Food Choices by Mammalian Herbivores and the Role of Defense Compounds: Example Beaver
Herbivores such as deer, bovids, rodents, or marsupials encounter a great diversity of plant secondary metabolites (PSMs). These PSMs greatly affect the food choices these animals make. In turn, herbivores affect plants by stimulating induced defenses as a consequence of browsing. For food choice experiments in the wild we need animals that can be found predictably in certain places at certain times. The beaver (Castor canadensis or C. fiber) is such a species. Beavers stay year-round near their lodges and readily accept food provisions.
The beaver is a generalist herbivore. Depending on the local vegetation, many plant species can be beaver’s food. These include a large variety of trees, shrubs, grasses, forbs, and aquatic plants. Beavers select food according to palatability. Nutrient content and aversive plant chemicals determine palatability. Moreover, after beavers or other herbivores have clipped or cut shrubs and trees, the following season’s regrowth will increase its chemical defenses. The new shoots assume the juvenile growth form: compared to adult type growth they have larger leaves, unbranched growth, and intensified chemical defenses. In many areas you will most likely see young saplings of the juvenile growth form in aspen, cottonwood, willow, and basswood.
When beavers first colonize a site they begin by harvesting the most palatable species, such as aspen (Populus spp.) or willow (Salix spp.). Over time, they change the vegetation by their selection of trees for food and construction of dams and lodges. Eventually, often only the least preferred conifers are left, and the beavers move to a new area until some of the depleted vegetation has regenerated. Beavers move back in, and the cycle repeats.
KeywordsGallic Acid Food Choice Black Locust Generalist Herbivore Beaver Pond
- Abu-Zaid MM, Grant GG, Helson BV, Benninger CW, DeGroot P (2000) Phenolics from deciduous leaves and coniferous needles as sources of novel agents for lepidopteran forest pests. In: Shahidi F, Ho C-T (eds) Phytochemicals and phytopharmaceuticals. AOCS, Champaign, IL, pp 398–416Google Scholar