The Manta Rays are the largest species of rays in the world. The name “manta” is Spanish for cloak or blanket. Manta Rays are classified as Cartilaginous Elasmobranch Fishes which means they are very closely related to all other rays as well as sharks. Unlike most other ray species, they do not have a stinger.
Manta Rays belong to the Mobulidae family, which consists of the Genus Manta (Manta rays) and the Genus Mobula (devil rays). There are 2 species of Manta Rays and 9 species of Mobula devil rays. It was only recently (2009) that researcher Dr. Andrea Marshall discovered that there are two different species of Manta Rays: the Coastal Reef Manta Ray (Manta alfredi) and the Giant Oceanic Manta Ray (Manta birostris). The Coastal Reef Manta Ray is smaller of the two; with a wing span up to 4.5 meters whereas the Giant Oceanic Manta Ray can reach up to 7 meters wing tip to wing tip. Mobula rays are the smallest of the group with wingspans generally of less than 2 meters.
Manta rays are found in tropical, sub-tropical and temperate waters in all the world’s major oceans, preferring water temperatures above 20⁰C.While M. alfredi tends to stay in shallow coastal waters, migrating smaller distances along the coast, M. birostris and Mobula rays are more pelagic, living in open oceans and travelling with the currents. M. birostrisis often referred to as an ‘ocean wanderer’, traveling great distances across open oceans, its movement patterns one of the least known of the Manta Rays. M. alfredi tend to form ‘resident’ populations, such as the population of Manta Rays that we have here at Ningaloo Reef.
Manta rays have the largest brain relative to body size compared to any other fish species, and sophisticated senses for hearing, touch, vision and electrosensory systems, therefore they are believed to be highly intelligent and social animals. It is unsure how long they live but researchers believe it is as long as 50 years and possibly up to 100 years of age.
Manta and mobula rays are filter feeders, consuming large quantities of zooplankton in the form of shrimp, krill and planktonic crabs. M. alfredi are often seen at Ningaloo Reef foraging for food and display a number of different feeding techniques such as line feeding, surfacing skimming, bottom feeding and barrel rolling. Moving through the water with their mouths wide open, they unfurl their horn-like cephalic lobes from either side of their giant mouths to funnel water into their mouths which is then filtered through a highly developed filtration system (gill rakers). While Manta rays tend to be solitary, they can form large schools when food is abundant. Adult manta rays can consume 27 kilograms (27,000 grams) of food per day!
Manta rays exhibit very speculator mating behaviors, and are often observed here in Coral Bay. Courtship is displayed as a ‘mating chain’ or ‘train’. One female manta ray will be pursued by one, two sometimes up to 8 male manta rays, forming a train the eager male manta rays jostle for best position behind the female. The males will mimic every move of the female, making this courtship period look more like a dance. Eventually one male will mate with the female by biting her left pectoral fin, turning her over where they mate belly to belly. Gestation takes between 12 – 14 months. Manta rays reproduce via aplacental viviparity, meaning they give birth to live young which are hatched from an egg inside the female’s uterus. The female manta rays give birth to a single pup (although occasionally they may also give birth to twins), which measures approximately 1.2 meters across from wing-tip to wing-tip at birth.The pups become active as soon as they have rolled out their wings and are independent of their mother from birth. No reported sightings of a manta giving birth in the wild have been documented; however it has been captured on film in an Aquarium in Japan. In the wild the female probably selects a safe location, like a sheltered bay, within which to give birth. Research has found that a female manta may only average one pregnancy every five to six years, not reaching sexual maturity for at least 15 years. This is an extremely low reproductive rate and has significant implications for the management and conservation of this species.