Abstract

At the individual level, prey are faced with a series of trade-offs between the benefits of predator avoidance and those of a suite of other behaviour patterns. The threat-sensitivity hypothesis, however, assumes that the antipredator behavioural responses shown by prey are graded in intensity in a manner that corresponds with the level of perceived risk. Previous studies examining threat sensitive responses to chemical alarm cues have provided mixed results at best. The first experiment of this thesis examined the influence of subthreshold chemical cues on the threat sensitive decision of foraging posture. Juvenile convict cichlids ( Archocentrus nigrofasciatus ) were given a choice of head-down or head-up foraging posture, and exposed to sub-threshold or suprathreshold alarm cues. Cichlids exposed to the subthreshold cue did not exhibit an overt antipredator response, but did significantly alter their foraging posture. Likewise, cichlids exposed to the odour of a piscivorous predator exhibited a similar threat-sensitive shift in foraging posture. The second experiment examined the influence of temporal variation in predation risk on antipredator and foraging behaviour. Convict cichlids were exposed to one of four conditioning regimes, differing in concentration and frequency of alarm cue, and subsequently exposed to conspecific alarm cue or a control. Cichlids initially conditioned to high frequency cues, regardless of cue concentration, increased foraging effort during 'safe' periods and exhibited reduced antipredator responses during 'risky' periods. Together, these results suggest that juvenile cichlids do not respond to chemical cues with the quantitatively graded responses assumed by the threat-sensitivity hypothesis, but rather exhibit threat-sensitivity by making qualitative changes in antipredator and foraging behaviour.