Behavioral interactions between salamanders and centipedes: competition in divergent taxa

Red-backed salamanders, Plethodon cinereus, use territorial advertisement in the form of agonistic displays and pheromonal scent marking as a mechanism for intraspecific interference competition. Although ecological and behavioral interactions among species of salamanders have been well studied, little is known about the interactions between territorial P. cinereus and other ecologically similar species, such as large predatory invertebrates. Our field data indicate that P. cinereus and a large syntopic centipede, Scolopocryptops sexspinosus, exhibit negative spatial associations in natural habitats, possibly indicating interspecific territoriality. Only seven instances of salamander/centipede co-occurrence were recorded from a field sample of 247 occupied cover objects. Cover object size was positively correlated with salamander SVL (tip of the snout to the anterior end of the cloaca), but there was no correlation of cover object size to centipede length. Data on the ability of P. cinereus to differentiate among chemicals on the substrate suggest that visual cues are not necessary to elicit a territorial response from intruding salamanders. Although in laboratory trials salamanders behaved similarly toward intruders of both species, biting was directed only toward centipedes. Salamanders spent significantly more time approaching centipedes than they did approaching other salamanders. Approach behavior was often associated with nose tapping and may be an investigative, rather than aggressive, behavior. We suggest that territorial P. cinereus respond similarly to intruding salamanders and centipedes, but that they escalate more readily to biting centipedes because S. sexspinosus is sightless and thus unable to respond to visual signals. Key words: aggression, centipede, Plethodon cinereus, salamander, Scolopocryptops sexspinosus, spatial distribution. [Behav Ecol 15:679–686 (2004)