This species is probably the most common rodent in Tamaulipas. It was
taken at almost every locality sampled and was associated with many
other kinds of rodents. Its distribution is state-wide with the
exception of the extreme northwestern part. Two subspecies are
represented in Tamaulipas, _L. i. alleni_, which occurs in the western
side of the Sierra Madre Oriental in the southwest part of the state,
and _L. i. texensis_, which occupies the rest of the range of the
species in the state.
At Soto la Marina specimens were taken in dense brush, around the
cultivated fields; no burrows were seen and all specimens were trapped
before 10:00 p.m. On the Sierra de Tamaulipas, _Liomys_ was collected
in practically all microhabitats. In the vicinity of San Fernando,
individuals were trapped in a dry area in which vegetation consisted of
mesquite, cactus and chollas; the ground there was covered with dry
leaves and small sticks, and burrows were found near the base of the
mesquite bushes. One specimen was taken near the house of a woodrat.
Two kilometers west of El Carrizo, where _Liomys irroratus_ is called
"raton tuza," specimens were collected on rocks inclined at an angle of
about twenty-five degrees that were covered with zacaton grass and
some bushes. Some individuals were taken in a sugar cane field that was
surrounded by bushes and tall grass; _Baiomys taylori_, _Sigmodon
hispidus_, and _Peromyscus leucopus_ were taken in the line of traps.
One specimen was caught in a trap baited with banana.
Some dates concerning reproduction of _Liomys irroratus_ in Tamaulipas
are as follows: La Pesca, May 25, one female lactating and one female
pregnant with 4 embryos that measured 8 mm.; Jaumave, July 26-29, three
females lactating and three pregnant females that carried 6 embryos (6
mm.), 6 embryos (15 mm.), and 5 embryos (15 mm.); Palmillas, July 23, a
female with 1 embryo measuring 6 mm.; Nicolas, October 19, a female
carrying 4 embryos measuring 3 mm.
=Liomys irroratus alleni= (Coues)
1881. _Heteromys alleni_ Coues, Bull. Mus. Comp. Zool.,
8:187, March, type from Rio Verde, San Luis Potosi.
1911. _Liomys irroratus alleni_, Goldman, N. Amer. Fauna,
34:56, September 7.
_Distribution in Tamaulipas._--Extreme southwestern part of
state.
This subspecies is easily distinguished from _L. i. texensis_ by the
following features: hind foot larger, 31.5 (30-33.5) instead of 27.8
(27-29); skull longer, 34.2 (32.4-36.4) instead of 31.5 (30.0-32.5);
maxillary tooth-row longer, 5.4 (5.0-5.8) instead of 5.0 (4.8-5.1);
interorbital constriction relatively narrower in _alleni_.
Intergradation between _L. i. alleni_ and _L. i. texensis_ takes place
at Rancho Santa Rosa (where, of the two specimens, one is conspicuously
larger than the other), eight kilometers northeast of Antiguo Morelos,
El Encino, and Ejido Santa Isabel. All specimens from the localities
mentioned are here assigned to _texensis_.
Weight of three pregnant females averaged 68.9 (64-78) grams, that of
non-pregnant females, 65.6 (64-68), and that of six males 73.0 (65-80).
_Records of occurrence._--Specimens examined, 34: Villa
Mainero, 1700 ft., 2; Nicolas, 56 km. NW Tula, 5500 ft., 6;
Jaumave, 2400 ft., 23; 16 mi. N, 6 mi. W Palmillas, 5500
ft., 1; 14 mi. N, 6 mi. W Palmillas, 5500 ft., 2.
Additional records: Miquihuana (Goldman, 1911:56); Tula
(Hooper and Handley, 1958:18).
=Liomys irroratus texensis= Merriam
1902. _Liomys texensis_ Merriam, Proc. Biol. Soc.
Washington, 15:44, March 5, type from Brownsville, Cameron
Co., Texas.
1911. _Liomys irroratus texensis_, Goldman, N. Amer. Fauna,
34:59, September 7.
_Distribution in Tamaulipas._--State-wide except extreme
southwestern and northwestern parts.
Intergradation occurs between _L. i. texensis_ and _L. i. pretiosus_ in
southeastern Tamaulipas as noted previously by Hooper (1953:5).
Individuals from Altamira and one mile south thereof are small and dark
as in _pretiosus_, but cranial measurements are as in _texensis_ to
which they are here assigned. Specimens from the vicinity of Tampico
are typical _texensis_.
Average weight of the specimens from three different localities are as
follows: Soto la Marina, seven males, 42.7, 14 females, 36.9; Sierra de
Tamaulipas, 12 males, 47.3, 20 females, 40.7; Sierra Madre Oriental,
eight males, 45.5, nine females, 37.0 grams.
The specimens reported by Ingles (1959:394) from two miles south of El
Mante as _L. irroratus_ are here referred to _texensis_ on geographic
grounds.
_Records of occurrence._--Specimens examined, 121: 7 km. S,
2 km. W San Fernando, 7; 7 km. SW La Purisima, 1; Rancho
Santa Rosa, 25 km. N, 13 km. W Cd. Victoria, 260 m., 2; 36
km. N, 10 km. W Cd. Victoria, 1; 15 mi. N Cd. Victoria, 2; 4
mi. N La Pesca, 5; Soto la Marina, 25; Sierra Madre
Oriental, 5 mi. S, 3 mi. W Cd. Victoria, 1900 ft., 18;
Sierra de Tamaulipas, 2 mi. S, 10 mi. W Piedra, 1200 ft.,
36; Sierra de Tamaulipas, 3 mi. S, 10 mi. W Piedra, 1200
ft., 1; Ejido Santa Isabel, 2 km. W Pan-American Highway,
2000 ft., 3; Rancho Pano Ayuctle, 25 mi. N, 3 km. W El
Mante, 300 ft., 1; Rancho Pano Ayuctle, 6 mi. N Gomez
Farias, 300 ft., 8; 10 km. N, 8 km. W El Encino, 400 ft., 1;
2 km. W El Carrizo, 6; 53 km. N El Limon, 4; 8 km. NE
Antiguo Morelos, 2; Altamira, 1; 1 mi. S Altamira, 3; 10 mi.
NW Tampico, 1; 7 km. N Tampico, 2.
Additional records: Hidalgo (Goldman, 1911:59); Matamoros
(_ibid._); Bagdad (_ibid._); Sierra de San Carlos (Hooper
and Handley, 1948:20); 3 mi. W Soto la Marina (Hooper,
1953:5); [Cd.] Victoria (Goldman, 1911: 59); Acuna (Hooper
and Handley, 1948:20); Mesa de Llera (Hooper, 1953:5); Gomez
Farias (Goodwin, 1954:9); 2 mi. S Cd. Mante (Ingles,
1959:394); Antiguo Morelos (Hooper and Handley, 1948:20).
=Castor canadensis mexicanus= V. Bailey