we
assign this specimen to _pacificus_. In comparison with two topotypes
(AMNH 79062, 79090) of _R. g. anthonyi_ from Sacapulas, Guatemala,
taken on February 9 and March 2 that are essentially the same age as KU
71396, the latter specimen is darker dorsally, the tail is darker both
dorsally and ventrally, and the skull is smaller. In paleness of upper
surface of hind feet, length of palate relative to length of incisive
foramina, and size of bullae, KU 71396 resembles _anthonyi_. We
interpret these resemblances to _anthonyi_ as evidence of
intergradation between _pacificus_ and _anthonyi_. Felten (1958:9)
referred two specimens from El Salvador (one from San Salvador and one
from Amate de Campo, Departmento de La Paz) to _anthonyi_, without
comparison with _pacificus_ and with no mention of examination of other
specimens of _Reithrodontomys gracilis_. When the distribution and
variation of _R. gracilis_ in this region are more adequately known
these two specimens may well be reassigned to _pacificus_. Hooper
(1952:134) observed that two specimens from Monte Cristo Mine in
eastern El Salvador were the smallest and darkest of the _R. g.
anthonyi_ examined by him and approached _R. g. pacificus_ in these
particulars. Possibly these specimens from Monte Cristo Mine also
should be assigned to _pacificus_ rather than _anthonyi_. External
measurements of KU 71396 are: total length, 167; length of tail, 99;
length of hind foot, 19; length of ear from notch, 13. The specimen
contained four embryos that measured 10 mm. in crown-rump length.

~_Reithrodontomys microdon microdon_~
Merriam.--GUATEMALA.--Huehuetenango: 2 mi. S San Juan Ixcoy, 9340 ft.,
10 (KU 65404-13--December 24 and 25, 1954); 3-1/2 mi. SW San Juan
Ixcoy, 10,120 ft., 4 (KU 65210, 65414-15, 65417--December 27 and 28,
1954). San Marcos: 3-1/4 mi. N, 3/4 mi. E San Marcos, 9500 ft, 1 (KU
65420--March 22, 1955). Totonicapán: 5 mi. ESE Totonicapán, 4 (KU
68897-900--July 17, 1955).

All the localities from which we have examined specimens fall within
the geographic range of the subspecies as mapped by Hooper (1952:168).
He examined six specimens of _R. m. microdon_ and listed external and
cranial measurements for only two specimens.

     Average and extreme external measurements of 13 adults (7
     males, 6 females) from the vicinity of San Juan Ixcoy are:
     total length, 176.5 (168-187); length of tail, 105.8
     (100-110); length of hind foot, 19.5 (19-20); length of ear
     from notch, 16.8 (15-18). The average weight in grams of
     these same specimens is 9.1 (8-11). Average and extreme
     cranial measurements of 12 specimens from the same series (7
     males, 5 females) are: total length of skull, 22.55
     (21.6-23.0); zygomatic breadth, 10.82 (10.2-11.2); breadth
     of braincase, 11.02 (10.6-11.4); depth of skull, 8.67
     (8.4-8.9); interorbital constriction, 3.78 (3.6-3.9);
     breadth of rostrum, 3.86 (3.6-4.0); length of rostrum, 8.33
     (8.1-8.6); length of incisive foramen, 4.27 (4.0-4.5);
     length of palate, 3.48 (3.2-3.8); length of upper molar
     tooth-row, 3.25 (3.0-3.4).

~_Reithrodontomys mexicanus howelli_~ Goodwin.--GUATEMALA.--Baja
Verapaz: 5 mi. N, 1 mi. W [Santa Cruz] El Chol, 6000 ft., 3 (KU 65315,
65386-87--January 30, 1955). El Quiche: 1 mi. NE Nebaj, 6000 ft., 2 (KU
65275, 65277--December 19, 1954). Huehuetenango: 5 mi. E, 1 mi. N
Huehuetenango, 7000 ft., 2 (KU 65418-19--December 22, 1954). Santa
Rosa: 1 mi. WSW El Molino [= approximately 1 mi. S, 6 mi. E
Cuajiniquilapa], 1 (KU 71315--August 3, 1956).

The specimen from 1 mi. WSW El Molino is from within the range of the
subspecies _R. m. orinus_ as mapped by Hooper (1952:141), coming from a
locality to the southeast of the two westernmost localities shown by
him for _orinus_. This mouse is distinctly darker than any of the
specimens of _orinus_ discussed beyond, and is as dark as the darkest
_howelli_ seen by us. In addition to the specimens of _howelli_ listed
above, we have examined 12 from Prusia, Chiapas (UMMZ 88351-58,
96810-13), and three from 3 mi. NW San Cristóbal, Chiapas (KU
66680-82).

