The cleaning ecology of devil rays (Mobula eregoodootenkee) on Monad Shoal, Malapascua Island, Cebu, The Philippines

Supervisor: Dr Simon Oliver (University of Liverpool & Thresher Shark research and Conservation Project)
Video recordings of the pygmy devil ray Mobula eregoodootenkee visiting Monad Shoal seamount in the Philippines were investigated. Almost nothing is known regarding M. eregoodootenkee, and so this may be the first study into their behaviour and ecology. This ray was observed to visit the seamount due to its role as a cleaning station. Cleaner-reef teleost interactions have been investigated by recent authors, however cleaner-ray interactions are virtually unstudied. Nearly 11 hours of video footage was analysed spanning April 2008 – May 2010, with 138 cleaning events taking place. Cleaning interactions took place between 06:00 and 14:30, with the majority of activity occurring before 10:00. Cleaner solicitation (posing) was not a prerequisite for a cleaning event, with 94 cleaning events taking place in absence of any posing behaviour. The length of time that the rays spent at the cleaning station directly correlated to the length of time that they were inspected for. Furthermore, the longer the ray spent posing, the longer the cleaner spent inspecting it. From 500 inspections, 37.6% took place on the rays pelvis, 16.8% on the head, 13% and 12.8% on the left and right pectoral fins, 7.6% on the tail, 5.6% on the stomach, 3.4% on the back and 3.2% on the gills, which shows that cleaners show preferential foraging. Intraspecific and multiple ray cleaning interactions took place, indicating that Monad Shoal is important for a variety of species. Cleaner-ray interactions corresponded with cleaner-reef teleost interactions. Seamounts are viewed as increasingly important for the marine ecosystem as cleaning stations and foraging grounds. Monad Shoal supports cleaning interactions for many pelagic elasmobranchs.