Coconut Husk-Piles-A Unique Habitat for Jamican Terrestrial Frogs

Abstract

Use of coconut husk-piles, a man-made habitat, by two native and two introduced species of terrestrial-breeding frogs was investigated in Jamaica. Introduced species Eleutherodactylus johnstonei and E. planirostris were abundant at drier sites while sympatric endemics E. gossei and E. cundalli were common at sites with higher rainfall. Fewer frogs of all species occurred in husk-piles in the wet season than in the dry season. Sixty-five husk-piles examined contained 0-38 frogs (025/m3) in the wet season and 0-159 frogs (0-58/m3) in the dry season. Population removal of all frogs from test piles in the dry season resulted in rapid reinvasion by introduced species. Frogs did not reinvade vacant piles in wet-season tests. Introduced species are using primarily drier sites which are less hospitable to native species. SUCCESSFUL COLONISTS ON OCEANIC ISLANDS must fit into the established community either by using habitats unsuitable to native species or by displacing natives. A man-made habitat of tropical coastal lowlands, coconut husk-piles, provided an opportunity to investigate the interactions between invading and native species of terrestrial frogs on the West Indian island of Jamaica. With few exceptions, all major habitats on Jamnaica have been altered extensively by man. At elevations below 600 m one of the common man-made habitats is the coconut grove. Plantings vary in size from huge plantations to only a few trees. When coconuts are shelled for harvest, the split, lightweight, fibrous husks are piled around the base of each tree (fig. 1) where they may be left to accumulate. Husks next to the ground decay, producing a fine, loose substrate. The resulting gradient of moisture and interstitial space throughout the husk-pile provides a variety of conditions which supports many organisms, primarily fungi, arthropods, reptiles, and amphibians, notably several species of Eleutherodactylus (Leptodactylidae). Since most Jamaican species of Eleutherodactylus live on or near the ground, they are wellsuited to use such a habitat. We investigated use of the husk-pile habitat bv four species of Eleutherodactylus to determine the degree that terrestrial frogs use such an artificial habitat, relative use by the four species, seasonal use, factors influencing differential use at moist and at dry sites by exotics and by endemics, and the roles these man-made habitats play in successful colonization of Jamaica by two invading species. Population removal experiments were conducted to determine seasonal differences in population pressure on the husk-pile