DIET SELECTION IN RODENTS - AN EXPERIMENTAL TEST OF THE EFFECT OF DIETARY FIBER AND TANNINS ON FEEDING-BEHAVIOR

The individual effects of chemical plant defenses on food preferences in small mammals have been explored in many studies. However, the comb ined effects of dietary fiber and tannins on feeding preference have r eceived considerably less attention. Here I search for differences in feeding behavior of alternative experimental diets differing in fiber (cellulose = F) and a secondary metabolite (the hydrolyzable tannin, t annic acid = TA) in two sympatric rodent species that live in the Medi terranean environments of central Chile. I used the herbivorous burrow ing caviomorph rodent Octodon degus (specialist), and the granivorous Sigmodontine Phyllotis darwini (generalist). These species differ in t heir trophic niche, and likely in behavioral and physiological feature s to cope with plant defenses. In preference trials with isocaloric di ets, both species prefered dietary items with low F and TA. I conclude that non-energetic dietary features influence feeding strategies, and that generalist and specialist species behave in the same way. Future studies dealing with the ecology of foraging on chemical plant defens es should focus more explicitly on the interactive effect of different plant defensive compounds instead of on the isolated effect of single factors.