This is the most common species of _Reithrodontomys_ in Tamaulipas; it
occurs in almost all parts of the state, from sea level to high up in
the mountains and from the tropical forest to the desert plain.
The three subspecies in the state are _R. f. intermedias_ in the
northern half, _R. f. griseoflavus_ in the high parts of the Sierra
Madre Oriental, and _R. f. tropicalis_ in the southeast. The lines
between these subspecies are difficult to establish because the zones
of intergradation are broad. Characters for separating the three
subspecies in Tamaulipas are listed by Hooper (1952).
=Reithrodontomys fulvescens griseoflavus= Merriam
1901. _Reithrodontomys griseoflavus_ Merriam, Proc.
Washington Acad. Sci., 3:553, November 29, type from Ameca,
4000 ft., Jalisco.
1952. _Reithrodontomys fulvescens griseoflavus_, Hooper,
Miscl. Publ. Mus. Zool., Univ. Michigan, 77:98, January 16.
_Distribution in Tamaulipas._--Known only from Jaumave.
Only specimens from Jaumave are clearly _R. f. griseoflavus_; all
others east of this locality are intergrades between _griseoflavus_ and
_tropicalis_, under which latter subspecies they are included. In
_griseoflavus_ the tail is longer in relation to the head and body,
141.2 (135-153) per cent, than in the other two subspecies that occur
in Tamaulipas. The average weight of 14 males was 14 (12-16) grams.
_Record of occurrence._--Specimens examined, 15, from
Jaumave, 2400 ft.
=Reithrodontomys fulvescens intermedius= J. A. Allen
1895. _Reithrodontomys mexicanus intermedius_ J. A. Allen,
Bull. Amer. Mus. Nat. Hist., 7:136, May 21, type from
Brownsville, Cameron Co., Texas.
1914. _Reithrodontomys fulvescens intermedius_, A. H.
Howell, N. Amer. Fauna, 36:47, June 5.
_Distribution in Tamaulipas._--Northern half of state.
No specimen of this subspecies has been examined. Jones and Anderson
(1958:447) reported specimens from Rancho Pano Ayuctle as _R. f.
intermedius_, but here those same specimens are assigned to _R. f.
tropicalis_. J. A. Allen (1891:223) recorded specimens from Santa
Teresa as _Ochetodon mexicanus_. According to Hooper (1952:142) that
name was used by Allen for _R. fulvescens_. Allen's specimens from
Santa Teresa are here referred to _R. f. intermedius_ on geographic
grounds.
_Records_ (Hooper, 1952:108): Camargo, 200 ft.; 20 mi. S
Reynosa, Charco Escondido; Matamoros, 30 ft.; 7.5 mi. S
Matamoros; 29 mi. S Cd. Victoria, 800 ft.; Hacienda Santa
Engracia, 800 ft.; Santa Teresa (50 mi. SW Matamoros);
Sierra San Carlos (El Mulato, Tamaulipeca, 1500 ft.).
=Reithrodontomys fulvescens tropicalis= Davis
1944. _Reithrodontomys fulvescens tropicalis_ Davis, Jour.
Mamm., 25:393, December 12, type from Boca del Rio, 8 km. S
city of Veracruz, Veracruz.
_Distribution in Tamaulipas._--Tropical area in southeastern
part of state.
Most of the specimens examined of _R. fulvescens_ are included in this
subspecies, principally because of their reddish coloration that is
characteristic of _R. f. tropicalis_. According to the original
description by Davis (1944:393) this subspecies is smaller than
_griseoflavus_ and the posterior border of the incisive foramina
terminate anterior to the plane of the molars. But, these
characteristics are not found in any specimen examined from Tamaulipas
and the average of external measurements is more than those given by
Hooper (1952:109) for _tropicalis_. Of all specimens from Tamaulipas,
those from the vicinity of Altamira and Tampico are most nearly typical
of _tropicalis_. Weights of seven males and five females, from the
Sierra de Tamaulipas, were, respectively, 13 (11-15), and 11 (9-14)
grams.
_Records of occurrence._--Specimens examined, 51: Rancho
Santa Rosa, 25 km. N, 13 km. W Cd. Victoria, 1; Cd.
Victoria, 3; Sierra de Tamaulipas, 10 mi. W, 2 mi. S Piedra,
1200 ft., 12; 2 km. W El Carrizo, 1; Ejido Santa Isabel, 2
km. W Pan-American Highway, 2000 ft., 14; Rancho Pano
Ayuctle, 25 mi. N, 3 km. W El Mante, 300 ft., 4; Rancho Pano
Ayuctle, 6 mi. N Gomez Farias, 300 ft., 4; 6 mi. N, 6 mi. W
Altamira, 2; 1 mi. S Altamira, 3; 16 km. N Tampico, 3; 7 km.
N Tampico, 4.
Additional records: Hidalgo (Hooper, 1952:110); 5 mi. NE
Gomez Farias, 1100 ft. (_ibid._); La Azteca, 5 km. NNE Gomez
Farias (Goodwin, 1954:11); Gomez Farias (_ibid._); Antiguo
Morelos (Hooper, 1952:110); 2 mi. W Tampico (Ingles,
1959:396).
=Reithrodontomys mexicanus mexicanus= (Saussure)