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Food requirements of wild animals: predictive equations for free-living mammals, reptiles, and birds.


Feeding rates (intake of both dry matter and fresh matter) by 79 species of mammals, 95 species of birds and 55 species of reptiles were estimated from doubly labeled water-based measurements of field metabolic rate on each species (Table 1). Allometric (scaling) regression analyses of log10-transformed feeding rates vs. body mass yielded statistically significant relationships for 90 different taxonomic, dietary and habitat groupings of species. The resulting exponential equations can be used to predict the daily food requirements needed to maintain energy balance for free-living mammals (Table 2), birds (Table 3), and reptiles (Table 4) with an average error of about 5% to 60%, depending on the group. The ability to predict feeding rates of terrestrial vertebrates should be useful to zoo keepers, animal nutritionists, veterinarians, pet hobbyists, wildlife zoologists, game managers, range biologists, preserve directors and planners, conservationists, paleontologists and ecosystem modelers. These equations should underestimate somewhat the feeding rates of free-living animals that are growing, reproducing or storing up fat. The equations probably overestimate the feeding rates of captive wild animals (e.g. in zoos) and of free-ranging animals during some phases of their lives when they either do not or cannot feed normally.

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