Dr. Hoof Stock

Lets dialogue about birthing behavior here…

Hofmann (1988 ) classified grazing ruminants into three basic categories along a continuum. These three categories are 1) the grass-roughage eater, 2) the intermediate feeder, and 3) the concentrate selector. Concentrate selectors are best illustrated by the white-tailed deer, the intermediate feeder by the goat, axis, and fallow deer, and the grass roughage eater by the cow.

The differences in the three categories of ruminants relates chiefly to the [change in] the rumen over evolutionary history. Grass-roughage eaters have the largest rumen relative to body size and have the most highly developed rumen relative to the other types. Because of the more highly developed rumen, grass-roughage eaters may subsist on lower quality diets that are less digestible. Digestibility rates are governed primarily by forage species and stage of maturity of the forage when consumed. Grasses, especially the C4, or warm-season, grasses are typically lower in nutritive value than are the diets selected by the concentrate selector. Concentrate selectors have a smaller rumen relative to body size and the least developed rumen relative to the other types. Concentrate selectors must choose diets that are highly digestible and have short residence times in the rumen. Typical diets include annual forbs and leaves, buds, and twigs or woody plants; these forage items are commonly referred to as browse. Intermediate feeders, as the name suggests, may subsist on either type of forage base.

Waterbuck are described in the literature as grass-roughage eaters. Thus, their forage base of choice will be the introduced (bermudagrass) and native grass species found at Fossil Rim. While the current population of waterbuck at Fossil Rim is low, [one hypothesis is that] exponential growth of the other species at Fossil Rim, in particular fallow deer, is creating increased competition for a decreasing amount of forage resources. [According to this hypothesis, t]he reason resources are decreasing is that woody species encroachment into the grassy meadows at Fossil Rim is reducing the forage base required by the waterbuck at the same time the number of competitors is increasing dramatically.

[If w]aterbuck calf mortality has increased recently [in the newborn age class, o]ne hypothesis for this [possible] increase might be that female waterbuck are not able to maintain adequate body condition during critical lactation periods, thus reducing the ability of the calf to adequately develop and successfully be recruited into the herd. Reduced forage availability could therefore affect either the female during gestation and post-parturition and subsequently impact the calf. An alternative to this hypothesis might be that the calf, post weaning, is unable to obtain adequate nutrition due to the intense competition for the decreasing levels of resources.

From a purely management standpoint, two recommendations would be made. The first would be to immediately implement a woody species management program. While certain levels of ash juniper will be required to maintain golden cheek warbler habitat, open areas must be maintained for the grass-roughage eaters such as the waterbuck. The other recommendation would be to reduce the number of animals at Fossil Rim. The current high population is not sustainable.

Larry

[For more scientific sources on this general topic of herbivore plant interactions, see  Bibliography ]

[editorial changes in brackets by Jane 6/19/08]

Want to help collect natural history data for this inquiry project? This is where we will dialogue about the type of data and the procedures for uploading it to the map on the page “about waterbuck”. We welcome participation by students of all ages, who are interested in experiencing what it is like to actually do scientific inquiry.

Lets keep track here of our peer-reviewed sources of information on natural history:

Skinner, J.D. and Smithers, R. H. N. 1990. Mammals of the Southern African subregion. 2nd Edition. University of Pretoria, Pretoria. South Africa. 793 pp.

Spinage, C.A. 1982. A Territorial Antelope: The Uganda Waterbuck. Academic Press Inc., London, Ltd.
Spinage, C.A. 1986. The natural history of antelopes. Facts on File Publications, New York. 203 pp.

Estes, R. 1991. The Behavior Guide to African Mammals: Including Hoofed Mammals, Carnivores, Primates. University of California Press.

Ryder, O. A. 2000. Genome evolution in Artiodactyla and its relevance to conservation. pp. 296-309 in: E. S. Vrba & G. B. Schaller, eds. Antelopes, deer, and relatives: fossil record, behavioral ecology, systematics, and Conservation. Yale University Press: New Haven. 341 pp. [Evans library QL 737 U5]

Walther, F. R. 1984. Communication and expression in hoofed mammals. Indiana University Press, Bloomington. 423 pp. [Evans library QL737 U4; Biodiversity Stewardship Lab]

Cary Mungall. E. 2007. Exotic animal field guide. Texas A&M University Press, College Station. 286 pp. [Evans library QL737 U4]

RELATED SPECIES
Stanley Price, M. R. 1989. Animal re-introductions: the Arabian oryx in Oman. Cambridge University Press. Cambridge. 291 pp. [Evans library QL737 U53]

Dixon, A. & E. Jones (eds). 1988. Conservation and biology of desert antelopes. The Zoological Society of London, Kent, U.K. 238pp. [Evans library QL737 U53]

For more information on herbivore/forage interactions and the comparative sociality of ungulate species, see Bibliography .