The Recent Mammals of Tamaulipas, Mexico.

by Ticul Alvarez.

INTRODUCTION

From Tamaulipas, the northeasternmost state in the Mexican Republic, 146 kinds of mammals, belonging to 72 genera, are here reported.

Mammals that are strictly marine in habit are not included. The state is crossed in its middle by the Tropic of Cancer. Elevations vary from sea level on the Golfo de Mexico to more than 2700 meters in the Sierra Madre Oriental; most of the state is below 300 meters in elevation. Its area is 79,602 square kilometers (30,732 square miles).

Tamaulipas, meaning "lugar en que hay montes altos" (place of high mountains), was explored in 1516 by the Spaniard Francisco Fernandez de Cordoba, but it was not until the 18th century that Jose de Escandon established several villages in the new province of Nueva Santender from which, in the time of Iturbide's Empire, Tamaulipas was separated as a distinct political ent.i.ty, with about the same boundaries that it now has.

My first contact with the state of Tamaulipas, as a mammalogist, was in 1957, when in company with Dr. Bernardo Villa R. I visited the Cueva del Abra in the southern part of the state. On several occasions since then I have been in the state, especially when employed by the Direccion General de Caza of the Mexican Government. In 1960-1962 I had the opportunity of studying the mammalian fauna of Tamaulipas at the Museum of Natural History of the University of Kansas. The approximately 2000 specimens there represent many critical localities, but are not sufficient to make this report as complete as could be desired. Consequently the following account should be considered as a contribution to the knowledge of the mammals of Mexico and is offered in the hope that it will stimulate future studies of the Mexican fauna, especially that of the eastern region.

PHYSIOGRAPHY

Tamaulipas can be divided into three physiographic regions, which from east to west are Gulf Coastal Plain, Sierra Madre Oriental, and Central Plateau or Mexican Plateau (Fig. 1).

Gulf Coastal Plain

This physiographic region covers most of the state and extends northward into Texas and a short distance southward into Veracruz.

According to Tamayo (1949) and Vivo (1953), the Gulf Coastal Plain is formed by sedimentary rocks from Mesozoic to Pleistocene in age. The most common type of soil is Rendzin, especially in the coastal area.

Elevations range from sea level to 300 meters. The area is in general a flat plain inclined to the sea but this plain is broken by several small sierras. The more important of these are the Sierra de Tamaulipas, which rises to more than 1000 meters, and the Sierra San Carlos, which has a maximum elevation of approximately 1670 meters. The Sierra de San Jose de las Rucias is smaller.

Sierra Madre Oriental

This physiographic region is represented in Tamaulipas by a small part of the long Sierra Madre Oriental that extends from the Big Bend area in Texas southward to the Trans-volcanic Belt of central Mexico. The Sierra Madre Oriental is in the southwestern part of Tamaulipas. The Sierra was formed by folding of the Middle and Upper Cretaceous and Cenozoic deposits that now are 400 to 2700 meters in elevation. In general, the soils are Chernozems.

This physiographic region is situated between the other two physiographic regions in Tamaulipas and represents a barrier to the distribution of some tropical mammals on the one hand and to those from the Mexican Plateau on the other.

[Ill.u.s.tration: FIG. 1. Three physiographic regions: 1 Coastal Plain; 2 Sierra Madre Oriental; 3 Central Plateau.]

Central Plateau

This physiographic region, commonly termed the Mexican Plateau, occupies only a small area of Tamaulipas in its southwesternmost part.

The plateau is approximately 900 meters above sea level. In general, the Mexican Plateau was formed by Cretaceous sediments. The most common type of soil is Chestnut.

CLIMATE

Owing to the differences in elevations and varying distances from the sea, the climate of Tamaulipas is varied. Tamayo (1949), following the Koeppen System, a.s.signed to Tamaulipas 10 different climate types that result princ.i.p.ally from differences in temperature, precipitation, and humidity.

Temperature

The annual mean temperature for the lands less than 1000 meters in elevation, which make up most of the state, is between 20 and 25 C.; and the difference in monthly means is 5 C.

In the areas above 1000 meters, the annual mean is between 15 and 20 C., and the difference in the monthly means is 15 C.

The maximum temperature recorded in the state is 45 C. in the region of Ciudad Victoria, between the Sierra Madre Oriental, the Sierra San Carlos, and the Sierra de Tamaulipas. Minima recorded are between O and 5 C. on the southeastern coast, O to -5 C. between 98 20' long.

and 99 00' long., and -5 to -10 C. in the Sierra Madre Oriental.

Precipitation

Rainfall varies seasonally and can be described as follows: In January it amounts to 25 to 50 mm. in the coastal region and 10 to 25 mm. in the rest of the state. In April there is more than 25 mm. to the north of about 23 north lat.i.tude, 10 to 25 mm. in the Sierra de Tamaulipas and Sierra Madre Oriental, and less than 10 mm. in the extreme southwestern part of the state.

In July rainfall amounts to less than 25 mm. in Nuevo Laredo and San Fernando, is from 25 to 50 mm. in the northeastern and central parts of the state, 50 to 100 mm. in the Sierra San Carlos and Sierra Madre Oriental, and 100 to 200 mm. in the area south of Soto la Marina and east of the Sierra Madre Oriental. In October rainfall is less than 50 mm. in the northern half of the state, including the Sierra de Tamaulipas, and 50 to 100 mm. in the rest of the state, except on the east side of the Sierra Madre Oriental and in the area near Tampico, which receive between 100 and 200 mm.

The number of rainy days per year varies from 60 to 90 at Sierra San Carlos, Sierra Madre Oriental, and in the lowlands south of 23 north lat.i.tude; the rest of the state has about 60 rainy days, excepting the Mexican Plateau, which has fewer than 60.

Although Tamayo (1949) followed the Koeppen System in cla.s.sifying types of climate and thereby recognized 10 different kinds of climate in Tamaulipas, these can be grouped into three major categories as follows:

Steppe Dry Climate (Clima Seco de Estepa)

This kind of climate can be divided into two categories based on the average annual temperature.

_Warm_

The average annual temperature exceeds 18 C. but the mean of the coolest month is less than 18 C. This sub-climate is characterized by a short rainy season in summer and occurs on the west side of the southern part of the Sierra Madre Oriental and on the Mexican Plateau; it occurs also in the area northwest of Reynosa and on the east side of the Sierra Madre Oriental but in these areas the rainfall is irregularly distributed in the year.

_Cool_

The average annual temperature is less than 18 C. but the mean of the warmest month exceeds 18 C. This sub-climate occurs only on the west side of the northern part of the Sierra Madre Oriental.

Moderate Rainy Temperature Climate (Clima Templado Moderato Lluvioso)

This type of climate is characterized by the coolest month having a temperature of between -3 and 18 C. In the northeastern and central parts of Tamaulipas, including the Sierra de Tamaulipas, Ciudad Victoria, Gomez Farias, Rancho Pano Ayuctle, and Llera, the average temperature of the warmest month is less than 22 C.; the winters are dry and not rigorous, and the wettest month has ten times as much rain as the driest. In the Sierra San Carlos the average temperature of the warmest month is less than 22 C., and the rainy season is in the autumn.

Tropical Rainy Climate (Clima Tropical Lluvioso)

This climate is characterized by the average temperature of all months being above 18 C. and the mean-annual rainfall being above 75 cm.