Biology ETDs

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The ecological distribution of the four species of spiny lizards (Scelouorus) occurring in Big Bend National Park, Texas, was studied in the summers of 1968 and 1969. A total of 219 lizards was observed or collected by shooting with a pistol or rubber bands, by hand, and by use of can traps. The most abundant species was S. merriami (92 specimens observed or collected), second was S. poinsetti (63 specimens), third was s. magister (38 specimens), and least abundant was S. undulatus (26 specimens). Five general communities are described: Rio Grande flood­plain, desert scrub, desert grassland, pinyon-juniper-oak woodland, and ponderosa pine-Douglas-fir-Arizona cypress forest. Habitats within each are described on a vegetational or physiographic basis. The largest number of species and individuals of Scelonorus was observed in the desert scrub community (138 specimens) and the least number in the ponderosa pine-Douglas-fir-Arizona cypress forest (3 specimens). Competition and habitat displacement within the genus Scelonorus and between Sceloporus and other iguanid lizards are discussed in relation to the abundance of preferred habitat. No species of Scelonorus was restricted to only one community; except for S. magister, the species ranged into four communities each. No species was found in all communities. Similarities in ecological distribution of Scelonorus and Cnemidonhorus (whiptail lizards) were noted in the park and are discussed.



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First Committee Member (Chair)

William George Degenhardt

Second Committee Member


Third Committee Member

William Jacob Koster

Fourth Committee Member

J. David Ligon

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