My research centers on the ecology and behavior of tropical anurans, both adults and larvae. I am especially interested in underlying mechanisms that determine the number and abundance, i.e., structure, of amphibian communities in tropical habitats. I have worked with small communities that occur in phytotelmata such as Brazil nut fruit capsules and larger assemblages of small frogs and lizards that occur in leaf litter habitats. In the Brazilian Amazon region, Brazil nut capsules are breeding sites for two species of frogs, a dendrobatid and a bufonid. Both species must interact with predaceous insect larvae that occur in the same microhabitat, including larvae of giant damselflies in the Family Pseudostigmatidae and mosquitoes in the genus Toxorhynchites. My work has revealed that the two species of anurans utilizing this microhabitat have different strategies for offsetting predation by these two insect larvae. As an outgrowth of this work, I have become interested in aspects of the biology of tadpoles in the Dendrobates clade. These tadpoles are unusual because they develop in small phytotelm microhabitats; they are predaceous and, under certain conditions, cannibalistic.

In 1996, I worked on social behavior of Dendrobates vanzolinii, a small frog that occurs in western Acre, Brazil. Males and females of this species form pair bonds and cooperate to feed nutritive (unfertilized) eggs to their tadpoles, which are deposited singly in tiny phytotelmata (usually holes in vines) in the rainforest.

Another area of research is the partitioning of food resources and its role in determining community structure. Relatively little is known about whether ontogenetic changes occur in diets of anurans and what the nature of the shifts, if they occur, might be. At certain seasons, juvenile frogs can be very abundant. Whether prey availability or actual changes in preference affect ontogenetic shifts are unknown for most frogs. Some small frogs specialize on mites, for example, and the diet consequences of eating mites, ants, and other chitinous insects are unknown. I am especially interested in the evolution of diets of poison frogs in the Family Dendrobatidae and how diet is related to skin toxins.

Recently, many herpetologists have become concerned about the rapid decline and disappearance of certain populations and species of amphibians around the world. Many of the declines are associated with habitat destruction, especially the loss of tropical rain forest, but other declines have occurred in relatively pristine areas. I am interested in the influence of disturbance in tropical forests on population size and distribution of amphibians. For example, it appears that roads leading into tropical forests are providing corridors of dispersal for certain amphibians that would otherwise be rare in undisturbed forest. I have worked in an area in eastern Brazil where selective logging of tropical rainforest was carried out; in this area, small logging roads through the forest appear to be increasing breeding sites for amphibians because of the formation of pools of water in these roads.

• Cooper, W. E., Jr., Pérez-Mellado, V., Baird, T. A., Caldwell, J. P., and Vitt, L. J. 2004. Pursuit deterrent signaling by the Bonaire whiptail lizard, Cnemidophorus murinus. Behaviour 141:297-311.

• Baird, T. A., Vitt, L. J., Baird, T. D., Cooper, W. E., Jr., Caldwell, J. P., and Pérez-Mellado, V. 2004. Social behavior and sexual dimorphism in the Bonaire whiptail, Cnemidophorus murinus (Squamata: Teiidae): The role of sexual selection. Canadian Journal of Biology 81:1781-1790.

• Caldwell, J. P., and Araújo, M. C. 2004. Historical and ecological factors influence survivorship in two clades of phytotelm-breeding frogs (Anura: Bufonidae, Dendrobatidae). In: Ecology and Evolution of Phytotelm Breeding Anurans. R.M. Lehtinen (ed.). Miscellaneous Publications, Museum of Biology, University of Michigan 193:11-21.

• Vitt, L. J., Caldwell, J. P., Sartorius, S. S., Cooper, W. E., Jr., Baird, T. A., Baird, T. D., and Pérez-Mellado, V. Pushing the edge: Extended activity as an alternative to risky body temperatures in an herbivorous teiid lizard (Cnemidophorus murinus: Squamata). In Press, Functional Ecology.

• Lima, A. P., Caldwell, J. P., and Biavati, G. M. 2002. Territorial and reproductive behavior of an Amazonian dendrobatid frog, Colostethus caeruleodactylus. Copeia 2002:44-51.

• Caldwell, J. P., Lima, A. P., and Keller, C. 2002. Redescription of Colostethus marchesianus (Melin, 1941) from its type locality. Copeia 2002:157-165.

• Caldwell, J. P., Lima, A. P., and Biavati, G. M. 2002. Descriptions of tadpoles of Colostethus marchesianus and Colostethus caeruleodactylus (Anura: Dendrobatidae) from their type localities. Copeia 2002:166-172.

• Caldwell, J. P., and Lima, A. P. 2003. A new Amazonian species of Colostethus with a nidicolous tadpole.Herpetologica 59:218-233.

• Cooper, W. E., Perez-Mellado, V., Baird, T. D., Baird, T. A., Caldwell, J. P., and Vitt, L. J. 2003. Effects of risk, cost, and their interaction on optimal escape by nonrefuging Bonaire whiptail lizards, Cnemidophorus murinus.Behavioral Ecology 14:000-000.

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