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The Mammals
of Texas - Online Edition GEOGRAPHIC DISTRIBUTION OF LAND MAMMALS Texas may be conveniently arranged into four regions based on the ecological distribution of mammals. These are the Trans-Pecos, Plains Country, East Texas, and the Rio Grande Plains (Figure 4). The Trans-Pecos region includes the mountain and basin country west of the Pecos River. The Plains Country includes the High Plains, Rolling Plains, Cross Timbers area, and the Edwards Plateau. Included within the East Texas region are the Pineywoods, central Texas Woodlands, Blackland Prairies, and Coastal Prairies and Marshes. The Rio Grande Plains encompasses the South Texas brushlands. The Balcones Escarpment serves as the major physiographic barrier separating the Plains Country from East Texas and the Rio Grande Plains. The boundary between East Texas and the Rio Grande Plains is positioned between the Guadalupe and San Antonio rivers where pedocal and pedalfer soils meet. The distributional patterns of land mammals in Texas conform to five major patterns. These are: (1) ubiquitous species that range throughout most, or all, of the state (included in this group are several species that are now extinct or whose distributions have shrunk markedly in the past 150 years); (2) species that are distributed primarily in one of the four divisions of the state; (3) western species distributed in the Trans-Pecos and Plains Country; (4) western species distributed in the Trans-Pecos and Plains Country, but which also occur on the South Texas Plains; and (5) eastern species distributed principally east of the 100th meridian. Mammals assigned to each of these categories are listed. It should be noted that certain species occur slightly outside of the boundaries of the category to which they have been assigned. The greatest number of unique elements in the mammal fauna of Texas occur in the Trans-Pecos region. Almost one-third of the 92 species of mammals that occur in the Trans-Pecos are primarily restricted in distribution to that region. Most of these mammals are species characteristic of the arid Mexican Plateau and southwestern United States or the montane woodlands of the western United States. The fewest number of unique elements is found in the Plains Country. The 15 mammals unique to East Texas are species characteristic of the deciduous forests and coastal prairies of the southeastern United States, which reach their western distributional limits in Texas. The Rio Grande Plain supports 11 unique elements, most of which are characteristic of the tropical lowlands of northeastern Mexico and reach their northern distributional limits in south Texas. MAMMALS GENERALLY DISTRIBUTED THROUGHOUT THE STATE:
MAMMALS OCCURRING PRINCIPALLY IN THE TRANS-PECOS:
MAMMALS OCCURRING PRINCIPALLY IN THE PLAINS COUNTRY:
MAMMALS OCCURRING PRINCIPALLY IN THE RIO GRANDE PLAINS:
MAMMALS OCCURRING PRINCIPALLY IN EAST TEXAS:
MAMMALS OCCURRING
PRINCIPALLY IN WEST TEXAS
MAMMALS OCCURRING
PRINCIPALLY IN WESTERN TEXAS
MAMMALS OCCURRING PRINCIPALLY EAST OF THE 100TH MERIDIAN:
Five species of mammals (all rodents) are unique to Texas in the sense that most, or all, of their known geographic range is confined to the mainland part of the state. These are:
There are three species of mammals (Diphylla ecaudata, Myotis lucifugus, Myotis septentrionalis) whose occurrence in Texas may be regarded as accidental. Resident breeding populations of these species probably never existed within the state. The Texas records for all three are far outside of their main range and only a single record exists for each in the state. Furthermore, all three are bats which are well known for their wandering movements. Other topics under Texas Mammals:
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