ONTOGENIC CHANGES IN CALIFORNIA NEWTS (TARICHA-TOROSA) IN RESPONSE TOCHEMICAL CUES FROM CONSPECIFIC PREDATORS

Many species of aquatic animals rely on chemical cues to assess the ri sk of predation. Although amphibians are known to have adaptations to avoid predatory fish, little is known about their adaptations that all ow them to co-occur with other aquatic vertebrate and invertebrate pre dators. Adult California newts (Taricha torosa) prey on egg masses and larvae of conspecifics. Larvae use chemical cues to assess the risk o f cannibalism. Laboratory studies showed that larvae that are two week s post-hatching hid in response to chemical cues from adults. Larvae f ive weeks post-hatching did not respond to conspecific cues regardless of previous exposure to adult cues. Field surveys supported the predi ction that small larvae would use refuges more than larvae that are on ly slightly older. Surveys of natural stream pools showed that newt la rvae spent more time in refuge early in the summer than they did later in the summer. This behavioral shift also corresponds to the time of year when adults leave the streams and return to land. Thus, newt larv ae showed an abrupt ontogenetic change in their response to conspecifi c chemical cues. Reduced sensitivity to conspecific risk suggests that large newt larvae are less vulnerable to conspecific adults than smal l larvae.