Simulation modeling of big game at Wichita Mountains Wildlife Refuge
Date
1977
Authors
Williams, Gary Leroy, author
Gross, Jack E., advisor
Hein, Dale A., committee member
Wunder, Bruce A., committee member
Brown, Perry J., committee member
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Volume Title
Abstract
Certain aspects of the population ecology of herds of bison (Bison bison), elk (Cervus canadensis), white-tailed deer (Odocoileus virginianus), and Texas longhorn cattle (Bos taurus) inhabiting the Wichita Mountains Wildlife Refuge in southwestern Oklahoma were investigated by analyzing data contained in existing refuge reports and related documents. The information obtained was subsequently used in validation studies for a simulation model (Program ONEPOP) designed to mimic the dynamics of big game grazing systems. The factors which influenced population sizes most in the four populations were harvest rate of the previous year and reproductive rate. In all four populations, natural mortality rates tended to be density independent whereas reproductive rates were density dependent. Ecological factors which influenced herd reproductive rates were precipitation amount and food supply. The amount of precipitation received during August and September, immediately prior to and during the breeding period, may have had greater influence on re-productive rates than total annual precipitation. Incidence of pregnancy among yearling females was especially high during years of above-average precipitation. There was also evidence that lactation status affected reproductive rates in elk. In general, there was an inverse relation between lactation and pregnancy among Wichita elk. Computer simulations with Program ONEPOP closely mimicked reported values for population size and trend, reproductive parameters, harvest, and sex and age structures in the bison and longhorn cattle populations. Simulated population sizes for elk, however, were substantially higher than corresponding reported values and led to the conclusion that the Wichita elk population had been underestimated for several years. Demographic data for white-tailed deer were too poor to adequately test the model. Results indicated that Program ONEPOP simulated big game population dynamics with a high degree of precision and realism. The model contained the basic parameters which produced population changes over time and was consistent with population controlling mechanisms. The model appeared to have the capability of generating information useful in herd management.
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Subject
Wildlife refuges -- Oklahoma -- Wichita Mountains
Wildlife refuges -- Simulation methods