Characterization of adjacent desert mule and white-tailed deer habitats in West Texas
Fourteen vegetative parameters and a Land Surface Ruggedness Index (LSRI) were quantified on 306,000 ha of rangeland that differentially supported high and low densities of mule deer (Odocoileus hemionus crooki) and white-tailed deer (0. Virginianus texanus) in west Texas to evaluate species-specific habitat parameters. The only significantly different (P<0.05) vegetative component between the habitats of the 2 species was percent woody cover. On the high density white-tailed deer habitats, woody cover averaged 63/E, and on the high density mule deer habitats i t averaged 43%. Increases in white-tailed deer densities were positively correlated with increases in percent woody cover. The relationship between woody cover and responses in desert mule deer numbers was not significant (P>0.05), but desert mule deer numbers tended to decrease as percent woody cover increased. Mule deer recently disappeared from 2 areas where woody cover exceeded 75?. The measurement of percent woody cover correctly classified 83 and 65% of the study areas into high and low density classes, respectively, for white-tailed deer and desert mule deer. The threshold value for discriminating between habitats of high or low deer density was approximately 53 and 50% woody cover for white-tailed deer and mule deer, respectively.
Average LSRI values where white-tailed deer were sighted during aerial surveys were less than where desert mule deer were sighted. The LSRI for mule deer ranged from 2 to 232 and for white-tailed deer from 0 to 136. In areas exhibiting a wide variance in topographic ruggedness white-tailed deer appeared to be restricted to locations of lesser ruggedness, but mule deer were not. Coexistence of desert mule deer and white-tailed deer in west Texas is possible because of their divergent habitat selection for percent woody cover and topography. However, because woody cover can change temporally, the possibility exists for competitive exclusion to occur as deer densities shift in response to changes in woody cover. Competitive exclusion apparently has occurred in west Texas as white-tailed deer have successfully supplanted mule deer in localized areas. Monitoring of changes in woody cover should be used as an a priori method for identifying areas where the potential for competitive exclusion exists. The use of habitat manipulative practices that can rebalance the ratio of preferred habitats for each deer species seems essential to ensure the continued presence of both species in this portion of their range.