Eagle Ray, this beautiful type of ray is a frequent visitor to our water ways.
There are actually three distinct species. In the Indo-Pacific waters we have the Aetobatus Ocellatus or Ocellated Eagle Ray.
The adults can grow up to 5 meters in length and can have a wing span of up to 3 meters, weighing between 180 and 225 kg they are one of the larger species we have visiting the island.
Eagle rays are very distinct, from other ray species, because of their markings and beak. The Eagle Ray tends to be black, dark blue or grey in color (on its back or dorsal side) and are covered in individual spotted patterns, these ‘spots’ can be white, cream or yellow and the pattern and size of the ovals and rings can vary greatly from individual to individual. Scientist are using these unique patterns to track and trace individuals to learn more about this illusive species.
Their face is built in the same way as most Rays with its eyes and spiracles are found on the top of their body and their mouth and gills found on their white underside. The Eagle Ray has a distinct ‘duck-billed’ style snout which is broad and flat, it uses this ‘beak’ to dig in the sand for food. The eagle ray has teeth on the lower and roof of its mouth, these teeth and flatted to make two plates which it uses to get into the shells of crustaceans, its main source of food.
They have flat disc shaped bodies, like most Rays, and have a barbed tail they use for defense, similar to a Sting Ray, with between 2 and 6 barbs found near the base. Their tails are long and thin and resemble a ‘whip’ like style as they taper at the end.
Rays and sharks are very similar
Both being cartilaginous fishes meaning that their skeletons are made of cartilage not bone. Other species in this order are skates and swordfish and have the scientific name of Elasmobranchii. They have small ‘teeth’ that cover their bodies instead of scales and so are rough to the touch (we obviously shouldn’t be touching them any way!). Also, they all breathe through gills.
A lot of Rays breath by using small holes, known as spiracles, on the top of their heads. They suck water in and then push this water out through their gills, this is due to most rays being bottom feeders.
Eagle rays feed of crustaceans, crabs, octopus, shrimps and small fish. They stay in warm waters, between 24-27C, in shallower depths near coral reefs where they find a lot of their food, but they are not bottom dwellers, they have been seen to migrate large distances and swim in the middle of the water column. They have been observed swimming alone, in groups and in large schools where they monitor their speed to move together. Eagle rays are often seen leaping from the water and ‘flying’ above the waves before splashing back into the ocean, this type of behavior is not yet explained but could be to do with courtship and birthing for pregnant mothers.
They mate belly to belly with the male, or males, chasing the female bitting her pectoral fin to flip her over and then inserts his clasper. Mating only takes between 60-90 seconds but the females will then carry the young for up to a year. Eagle rays are interesting as they are Ovoviviparity, meaning that the young hatch from their eggs internally in the females, they feed from the ‘yolk’ of their eggs and are born alive. Each female will only give birth to around four to six pups in each pregnancy.
Eagle Rays have the largest brain to body ratio of all the rays and are the only ray to have multiple venomous barbs on their tail and live up to 25 years. Their majestic ‘flying’ style of swimming and patterned backs give them the title of ‘the most beautiful ray in the world’ and their silent calmness, even amongst humans, bring an almost ethereal feel as they slide past into the deep blue. Like most species they are still much of a mystery with little being known about their migration, different swimming patterns and schooling behaviors.
This species is classified as ‘near threatened’ on the IUCN red list
Their only natural predator take the form of sharks, in particular tiger sharks, lemon sharks, bull sharks, greater hammer heads and silver tips.
The main threat, as always, comes from humans. They are often caught as by-catch or out right hunted in some waters with unregulated over fishing. They are also killed to protect productivity in mollusk farming areas. Because of their beauty they are often caught and collected for the aquarium trade. In some areas they are now protected or partially protected, for instance South Africa has reduced the number of shark nets it sets due to the number of rays getting entangled and their resulting deaths.
So next time you see these eagles of the water take the time to pay them their dues and appreciate the wonderfully friendly calm they carry with them on their spotted backs. We are lucky to see them frequently on our dive sites.