Search

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2006.09.005 Byline: Antoine O.H.C. Leduc, Ellie Roh, Cindy Breau, Grant E. Brown Abstract: The ability to learn context-specific information regarding local predation risk is of prime importance for prey individuals balancing the conflicting demands of predator avoidance with other fitness-enhancing activities. Many taxonomically diverse prey species must learn to recognize novel predators and make context-appropriate responses. Predator-recognition learning in freshwater prey fish is commonly facilitated through the association of a novel predator cue with a damage-released chemical alarm cue. While a multitude of laboratory studies have demonstrated the sophistication of chemically mediated predator-recognition learning, no field verifications of this mechanism have been conducted. We conducted an experiment to determine whether the single pairing of a novel odour (lemon essence) with a damage-released chemical alarm cue could function to facilitate learning in wild juvenile Atlantic salmon under fully natural conditions. Tagged juvenile salmon were initially exposed to either a paired stimulus of conspecific alarm cue and lemon odour or a control of stream water and lemon odour. As predicted, salmon exposed to the alarm cue during the conditioning trials showed a significant increase in antipredator response. When salmon were subsequently exposed to lemon odour alone, only those initially exposed to the alarm cue paired with the lemon odour showed a significant increase in alarm response. Those initially exposed to the stream water and lemon odour control did not show any change in behaviour (i.e. did not learn). As such, these data demonstrate that chemically mediated, acquired predator recognition can occur under fully natural conditions. Author Affiliation: (a) Department of Biology, Concordia University, Canada (a ) Department of Biology, University of New Brunswick, Canada Article History: Received 10 March 2006; Revised 11 April 2006; Accepted 11 September 2006 Article Note: (miscellaneous) MS. number: A10386R

Abstract: Many prey fishes rely on damage-released chemical alarm cues to detect and avoid predators. The ability to use these cues has been shown to confer considerable survival benefits to [...]

Abstract: The threat-sensitive predator avoidance model predicts that prey should balance the intensity of antipredator responses against perceived predation risk, resulting in a graded response pattern. Recent studies have demonstrated [...]

Even at sublethal concentrations, various anthropogenic pollutants may disrupt the transfer of chemosensory information, often inducing maladaptive behavioral responses. Recent studies of freshwater prey fishes have shown impaired abilities to respond to damage-released chemical alarm cues from conspecifics under weakly acidic conditions (pH ∼ 6.0). Several factors acting individually or collectively may account for such chemosensory impairment. By itself, acidification may chemically disrupt the alarm cues and affect fish olfactory functions. Alternatively, differences in local environmental conditions may affect biochemical composition, quantity of chemical alarm cues produced by epidermal tissue, or both, leading to variations in alarm response. Our goal was to assess whether the ability to produce and detect conspecific chemical alarm cues is similar in individuals reared under neutral versus acidic conditions. We conducted two experiments in which we measured the behavioral response of wild juvenile Atlantic salmon exposed to chemical alarm cues. In particular, we looked for differences in the ability of individual fish to (1) produce alarm cues capable of eliciting consistent antipredator behavior in conspecifics and (2) detect alarm cues upon the fish's introduction into a stream with a pH differing from that of the stream of origin; the latter experiment involved reciprocal transplant of fish between neutral (pH range ∼ 7.0-7.3) and acidic (pH range ∼ 5.9-6.3) sites. Our results demonstrate that the ability to produce and respond to chemical alarm cues is maintained in Atlantic salmon reared under acidic conditions and did not differ from that of fish reared under neutral conditions. Overall, these data suggest that no permanent olfactory damage occurred under reduced pH and, likewise, no significant difference in functional alarm cue production existed between Atlantic salmon reared under neutral and acidic conditions. Short-term reduction in olfactory sensitivity and degradation of the chemical alarm cues under acidic conditions are the likely mechanisms affecting detection of these important chemicals by prey fish. [ABSTRACT FROM AUTHOR]

Many organisms rely on chemosensory cues to mediate predation risks. Recent studies have demonstrated impaired chemosensory detection ability under weak acidification. Because rainfall may lead to episodic acidification of surface water, we assessed the effects of acid rain on chemosensory alarm functions. Under natural conditions, we quantified alarm behaviour of juvenile Atlantic salmon (Salmo salar) exposed to conspecific chemical alarm cues before and following rainfall. Before rainfall, salmon were capable of an alarm response in the study streams. After rainfall, salmon from Devil's Brook did not respond to the alarm cues whereas the detection of salmon from Catamaran Brook (a comparable stream having higher acid neutralising capacity) was maintained. To relate these findings to predator–prey encounters, we performed a second experiment where we staged encounters between prey (rainbow trout, Oncorhynchus mykiss) and predator (largemouth bass, Micropterus salmoides) exposed to acidified and unacidified rainbow trout chemical alarm cues. Trout exposed to acidified alarm cues survived for a significantly shorter amount of time than trout exposed to unacidified alarm cues, whereas no difference in overall predator behaviour was observed. Our results suggest that episodic acidification in small nursery streams may disrupt the chemical information mediated by the chemical alarm cues that can translate into higher survival costs for prey. [ABSTRACT FROM AUTHOR]