A lever model of jaw action indicates that the maximum bite force of white-lipped peccary (Tayassu pecari) should be at least 1.3 times that of collared peccary (T. taiacu) on food items of a given size. This prediction is consistent with the measured resistances of seeds and nuts that are eaten by the two species at a rain forest site in southeastern Peru. Such a difference in bite force, in association with differences in group size and digging ability, may be a basis for coexistence of the two species in Neotropical rain forests. THERE ARE TWO RECENT SPECIES OF PECCARY native to Neotropical rain forests: white-lipped peccary (Tayassu pecari) and collared peccary (T. tajacu). A third species, the newly discovered Chacoan peccary (Catagonus wagneri), is limited to the dry thorn forests of the South American Chaco (Wetzel et al. 1975; Wetzel 1977a, 1977b). The ranges of both T. tajacu and T. pecart extend southward into somewhat drier regions of South America, including the Chaco (Cabrera and Ypes 1940, Alston 1880, Wetzel 1977a). In the north, only T. tajacu occurs beyond the rain forests, as far as the Sonoran and Chihuahuan deserts of Mexico, Arizona, and Texas (Hall and