Functional Response of Herbivores in Food‐Concentrated Patches: Tests of a Mechanistic Model

• DOI: 10.2307/1940805
• Publication Date: 2006-05-09T15:13:26Z
• Authors: John E. Gross; Lisa A. Shipley; N. Thompson Hobbs; Donald E. Spalinger; Bruce A. Wunder
• Keywords: Optimal foraging theory

Type II functional responses are frequently observed in herbivores feeding patches where plants concentrated space. We tested a mechanistic model of regulation intake rate foraging food—concentration (Laca and Demment 1992, Spalinger Hobbs 1992) that accounts for asymptotic, responses. The is based on the hypothesis competition between cropping chewing regulates instataneous response to changes size bites obtained by forager. this examined ability our account observations 12 species mammalian ranging body mass over 4 orders magnitude. measured short—term rates hand—assembled plants. varied bite changing plant height density offered herbivores, dry matter variation. Averaged across species, accounted 77% variance food (P <.001 all species). Predictions maximum closely resembled processing capacity, demonstrating rather than sets an upper limit intake. Tests mechanisms provided strong support responsible seen patches. was able consistently predict 16 previous studies. These results indicate characteristics regulating (e.g., leaf geometry, spinescen) control instantaneous herbivores.