Strategies of Seed Dispersal and Seed Predation in Amazonian Ungulates

Abstract

Amazonian ungulates, which include the red brocket deer, grey brocket deer, collared peccary, white-lipped peccary, and lowland tapir, consume large quantities of fruit and maximize nutritional gain by exploiting both pulp and seed. Amazonian ungulates often disperse seeds over short distances by spitting them out during mastication. The lowland tapir is the only ungulate that frequently disperses intact seeds through the digestive tract. Brocket deer destroy most of the seeds they consume by digesting them with rumen microbes, while peccaries crack seeds using their resistant teeth, strong jaw musdes, and thick skull bones. Defensive strategies of seeds include strength, chemical toxins, mast fruiting, fibrous lignin, and size variation. Brocket deer and peccaries have pregastric fermentation that may detoxify some secondary compounds of seeds. Small seeds occasionally pass intact through brocket deer and peccary guts. However, strong palm seeds that avert many mammalian predators are often destroyed by ungulates. The fibrous lignin that protects seeds of Jessenia bataua (Palmae) appears to be effective against ungulates which may explain its abundance in the study area. AMAZONIAN UNGULATES CONSUME large quantities of fruit. Fruit constitutes 81 percent of the diet of red brocket deer (Mazama americana), 87 percent of grey brocket deer (M. gouazoubira), 59 percent of collared peccary (Tayassu tajacu), 66 percent of white-lipped peccary (T. pecarn) (Bodmer 1989) and 33 percent of lowland tapir (Tapirus terrestnis) (Bodmer 1990a). Much of the fruit consumed by these large-bodied terrestrial herbivores consists of residual fruit production (those fruits not consumed by arboreal animals that reach the forest floor) and to a lesser extent fruits of subcanopy plants. Therefore, ungulates do not have access to the full range of fruits which are available to arboreal frugivores, such as primates, fruit bats, and birds (Eisenberg & McKay 1974). Plants produce pulpy fruits to attract animal vectors, which, in turn, disperse seeds. Seeds are protected against predators by physical characteristics such as hardness or spines, chemical toxins, and saturation strategies via mast fruiting (Janzen 1971, Waller 1979, Kiltie 1982, Bell 1984, Dirzo & Dominguez 1986). However, ungulates maximize nutritional intake from forest fruits by exploiting the entire fruit resource, including protected seeds (Kiltie 1981, Smythe 1986). This paper examines the extent of seed dispersal and seed predation in Amnazonian ungulates, the various ways in which ungulates disperse seeds, and their adaptations for seed predation. The paper also examines the various ways seeds protect themselves from predators and how brocket deer, peccaries, and tapir overcome these seed defenses.