Abstract: Behavioral interactions between the calanoid copepod Temora turbinata and the ciliates Strobilidium sp. and an undetermined species of spinning ciliate were video-documented and analyzed. Videotaped Temoraciliate encounters were image-analyzed to calculate ciliate swimming trajectories, T. turbinata attack kinematics,
and reaction distances to the ciliates. Wide variances were found in the measured reaction distances. The spinning ciliate was able to sense a copepod from a longer distance and escaped from the feeding current with a faster response than did Strobilidium sp. Our observations suggest that spinning and other evasive behaviors such as jumping are predator-deterrent strategies of ciliates. The copepod could differentiate between living and non-living organisms and ejected non-ingestible particles. Incorporating species-specific interactions from behavioral studies will improve future food web models.