Sul Ross State University

Small Mammal, Herpetofauna and Avian Communities
of the O2 Ranch, Brewster County, Texas

by Suzanne Contreras, Bonnie Warnock and Louis A. Harveson

As part of a faunal baseline survey on the O2 Ranch, Brewster and Presidio counties, Texas, small mammals, herpetofauna and avian communities were inventoried at Duff Springs. A total of 272 individuals small mammals were trapped by Sherman live traps in 3,960 trap-nights from 1 January to 31 August 2003.

Small mammal trap success was 6.87 captures/100 trap-nights. Relative abundance for small mammals was 6.93 captures/100 trap-nights.

Dipodomys merriami was the most abundant species by percent of total captures. Peromyscus maniculatus was the only species distributed across all vegetation types. Four small mammal species, D. ordii, P. leucopus, Onychomys arenicola and Sigmodon hispidus were specific to a single vegetation type.

Ninety-five individuals representing 10 herpetofauna species were sampled by a standard array system in 84 array-nights from June to August 2003.

Herpetofauna relative abundance was 113.49 captures/100 array-nights. Cophosaurus texanus was the most abundant herpetofauna species on Duff Springs.

Three species, C. texanus, Cnemidophorus tigris and Bufo punctatus, were found in all months and vegetation types. Four species, Phrynosoma modestum, Sceloporus poinsetti, C. tesselatus and B. debilis, were unique to a particular vegetation type.

Twenty-four species, representing 416 bird detections, were recorded in 154 fixed-radius point counts conducted from 1 February to 31 August. The most abundant bird species was black-throated sparrow (Amphispiza bilineata).

Four species, the black-throated sparrow, northern mockingbird (Mimus polyglottos), mourning dove (Zenaida macroura and scaled quail (Callipepla squamata) were distributed among all vegetation types. Six species, turkey vulture (Carthartes aura), northern flicker (Colaptes auratus), ruby-crowned kinglet (Regulus calendula), Wilson’s warbler (Wilsonia pusilla), brown-headed cowbird (Molothrus ater) and house finch (Carpodacus mexicanus) were unique to a single vegetation type.

Although data are descriptive, they provide insight into animal community structure and dynamics. Repeated faunal survey should allow resource managers to evaluate faunal responses to habitat management scenarios.

Cooperative funding provided by the Lykes Foundation, Sul Ross State University and the San Antonio Livestock Exposition.