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The detection of chemical alarm cues plays an important role for predator avoidance in many taxonomic groups, but little is known about the presence of such chemical cues in adult or caudate amphibians. We investigated the response (i.e., aversion or nonaversion) to chemical cues from damaged salamander skin and mealworms (Tenebrio molitor) in the plethodontid salamander,Desmognathus ochrophaeus. Avoidance responses were demonstrated to skin extracts of both conspecific and heterospecific salamanders. However, salamanders (D. ochrophaeus) did not avoid heated conspecific skin, fresh conspecific viscera, fresh mealworm, or freshPlethodon richmondi skin extracts. These results indicate that chemical alarm cues are: (1) present in the skin ofDesmognathus salamanders, (2) not present in mealworm or the viscera ofDesmognathus salamanders, and (3) denatured or deactivated by heating. These results also suggest that an avoidance response to chemical cues from damaged conspecifics has adaptive value in predator avoidance in terrestrial as well as aquatic vertebrates.

Many fishes and aquatic invertebrates use chemical alarm cues to avoid predation, however relatively little is known about the occurrence of chemical alarm cues in amphibians. We tested the response of adult fire-bellied newts (Cynops pyrrhogaster) and red-spotted newts (Notophthalmus viridescens) to chemical cues from damaged tissues of newts and other salamanders. Both species avoided chemical cues from a conspecific skin extract. Notophthalmus viridescens also avoided chemical cues from C. pyrrhogaster skin extract, but the converse was not true. Neither species avoided chemical cues from a conspecific viscera extract, plethodontid salamander (Desmognathus and Plethodon) skin extracts, or a conspecific skin extract which had been heated. These results indicate that the avoidance behaviour is an alarm response to chemical cues released from damaged newt skin and is not a general response to chemical cues from damaged salamander tissue. This study provides the best evidence to date for an avoidance response by caudate amphibians to chemical alarm cues.

Competitive interactions among widely sympatric species of terrestrial plethodontid salamanders have received little attention. I investigated whether interspecific interference competition for space occurs between one such pair of species, Plethodon kentucki and P. glutinosus. Encounters between heterospecific adults in the laboratory resulted in aggressive interactions as often as did encounters between conspecific adults. However, intense aggression (bite-holds) occurred more often during pairings between conspecifics, indicating that interference competition is greater among individuals of the same species. Plethodon glutinosus was dominant more often than P. kentucki during encounters with heterospecifics in the laboratory. During a second laboratory experiment, both species preferentially used large cover sites in single-species control groups, whereas P. kentucki used small cover sites significantly more often in mixed-species experimental groups, indicating competitive exclusion of P. kentucki by the larger P. glutinosus. In natural habitats, individuals of both species were usually found alone under cover objects, and the extent of home-range overlap did not differ between conspecifics and heterospecifics. My results indicate that these species compete for space and defend territories against heterospecifics as well as conspecifics. Greater intraspecific than interspecific interference competition may permit coexistence if the former is more important in limiting the population growth of each species.

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