Ram filter-feeding and nocturnal feeding of whale sharks (Rhincodon typus) at Ningaloo Reef, Western Australia

The paper reports feeding behaviours of whale sharks (Rhincodon typus) at Ningaloo Reef, Western Australia that have been observed during field trips over a period of 23 years. Two distinct feeding behaviours have been observed, namely passive feeding, which resembles the ram filter-feeding of the basking shark (Cetorhinus maximus), and active feeding at the surface, as previously described in the literature. Nocturnal surface feeding behaviour is reported. The targeted prey species were specific to the different feeding techniques and times. Contrary to previous reports, the gills of the shark moved actively in a rhythmical fashion during both of the observed feeding modes. The principal prey species identified at Ningaloo have been the euphausiid Pseudeuphausia latifrons, portuniid megalopa, stomatopod larvae, copepods, chaetognatha, and schools of small fish. The diurnal appearance of whale sharks at the surface and the passive feeding witnessed during daylight hours, suggests that the whale shark is searching for localised aggregations of plankton that persist at the surface in the weeks following the reef spawning.