Food Chain Length

Early analyses indicated that the length of food chains within food webs should be relatively short, at most 3-5 links (May 1983, Pimm and Kitching 1987, Pimm and Lawton 1977), because the laws of thermodynamics predict energy limitation at higher trophic levels. Therefore, energy gain should be maximized by feeding lower on the food chain. At the same time, competition for prey is most severe at lower levels, perhaps restricting energy gains. Consequently, the trophic level selected by predators represents a tradeoff between maximizing energy availability and minimizing competition. However, Polis (1991b) and Reagan et al. (1996) found chain lengths of 6-19 links using food webs with greater resolution in arthropod taxonomy. Reagan et al. (1996) reported a mean chain length of 8.6, double the length of chains found when arthropods are combined into a single category.

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