_R. m. howelli_ may occur at moderate elevations along the coast of
southern Guatemala, or possibly this specimen represents a population
of dark-colored mice that is isolated from similarly colored
populations to the north and west. According to the field notes of
Albert A. Alcorn, the collector, this specimen was taken in a "tree
set." Perhaps pale-colored and dark-colored populations of _R.
mexicanus_ are sympatric but ecologically segregated in this region.

~_Reithrodontomys mexicanus lucifrons_~ Howell.--NICARAGUA.--Jinotega:
1 mi. NW Jinotega, 1 (KU 71344--April 12, 1956); 5 mi. S, 2 mi. E
Jinotega, 1 (KU 71343--April 12, 1956).

Comments on these specimens have appeared earlier (Englert, 1959:153).

~_Reithrodontomys mexicanus orinus_~ Hooper.--GUATEMALA.--Guatemala: 5
mi. S Guatemala City, 4950 ft., 2 (KU 65388-89--March 11, 1955); 6 mi.
S Guatemala City, 4680 ft., 3 (KU 65390-92--March 10, 1955); 7 mi. S,
6 mi. E Guatemala City, 5800 ft., 2 (KU 65393-94--March 14, 1955).

Our seven specimens are from near the northwestern edge of the
geographic range of _orinus_ (where it meets that of _howelli_) as
mapped by Hooper (1952:141). Nevertheless, they are distinctly brighter
dorsally, paler ventrally, and average larger than the specimens listed
in the account of _R. m. howelli_ above. Also, they match well in size
and coloration the specimens from nearby Lago de Amatitlan (USNM
275406-09) and Finca San Rafael (CNHM 41770) that were referred by
Hooper to _R. m. orinus_. He (_op. cit._:149) noted that these
last-mentioned specimens were slightly darker than topotypes of
_orinus_ and differed from them in several minor cranial features,
which he interpreted as evidence of intergradation with _howelli_.

~_Reithrodontomys brevirostris_~ Goodwin.--COSTA RICA.--Alajuela: 5 mi.
SW San Ramón, 1 (KU 71362--July 11, 1956). NICARAGUA.--Carazo: 3 mi.
NNW Diriamba, 2 (KU 71390-91--June 16, 21, 1956).

External measurements of these three specimens are respectively: total
length, 179, 167, 173; length of tail, 107, 96, 101; length of hind
foot, 19, 18, 18; length of ear from notch, 15, 13, 13. The teeth show
about the same moderate wear in each of the three specimens. Our
_brevirostris_ differ noticeably from specimens of _Reithrodontomys
mexicanus cherriei_ and _R. m. lucifrons_ that we have seen in duller,
darker, and less reddish color. One specimen, KU 71390, still has a
patch of gray juvenal pelage on the nape; the newer pelage elsewhere is
shorter and sparser than that of the other two specimens. In addition,
No. 71390, a female, contained no embryos, but has two pairs of mammae,
one pair pectoral and one inguinal, that are conspicuous on the dried
skin; perhaps this female was lactating when captured. The mammae of KU
71362, also a non-pregnant female, are inconspicuous on the dried skin.
The Nicaraguan specimens extend the known geographic range
approximately 270 kilometers northwestward from near Villa Quesada,
Alajuela, Costa Rica, and are the first records of the species from
Nicaragua.




LITERATURE CITED


ENGLERT, D. C.

     1959. First records of two species of harvest mice in
           Nicaragua. Southwestern Nat., 4:153, October 24.

FELTON, H.

     1958. Nagetiere (Mammalia, Rodentia) aus El Salvador, Teil
           2. Senckenbergiana Biologica, 39 (1/2):1-10, 1 fig.,
           March 31.

HOOPER, E. T.

     1952. A systematic review of the harvest mice (genus
           _Reithrodontomys_) of Latin America. Miscl. Publ.
           Mus. Zool., Univ. Michigan, 77:1-225, 9 pls., 24
           figs., 12 maps, January 16.

_Transmitted October 1, 1959._




       *       *       *       *       *

Transcriber's Notes:

Bold text is shown within ~tildes~.

Italicized text is shown within _underscores_.

Bold italicized text is shown within ~_tildes and underscores_~.