Cleaning Station Behavior
Both species of manta ray are known to pay frequent visits to reef cleaning stations. A cleaning station is a specific section of reef that is home to a number of reef-dwelling cleaner fish, who literally clean large marine animals such as sharks, rays and larger bony fish. They do so by eating the parasites, dead skin, bacteria and mucus off of the body surface and gills of the larger fish, as well as from the inside of their mouth. This cleaning process is an example of mutualistic symbiosis, meaning that both parties (the manta ray and the cleaner fish) benefit from the interaction. Cleaning helps to maintain the health of manta rays; cleaner fish remove any ectoparasites living on the skin and clean dead or infected skin from wounds, aiding the healing process and helping to prevent infection. Simultaneously, the cleaner fish are provided with a regular and easily accessible source of food.
A wide variety of fish species display cleaning behavior. The best known are the cleaner wrasses of the genus Labroides, which are found on coral reefs in the Indian and Pacific Oceans; other cleaner fish include species of butterflyfish, damselfish, gobies, wrasse and angelfish. Our studies have shown that in order to avoid competition, different species specialise in cleaning different sections of a manta rays body. For example, Klein’s butterfly fish (Chaetodon Kleinii) specialise in cleaning any bite wounds that a manta may have, whereas cleaner wrasse (Labroides dimidiatus and Labroides bicolor) attend to inside the mouth and around the gills, and moon wrasse (Thalassoma lunare) specialise in picking off calagid copepods from the mantas’ ventral surface.
Manta rays exhibit specific behaviors during visits to cleaning stations. As they approach, they typically reduce their swimming speed, and whilst within the area of the cleaning station may hover almost motionless, or swim in very slow circular patterns over the reef. Their mouths tend to remain slightly open, with the gill slits flared and cephalic fins unfurled, allowing these areas to be attended to by host cleaner fish. It is this specific posture that advertises the manta rays willingness to be cleaned. Mantas usually make consecutive passes over a cleaning station, by circling slowly around the reef and re-approaching from their initial entry point.
Manta rays have been observed to spend extended periods of time at a cleaning station. Our studies in Mozambique have found that on average a manta ray will spend almost 2 hours per day being cleaned, with some individuals spending up to 8 hours in a single day. This is presumably due to increased parasite loads or extent of skin infections or injuries. Individuals will return on consecutive days to the same cleaning stations, especially if they have fresh or healing wounds. Manta rays display what is known as site fidelity to cleaning stations, which means that individuals repeatedly return to preferred cleaning sites over extended periods of time. Cleaning stations also attract large aggregations of manta rays in many different parts of the world.
Due to their fixed location, cleaning stations are predictable and reliable sites for tour operators to take divers and snorkelers to encounter manta rays in the wild. It is very important however, that such encounters are conducted responsibly. Ideally divers and snorkelers should follow a code of conduct during interactions with manta rays on cleaning stations. These codes are designed to prevent any alteration of the natural behavior of manta rays, specifically the interruption of the cleaning process which has the potential to impact the health and well-being of individuals and possibly lead to long-term avoidance of cleaning sites.