Spotted Eagle Ray
The Spotted Eagle Ray is one of the most beautiful creatures on Earth, and it’s found mostly around tropical waters. This ray has a very wide diamond-shape pectoral disk that can reach over 9ft across, and is a dramatic deep black color dotted with bright white spots or rings. It grows up to about 8ft long, and when including its incredibly long whip-like caudal fin, it has been measured as reaching nearly 17ft long. It prefers bay and reef habitats, but will school together in large numbers to cross large distances in open water. It is not a particularly popular species, and when caught, it makes loud noises and should be handled with extreme care, as it delivers a painful bite.
The spotted eagle ray, Aetobatus naranari, is the type species of the monotypic genusAetobatus, within the familyMyliobatidae, and the only member of the subfamilyAetobatinae. The etymology of the generic name Aetobatus derives from the Ancient Greek words ἀέτος (áēto), meaning “swimmer”, and βαυκῶν (bathukón), meaning “duck”. This refers to the shape of the head resembling a swan, and the fact that it swims with its mouth closed like a duck. The specific epithet naranari is derived from the Tupian languages spoken by indigenous peoples living along the Amazon River basin in South America. These people call the spotted eagle ray mamãnara (“mother”).
As a cartilaginous fish, the spotted eagle ray has a large disk-shaped body covered in bony plates, similar to sharks and rays. Adults grow up to 2 meters long and weigh about 50 kg. They are found in shallow coastal waters around continental shelves, where they feed mainly on small crustaceans such as crabs and shrimp. Their diet consists mostly of plankton, although they occasionally eat larger prey items such as fishes and cephalopods. In some areas, they are known to take advantage of the discarded carcasses of dead whales, dolphins and sea turtles.
Description and behavior
The spotted eagle ray (Aetobatus narinari), also known as the Narina Ray, is a large species of stingray in the family Dasyatidae. This species inhabits coastal waters around Australia and New Guinea, including the Coral Sea, and the Great Barrier Reef off northeastern Queensland. They feed primarily on mollusks such as octopus, squid, small fish, crabs, and sea cucumbers, although some individuals have been seen eating jellyfish.
Spotted eagle rays are often found in groups, sometimes numbering into the thousands. These rays are nocturnal animals, spending most of their lives resting beneath coral reefs or rocky outcrops during daylight hours. When feeding, they use their flattened heads to sweep over the seafloor searching for prey. They typically rest on the bottom, near crevices or among rocks, where they shelter from predators like sharks and crocodiles.
Although it is possible to catch spotted eagle rays while spearfishing, they are too fast for fishermen to reel in without serious injury. Like many members of its genus, spotted eagle rays have been observed performing “dance displays” to attract mates. During courtship, males perform headstands above females, waving their pectoral fins in circles as they slowly swim forward. If a female accepts his advances, she rises vertically and the male follows her. After mating, the pair retreats to deeper water to give birth. Females bear litters of one to five young every three months.
In captivity, spotted eagle rays exhibit aggressive behaviors toward humans, biting and thrashing against handlers. They are highly territorial and will attack anything that threatens their territory. In addition, captive specimens tend to become stressed and agitated by human contact.
Feeding and diet
Spotted eagle rays are omnivorous; their diets consist of both plant material and animal matter. They eat mostly soft tissue such as algae, plankton, zooplankton, detritus, and carrion. Their teeth are adapted for crushing and grinding food items into smaller particles, and their jaw bones are reinforced with cartilage.
Eagle rays feed primarily during daylight hours, although they can remain active throughout the night. During daytime feeding periods, they prefer shallow waters near shorelines where there is abundant light and vegetation. However, they have been known to venture out into deeper water during nighttime hours. In addition, they tend to move away from areas with strong currents, turbidity, and large amounts of suspended sediment.
The species feeds most often within 0–2 meters (0–6 ft) of the surface, though some individuals have been observed diving up to 5 m (16 ft). This behavior varies among individuals and populations. Individuals typically consume about one gram per hour, though larger animals have been recorded consuming up to 3 g/hr. A study conducted off the coast of Hawaii found that females consumed 2.5 times more prey than males.
A few studies suggest that spotted eagle rays may be able to detect prey visually. Another suggested that they use echolocation to locate prey. Research published in 2010 suggests that spotted eagle rays rely heavily on smell to find their food.
Spotted eagle ray behavior
Eagle rays are known to be very curious animals. During daylight hours, they often approach boats, surfacing just feet away to investigate. If you are lucky enough to see one swimming around in shallow water, it is likely to come up close to observe what you are doing. In fact, some people claim that they are too inquisitive to keep in captivity.
Their feeding habits remain somewhat mysterious because they do not feed by sucking in prey like most bony fish. Instead, they use a suction disk located on each side of their head to draw food into their mouths. This disk is covered by skin called the epidermis, which is usually brownish gray. However, in young spotted eagle rays, the coloration is much lighter.
