Dietary overlap among axis, fallow, sika, and white-tailed deer in the edwards plateau region of Texas



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Forage use was determined by microhistological a~alysis from rumen samples collected from 108 axis deer (Axis axis), 92 fallow deer (Dama dama), 82 sika deer (Cer~Js nio~o~), and 101 white-tailed deer (Odocoileus yirginiaous) on 3 replicate study areas in the Edwards Plateau Region of Texas during Winter I, 15 December 1987 to 15 January 1988; Summer I, 15 July to 15 August 1988; Winter II, 15 December 1988 to 15 January 1989; and Summer II, 15 July to 15 August 1989. Selection values were calculated from ranked forage availablity and use data. Dietary overlap was quantified using Kulcynski's coefficient of similarity index. Axis deer consumed a large proportion of grass when it was succulent; however, high forb use and selection occurred when available. Browse use increased substantially during the 2 winters and second summer by axis deer. Therefore, during times of seasonal stress for white-tailed deer, axis increased their dietary overlap and potential competition with whitetails. Fallow deer may potentially compete more with whitetailed deer for highly nutritious forage items than axis and sika, but the detrimental consequences may be as great for fallow as they are for whitetails. Fallow diets contained 40-50% grass, but had the highest forb use and selection of the exotics. Browse use was high and the species used were impor~ant whitetail forages, such as oa~ species. Sika deer appeared to consume forages in near propor~ion to their availability. Sika diets contained abo~t one-half grass and had the lowest use and selection values for forbs. Browse use was high during all collection periods, particularly during the 2 winters. This high browse use and overlap with white-tailed deer may be less detrimental than it appears, for Ashe juniper (a very abundant and low quality forage) contributed a major proportion of this. However, sika are potentially highly competitive with white-tailed deer during times of stress, and if left unmanaged would most likely outcompete whitetails. Similarity values indicated a high degree of overlap among some of the species comparisons, particularly among the exotics. Browse use was high among all species comparisons during the winters and declined somewhat during the summers. Axis and whitetails had the lowest overlap for browse throughout the 4 collection periods. Grass overlap was high among the 3 exotic species during both seasons, but exotic: whitetail comparisons· showed minimal overlap. Forb overlap was typically high for all comparisons. Sika and whitetail had the lowest forb overlap throughout the study. Forage use and selection values for axis, fallow, sika, and white-tailed deer appeared to be unique among each of the ce~vid species. However, there was a relatively high degree of dietary overlap between all species comparisons. Of exotics studied, all exhibited moderate to high dietary overlap with white-tailed deer during the winter and summe~ critical stress periods over the 2 years. All 3 exotics showed the ability to be flexible intermediate feeders, while whitetails were consistently concentrate selectors. Forage availability and quality fluctuations between seasons and years affected each species' diet and the intensity that they potentially competed with other herbivore species. Stringent and proper control of herbivore composition and species densities are paramount in a multispecies grazing system. If white-tailed deer quality and quantity are the major qoals, the simplest and most plausible ranch plan probably would contain only cattle and whitetails; however, if incorporation of exotics is desired, intensive management is needed to ensure an adequate supply of each species most important forages.



Axis (Genus) -- Food, Fallow deer -- Food, Sika deer -- Food, Deer -- Texas -- Edwards Plateau Region