Costa Rican range horses break the hard, ripe fruits of Crescentia alata with their incisors and swallow the small seeds imbedded in the sugar-rich fruit pulp. The seeds survive the trip through the horse and germinate in large numbers where horses have defecated. The ripe fruits required about 200 kg pressure to break, and fruits that were too hard for the horses to break required 272 to 553 kg to break. Unbreakable fruits had thicker hulls, and their presence provides an example of how a fruit trait may serve to spread seeds among more than one kind of large dispersal agent. Crescentia alata (Bignoniaceae, 'jicaro') is a common and widespread shrubby tree in the lowland, grassy habitats o,f the Pacific side of Central America. It is native to this area, yet in many places the large, cauliflorous, hard, and indehiscent fruits (fig. la) fall to the ground below the tree, ripen over the next three-five weeks, and rot without ever being touched by a potential dispersal agent. The many small, soft seeds imbedded in the sugar-rich pulp die without germinating in the unopened fruits. This fate is typical even in National Parks containing an apparently normal fauna of large mammals. These observations bring to mind the question of what animal is the normal dispersal agent of C. alata and how does this agent eat such a large fruit? The answer is found in habitats where horses have access to C. alata trees. The brittle, ripe fruits are bitten open by range horses and the black, moist, sweet, and seed-rich contents are swallowed after only slight chewing. Many of the seeds survive the trip through the horse and shortly thereafter germinate in the remains o,f the dung (fig. le). The modern, introduced horse (Equus caballus) is a dispersal agent of C. alata, so, presumably, the Pleistocene horse that undoubtedly occupied C. alata habitats until 10,000 years ago was also (Janzen and Martin 1982). In Santa Rosa National Park, as elsewhere in the semi-forested pastures in the lowlands of Pacific coastal Costa Rica, range horses are avid consumers of the contents of ripe fruits of C. alata. Here I describe in detail how they do it, ask how much effort it requires, and consider the significance of the fruits that are so hard that horses cannot break them.