Population Reactions of Selected Game Species to Aerial Herbicide Applications in South Texas

Abstract

Highlight: Aerial spraying 80% of a mature honey mesquite brushland in alternating strips with 2,4,5-T + picloram (1:l) at 1.12 kg/ha did not adversely affect populations of white-tailed deer, nilgai antelope, wild turkeys, or feral hogs. Complete treatment (100% sprayed) apparently exceeded the threshold of suitability for all game species surveyed except niigai antelope. White-tailed deer densities were inversely correlated with production and species diversity of forb populations following aerial spraying. With restoration of the forbs at 27 months after treatment, there were no differences among treatments in deer numbers. Javelina populations, apparently as a result of controlling pricklypear, were significantly reduced by both spray treatments. Reductions in javelina densities were apparent at the final census, 27 months after herbicide application. The term, ‘ ‘range management, ’ ’ generally connotes increasing the grazing capacity of rangeland. During the past century, much of the rangeland of South Texas has become “thicketized” by the increased density and stature of woody species (Johnston 1962), reducing its productivity for livestock. Extensive brush control efforts have been employed to check woody-plant encroachment and increase grass production for domestic livestock (Lehmann 1960). Range improvement efforts in the Rio Grande Plain of Texas have been characterized by mechanical brush control often followed by conversion of land use to tame pasture. Only recently have game animals been considered of adequate economic importance for incorporation of their habitat requirements into range improvements programs. As their economic value has increased (Teer and Forrest 1968), the impact of range improvement practices on game animal habitat has emerged as a critical variable for consideration in proposed vegetation manipulation schemes. The structure and composition of vegetation, particularly the relative proportions of various woody and herbaceous components, determine habitat quality for game species. Alterations of vegetative cover serve to either accelerate or retard plant