There may be ways to enhance the information obtained from conventional approaches to examining food habits. Fecal samples are still the most convenient, nonintrusive method to examine food habits of vertebrates. Methods are currently available and others are being developed that may increase the infor mation obtained from such samples. Steroid concentrations (especially estrogen) have been used to examine pregnancy rates among free-ranging mammals (Kirkpatrick et al. 1990). This technique could be modified to distinguish male- and female-derived fecal samples. Even greater sample resolution is possible by using emerging molecular techniques. As indicated earlier, fecal samples contain epithelial cells shed from the intestine walls of the animal depositing the sample. DNA extracted from these cells has been used to identify the species that deposited the sample. Recently, several investigators have used this approach to identify sex and individual genetic markers (Kohn and Wayne 1997; Reed et al. 1997). Therefore, it is possible to substantially increase the resolution of fecal samples so that researchers can track the diet of identified free-ranging individuals. The information obtained from fecal samples could be enhanced even more by using digestibility correction factors that estimate biomass consumed. The resulting data set would probably prove very useful in evaluating diet selection and effects of consumption patterns on the forage or prey community.
As should be apparent by now, substantial information on food use patterns of vertebrates has been collected. Yet the ability of biologists to apply this information to understand factors that affect an organism's fitness or role in community structure has been limited. Perhaps the most needed change is to ensure that future investigations have a more complete context associated with them. Rather than partitioning studies into separate efforts to examine food and habitat use, these investigations should occur (and be reported) simultaneously.
Recent advances in molecular biology will enable vertebrate ecologists to generate a more complete picture of food use patterns by specific segments of a population. Such detailed information will enhance our ability to understand community relationships and spatialemporal patterns of vertebrate abundance. Rather than addressing general questions on the natural history of a specific species or population, clearly defined investigations of animal food habits may enhance our ability to answer the important how and why questions of vertebrate ecology.
Ackerman, B. B., F. G. Lindzey, and T. P. Hemker. 1984. Cougar food habits in southern
Utah. Journal of Wildlife Management 48: 147-155. Adorjan, A. A. and G. B. Kolenosky. 1969. A manual for the identification of hairs of selected
Ontario mammals. Ontario Department of Lands and Forests, Research Report
Alverson, W. S., D. M. Waller, and S. L. Solheim. 1988. Forests too deer: Effects in northern Wisconsin. Conservation Biology 2: 348—358.
Anthony, R. G. and N. S. Smith. 1974. Comparison of rumen and fecal analysis to describe deer diets. Journal of Wildlife Management 38: 535—540.
Barbour, M. S. and J. A. Litvaitis. 1993. Niche dimensions of New England cottontails in relation to habitat patch size. Oecologia 95: 321—327.
Basile, J. V. and S. S. Hutchings. 1966. Twig diameter-length-weight relationships of bit-terbrush. Journal of Range Management 19: 34-38.
Bazley, D. R. and R. L. Jefferies. 1986. Changes in composition and standing crop of salt marsh communities in response to removal of a grazer. Journal of Ecology 74: 693706.
Begon, M., J. L. Harper, and C. R. Townsend. 1996. Ecology. Cambridge, Mass.: Blackwell.
Beier, P. and J. E. Drennan. 1997. Forest structure and prey abundance in foraging areas of northern goshawks. Ecological Applications 7: 564-571.
Bielefeldt, J., R. N. Rosenfield, and J. M. Papp. 1992. Unfounded assumptions about the diet of the Cooper's hawk. Condor 94: 427-436.
Bobek, B., S. Borowski, and R. Dzieciolowski. 1975. Browse supply in various forest ecosystems. Polish Ecological Studies 1: 17-32.
Boutin, S. 1990. Food supplementation experiments with terrestrial vertebrates: patterns, problems, and the future. Canadian Journal of Zoology 69: 203-220.
Brander, T. A., R. O. Peterson, and K. L. Risenhoover. 1990. Balsam fir on Isle Royale: Effects of moose herbivory and population density. Ecology 71: 155-164.
Brown, A. L. and J. A. Litvaitis. 1995. Habitat features associated with predation of New England cottontails: What scale is appropriate? Canadian Journal of Zoology 73: 10051011.
Brown, J. H. and E. J. Heske. 1990. Control of a desert-grassland transition by a keystone rodent guild. Science 250: 1705-1707.
Bryant, J. P. 1981. Phytochemical deterrence of snowshoe hare browsing by adventitious shoots of four Alaskan trees. Science 213: 889-890.
Bryant, J. P., R. K. Swihart, P. B. Reichardt, and L. Newton. 1994. Biogeography of woody plant chemical defense against snowshoe hare browsing: Comparison of Alaska and eastern North America. Oikos 70: 385-395.
Charnov, E. 1976. Optimal foraging, the marginal value theorem. Theoretical Population Biology 9: 129-136.
Chisholm, B. S. and H. P. Schwarcz. 1982. Stable-carbon isotope ratios as a measure of marine versus terrestrial protein in ancient diets. Science 216: 1131-1132.
Ciucci, P., L. Boitani, E. Raganella Pelliccioni, M. Rocco, and I. Guy. 1996. A comparison of scat-analysis methods to assess the diet of the wolf Canis lupus. Wildlife Biology 2:
Was this article helpful?