Effects of Grazing on the Demography and Growth of the Texas Tortoise

摘要: : Considerable effort has been exerted in attempts to understand the complex ecological effects of grazing. North American tortoises, by virtue their distribution, provide a good model taxon through which study how grazing vary with regime, habitat, and climate. We studied Texas tortoise ( Gopherus berlandieri ), is restricted primarily privately owned rangelands southern northeastern Mexico. Management this species hampered lack information on common land-use practices. evaluated moderate cattle (short-duration, winter-spring rotational regime; 6–28 animal-unit days/ha/year) comparing two grazed ungrazed sites Western Rio Grande Plains, ( U.S.A.), from April 1994 October 1997. made 132 captures 106 individuals pastures 324 237 pastures. also radiotracked 22 tortoises 25 Comparisons relative abundance, body-size age body mass, sex ratio, adult survival, proportion juveniles, growth rates revealed no differences ( p> 0.05 for all parameters) between areas. Based these results, we suggest that not incompatible maintenance populations. Our data were consistent general biogeography tolerance disturbance suggests are tolerant intermediate levels disturbance. Generalities about effect four should be avoided unless they can placed context precipitation, habitat quality, requirements. Resumen: Se realizan esfuerzos considerables para intentar entender los complejos efectos ecologicos del pastoreo. Las tortugas terrestres de Norte America, en virtud su distribucion, son un buen modelo estudiar la variacion pastoreo funcion regimen pastoreo, el y clima. Estudiamos Tortuga (Gopherus berlandieri) que esta restringida principalmente pastizales privados sur noreste El manejo especie limitado por falta informacion sobre las practicas comunes uso suelo. Evaluamos moderado (corta duracion, primavera-verano, rotacion unidades-animal dias/ha/ano) tortuga comparando dos sitios con sin abril octubre Realizamos capturas individuos Tambien colocamos transmisores La comparacion abundancia relativa, distribucion tamano corporal, edades, masa proporcion sexos, supervivencia adultos, juveniles tasas crecimiento revelo diferencias (p> todos parametros) entre Con base estos resultados, sugerimos es mantenimiento poblaciones Tortugas Texas. Nuestros datos fueron consistentes biogeografia tolerancia perturbacion sugiere tolerantes niveles intermedios perturbacion. deben evitar generalizaciones efecto cuatro especies menos se coloquen contexto precipitacion, calidad requerimientos tortugas.