Well developed, complex rain forests of humid tropical lowlands (RFHTL) do not seem to support large populations of animals compared with other types of forest. Recent studies of terrestrial and understory species of tropical and subtropical forests indicate that the resources available to animals of RFHTL are generally scattered and uncommon. Human populations that utilize this environment contend with a similar pattern of resource availability. On the forest floor only ants and termites, among insects, are consistently common; they are utilized as food by a variety of specialized ground insectivores. Terrestrial herbivores that eat large fallen fruit are also generally scarce as are the often specialized insectivores that seek typically uncommon understory foliage insects, The low densities and high degrees of specialization that accommodate animal species to resources of RFHTL may be ultimately due to a combination of relatively low net primary productivity of undisturbed mature rain forest and the rapid rate of microbial decomposition of forest litter. To develop strategies of conservation suited to RFHTL it will be necessary to understand both the responses of animals to catastrophic disturbances and the often idiosyncratic ways in which animals and people utilize scattered and scarce resources.