Lizard ecology in the canopy of an island rain forest

TitleLizard ecology in the canopy of an island rain forest
Publication TypeBook Chapter
Year of Publication1995
AuthorsReagan, PD
EditorLowman, MD, Nadkarni, NM
Book TitleForest canopies
PublisherAcademic Press, Inc.
CityOrlando, Florida
Accession NumberLUQ.516
Keywordscanopy, community, invertebrates, tropical forest

Information on animals in rain forest canopies consists almost exclusively of data on mammals and birds(Odum and Pigeon, 1970; Whitmore, 1975; Janzen, 1983; Leigh et al., 1985). Although amphibians, such as Wallace's flying frog (Rhacophorus nigropalmatus) and reptiles such as the paradise tree snake (Chrysopelea pelias) and flying dragon (Draco volans) are known to inhabit the upper parts of tropical rain forest, data on their own populations in the canopy are sparse. The primary reasons for this are the difficulties in observing amphibians and reptiles (which are generally small and relatively immobile) more than a few meterabove ground level, and the challenges of conducting studies within the forest canopy.
The anoline lizards (Anolis spp.) are the most abundant and conspicuous vertebrates that inhabit the terrestial ecosystems on islands in the Caribbean (Moermond, 1979; Williams 1969, 1983). On large islands several species occur syntopically in forest habitas and partition the habitat vertically (Williams, 1972). The habitat and vertical distribution of anoles in Puerto Rico have been investigated by ground-based observers (Rand, 1964; Schoener and Schoener, 1971; Moll, 1978; Lister, 1981), who documented the presence of anoles in the upper reaches of the forest, but provided few insights on their abundance or possible roles in the animal community of the forest canopy. Recent studies in Puerto Rico have produced quantitive information on the abundance and foraging of the anoline lizard that shows that at least in some rain forest, lizards play a significant role in the animal community of the forest canopy.
My work on canopy lizards began as the result of serendipitous observations made shortly after moving to Puerto Rico in 1979/. I had a accepted a position at the Center of Energy and Environment Research of the University of Puerto Rico and made walking surveys through the forest near El Verde Field Station. On such visit, I climbed to the top of a tower that had been erected during the 1960s for irradiation studies. Looking out through the canopy, I noticed several Anolis stratulus on the uppermost branches of nearby trees. Because i could see several individuals from a single point, I reasoned that they must be abundant and, therefore, it might be possible to study them from the tower. This chance of observation of anoles in the canopy led me to investigate the distribution and abundance of A. stratulus and other anole species in three-dimensional habitat of the forest canopy. I began my research with vertical transects to document the vertical distribution and general abundance of anole species in the forest. The results of this study raised additional questions on population density, habitat use and the role of A. stratulus in the forest food web, and started me on a course of research in the forest canopy that I have continued to pursue.
My objective in this chapter is to summarize what is known about anoline lizards that inhabit the canopy of rain forests in Puerto Rico and suggest directions for future research of canopy reptiles. Some of the insights have extended our knowledge of ecosystem structure and function in unexpected directions. The role of the anoles in the forest canopies is not yet known; however, the importance of these lizards in the Puerto Rican rain forest canopies is now established.