Accrued reproductive assets in Trinidadian guppies may affect both the costs and benefits associated with anti-predator behaviour and may influence their threat sensitive response pattern. While the threat sensitive behaviour in Trinidadian guppies has received considerable attention, the influence of reproductive assets on threat sensitive response patterns has received little attention. This study compares anti- predator behaviour in gravid (high accrued assets) vs. non-gravid (low accrued assets) guppies from both high and low predation risk populations. A significant difference in anti-predator response was found between gravid and non-gravid guppies in the Lower Aripo population (high predation site); gravid guppies exhibited a stronger overall anti-predator response to the same level of ambient predation threat, whilst non-gravid guppies showed weaker responses. However, in the Upper Aripo population (low predation site), a similar response was found in gravid and non-gravid guppies. The greater anti-predator response observed by gravid guppies in the Lower Aripo population supports the hypothesis that accrued reproductive assets influence threat sensitive response in Trinidadian guppies. Furthermore, the difference in response observed between the Lower and Upper Aripo guppy populations suggests
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that long-term predation plays an important role in shaping anti-predator responses to predation risk. This experiment suggests that gravid guppies from high predation sites integrate accumulated reproductive assets, immediate predation risk and long-term predation pressure to make decisions regarding their anti-predator responses.