The disk is attached to muscles that allow it to open and close. When the disk opens, it creates a vacuum effect that pulls in small organisms such as plankton, amphipods, and polychaete worms. These creatures are drawn in by the force of gravity and are carried along by currents of water. On occasion, eagle rays will actually swallow large organisms whole, such as crabs or sea stars.
In addition to being attracted to boat wakes, eagle rays are also attracted to baitfish. Some studies have shown that they actively seek out baited hooks, while others have found that they are simply attracted to moving objects. Researchers believe that the attraction is due to the presence of pheromones emitted by baitfish.
Anatomy and morphology
Spotted eagle rays are generally considered to be medium sized rays, measuring about 2–4 m (6–13 ft) long and weighing about 250 kg (550 lb). Like many species of stingray, they possess a venomous spine embedded in their tail fin. Unlike most stingrays, however, the spine is not used for defense against predators, but rather for mating purposes.
The spotted eagle ray is viviparous, meaning it gives birth to live young rather than laying eggs like most fish do. This reproductive strategy allows embryos to develop inside the mother without being exposed to the outside environment. In contrast, sharks give birth to fully developed offspring.
Eggs are fertilized externally by spermatozoa, and the developing embryo feeds on a yolk sac. After about 90 days gestation, the fetus becomes free swimming within the amniotic fluid. At hatching, the baby rays measure about 2 cm long and weigh approximately 0.5 g. They are born tail first, and the umbilicus closes shortly after birth. Their eyes open at around 18 hours old.
The newborn rays are nursed for three weeks, during which time they grow rapidly. At 5 months old, they reach sexual maturity. A single breeding season typically takes place between July and October. During this period, females produce up to 20 million eggs per day. The average lifespan of a female is 10 years.
The spotted eagle ray is distributed throughout the world in tropical and subtropical marine habitats.
In the western Atlantic Ocean, this species lives in coastal waters from North Carolina and Florida to Brazil.
This ray can be found from Mauritanian shores to Angola in the eastern part of the Atlantic Ocean.
In the Indo-West Pacific region, it occurs in the Indian Ocean from South Africa to Hawaii and south to Australia. It also lives in the Red Sea and around Japan and southern China.
In the eastern Pacific Ocean, the spotted eagle ray inhabits the Gulf of California and Galapagos Island.
Danger to Humans
Spotted eagle rays are generally shy animals and are often found alone, swimming slowly around coral reefs. But they are becoming increasingly rare, according to the International Union for Conservation of Nature Red List. In recent decades, there has been a decline in numbers across most of their range, including off Australia, New Zealand, Madagascar, Sri Lanka, Indonesia and Malaysia. This is primarily because the rays are hunted for food, and many populations are now threatened by habitat loss and degradation.
The species is potentially dangerous to humans due the venomous tail spurs that can cause serious wounds. There have been several fatal attacks in the past few years. A diver died following an attack while diving near the Maldives, and another person died after being stung during a stingray encounter in Florida.
Fun Facts About Spotted Eagle Rays
Spotted eagle rays are one of the largest species of ray in the world. They belong to the family Myliobatidae, which includes hammerhead sharks, sawsharks, wobbegongs, and nurse sharks. This group of fish are often referred to as batoids because of their elongated bodies and distinctive dorsal fins.
The spotted eagle ray is named for its large size and striking pattern. Its dorsal fin resembles an eagle’s head and neck, while its pectoral fins resemble those of a shark. In addition, it has a long, slender snout that ends in a blunt, rounded nose.
Like many other members of the myliobatid family, spotted eagle rays are slow swimmers. They move slowly along the bottom of the ocean, usually close to shorelines or coral reefs. They feed primarily on crustaceans such as crabs, shrimp, shrimps, and amphipods. Smaller individuals eat smaller prey items, while larger individuals consume larger prey.
Spotted eagle rays have two rows of sharp, needle-like teeth in each jaw. These teeth help them crush hard-shelled invertebrates. Each tooth is covered with a protective enamel cap that helps protect the animal from injury.
Spotted eagle ray skin contains a substance called uric acid, which makes it appear black when viewed under certain lighting conditions. When the rays are disturbed, they release a cloud of dark gas that obscures vision.
The spotted eagle rays’ diet consists mainly of small crustaceans and mollusks. However, they also eat some fish, especially juveniles.
The spotted eagle is not aggressive toward humans, but it will defend itself if provoked. It may even bite if cornered. Like all rays, these creatures are harmless unlesshandled roughly.
The spotted eagle is ovoviviparous (eggs hatch inside the mother). Females give birth to live young every 2–3 months. The gestation period lasts about 4 months.
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