Threat-sensitive predator-avoidance behaviour in the threespine stickleback (Gasterosteus aculeatus) : its development and significance in the larval stage

Bishop, Todd D. (1990) Threat-sensitive predator-avoidance behaviour in the threespine stickleback (Gasterosteus aculeatus) : its development and significance in the larval stage. Masters thesis, Memorial University of Newfoundland.

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Abstract

Threat-sensitive predator-avoidance theory predicts that prey should assess the relative threat posed by a predator and then adjust their behaviour to reflect the magnitude of the threat. This is based on the premise that it is non-adaptive for prey to give up feeding or mating opportunities in the presence of non-threatening predators. In this study, larval threespine sticklebacks were tested for threat sensitivity by exposing them to conspecific predators of various sizes. Larvae were found to display behaviours which suggested threat-sensitivity, such as performing maximum predator-escape responses only to direct attacks and reduced responses to less threatening situations. The onset and disappearance of certain predator-escape behaviours during ontogeny may be related to the development of the dorsal and pelvic spines, along with independence from paternal care. -- Other evidence for threat-sensitivity indicates that larvae exposed to larger predators displayed a reduction in feeding behaviour compared to larvae exposed to small predators or larvae not exposed to predators. This reduction in feeding behaviour may be influenced by the predator/larvae size ratio which indicates an increase in feeding behaviours associated with a decrease in the predator/larvae size ratio. -- Responses of stickleback larvae to active nonspecific and non-active, ambush type predators were compared to test the hypothesis that the larvae would be more vigilant towards an active predator. Neither predator type were found to have significant influences on the behaviours performed by the larvae.

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