Ecological relationships between mule deer and white-tailed deer in southeastern Arizona USA.

Anthony, R.; Smith, N.

Niche relationships between the desert mule deer (Odocoileus hemionus crooki) and Coues white-tailed deer (O. virginanus couesi) were studied in the San Cayetano and Dos Cabezas mountains in the southeastern Arizona (USA) from Sept. 1969-March 1972. Walk transects were established on the study areas on which deer were observed. Altitude, slope exposure and habitat selection were used to describe distributional patterns of the 2 spp. Food habits were studied by analyzing fecal samples microscopically for epidermal fragments of important forage plants. Behavioral interaction between mule deer and white-tailed deer, browse utilization on Cercocarpus breviflorus, and recruitment were also investigated. Spatial distributions according to altitude and slope exposure indicated that a buffer zone existed between populations of mule deer and white-tailed deer in the San Cayetano Mountains. Mule deer were associated with fewer vegetational types than white-tailed deer on this study area. There was much overlap in food preferences of mule deer and white-tailed deer (55-67% seasonally). Populations of mule deer and white-tailed deer were sympatric in the Dos Cabezas Mountains; the coefficients of association were highly positive. There was also a great similarity in habitat selection between the 2 spp. All plant species important to white-tailed deer were also important to mule deer. Recruitment to the population was higher for mule deer than for white-tailed deer. Utilization of the annual leader growth on the key browse plant (C. breviflorus) was extremely high. Mule deer were dominant over white-tailed deer in all behavioral interctions observed during the study,. The low. coefficients of distributional overlap and high indices of overlap in food habits for the San Cayetano Mountains indicated that mule deer and white-tailed deer competitvely exclude each other. The high overlap in spatial distributions, habitat selection, and food habits, coupled with the high utilization of the key forage plant (C. breviflorus) in the Dos CabezasMountains during the winter months lead to the conclusion that direct competition between the 2 spp. probably was occurring during that time. This direct competition can be explained on the basis that it is a temporary phenomenon. The factors that have brought mule deer and white-tailed deer into direct competition in this area may have been vegetational changes, livestock overgrazing and/or range fire suppression.

Ecological relationships between mule deer and white-tailed deer in southeastern Arizona USA.

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