SHELL STRENGTH AND PRIMATE SEED PREDATION OF NONTOXIC SPECIES IN EASTERN AND SOUTHERN AFRICA

The large African primates that eat fruit destroy the seeds of a numbe r of fruiting species. This paper addresses several questions about se ed-eating. What is the nature of the dietary niche provided by the non poisonous seeds of eastern and southern Africa? How well are these see ds mechanically protected? What other means of reducing seed predation are employed by the plants? and is the niche ecologically stable? Mea surements of seed shell strength on 3 7 species from 17 families revea l a range of values, from <100-kg (numerous species) to over 2000-kg ( palm nuts) breaking load. Primates crack open with their teeth seed sh ells from species exhibiting test strengths less than 600 kg. Variatio n in shell strength appears to increase dramatically for average speci es strengths above 100 kg. Plant species are not characterized by spec ific shell strengths but instead, display envelopes of shell strength overlapping broadly with other species. Taking this into account, adul t male baboons (Papio spp.) appear to be dentally capable of preying u pon most of the seed species of eastern and southern Africa. The possi bility for predation of nonpoisonous seeds exists primarily because th e plants periodically produce large crops in synchrony and the hard-sh elled seeds are effectively dispersed, sometimes explosively but more often by means of edible fruits. The concomitant primate seed predatio n is a facultative specialization, of little apparent threat to the co mmunity of plants that support it.