Pelagic sharks are poorly understood because of limitations inherent in studying
chem in situ. Knowledge that pelagic thresher sharks (Alopias pelagicus) regularly
visit specific locations in the Philippines presented an unique opportunity to study new aspects of their behaviour and biology, and promote their conservation in the region. Post-mortem examinations were conducted on 11 dead A. pelagicus specimens to investigate their ontogenic growth trends, and ectoparasice attachments. Remote and handheld video was used to directly observe pelagic thresher sharks in situ at two sites in the central Visayas. From 239 video observations of pelagic thresher sharks, I 17 behaviour events were analysed. IO I individual A. pelagicus were identified by using allometry co non invasively assess shark maturity from video still images, and by tabulating physical characteristics that were unique to each shark. Parasite infestation was a proximate cause for pelagic thresher sharks visiting cleaning stations. A. pelagicus adapted their behaviour in a pose to solicit and facilitate interactions with cleaners that provided them with parasite removal services essential to their health and hygiene. Cleaners foraged selectively on pelagic thresher sharks and fed preferentially on specific eccoparasites that occupied specific sites of a shark's body. Evidence from the video records confirmed prior speculations that A. pelagicus hunt with their tails. Pelagic thresher sharks used tail-slaps to stun and kill shoaling sardines. The strategy was efficient since A. pelagicus were able to consume more than one prey fish at a time.
Understanding new aspects of the behaviour and biology of pelagic thresher sharks led to their legal protection in many parts of the Philippines, and provided insight into managing tourism activities at sites where they forage and clean. Observable behaviours seen at these sites may explain why these mainly oceanic sharks venture into shallow coastal waters where they are vulnerable to anthropogenic disturbance.