The shipwrecks in Isla Mujeres provide an incredible diving experience throughout the year. However, visitors can witness the annual migration of large groups of eagle rays between December and March. At this time, the area turns into a virtual "fly zone" due to their large number.
During the peak of the Spotted Eagle Ray season, it's possible to see 50-100 of these magnificent creatures gliding effortlessly above the wrecks, Gunboat 55 and Gunboat 58. These wrecks sit at a depth of between 24 mt/79 ft and 27 mt/89 ft.
The rays patrol vast territories in search of food, mates, and entertainment. The strong currents surrounding the shipwrecks attract the rays, and schools of them can be seen swimming serenely close above your head or frolicking in the water.
Diving these wrecks is not for new or inexperienced divers. It can be a challenging but equally rewarding dive, and there is a strict screening process to determine who is eligible to dive there. This ensures that it can be a safe and enjoyable dive for everyone.
If you are not an experienced diver, don't worry; we often see them gliding alone in MUSA or within the Manchones National Park. These dives have a shallower depth of 10 mt/30 ft and very little current.
The white sand and the crystal clear water around these areas allow, despite the depth, for some great photos to be taken of the wreck and the marine life (although a red filter or white balance will still make a significant difference to your photos).
What are Eagle Rays related to?
Eagle rays (Aetobatus narinari) are part of the Myliobatidae family. They are classified as fish and belong to the same group as sharks, a distinct species of Elasmobranchii, a subclass of cartilaginous fish (Chondrichthyes).
The family Myliobatidae includes three subfamilies.
Cow-nosed rays (Rhinopterinae): identified by their squarish, indented snout, and the fin under the snout has two lobes.
Eagle rays (Myliobatinae) are recognised by their diamond-shaped bodies and pointed mouths, which resemble an eagle's beak. They have a nearly straight front to the face, and the fin under the snout has only one lobe.
Manta rays (mobulinae): known for their large triangular pectoral fins and cephalic fins around their mouths. They have lateral eyes and spiracles. They also have large wing-like discs that are much wider than long, the ends pointed, no tail spine or only a rudimentary spine, and a small dorsal fin at the base of the tail. The head flaps are used to direct planktonic food items into the mouth. Despite their large size, Manta rays are incredibly graceful and elegant creatures.
What do they look like?
Eagle Rays are distinct from other rays due to their long tails and well-defined, rhomboidal bodies. They have a long, flat, rounded snout resembling an eagle's beak, from which they derive their name. Eagle Rays have thick heads and pectoral disks with sharply curved angled corners.
As mentioned, they are part of the Myliobatidae branch. They are active swimmers known to swim in the open ocean and do not lie motionless on the seafloor, like the closely related whiptail stingrays (e.g., southern stingrays).
Eagle rays are cartilaginous fish, like sharks and chimaeras, characterised by skeletons made of cartilage, not bone.
The stinging spines, located just behind the dorsal fin, are short in length and usually range from 2 to 6 in number. They have a barbed tip, recurved lateral teeth, and a forked root. These spines are venomous and can cause a painful sting when used for self-defence against potential threats. It is likely a protein-based venom because immersing the injured area in hot water appears to neutralise the pain. Despite having poisonous stingers, they are generally shy and non-threatening. Injuries can happen; though they are extremely rare, they are normally not fatal. Usually, casualties happen through freakish accidents. Most people tend to remember Steve Erwin's fatal encounter with a Stingray in Australia.
Eagle Rays come in varying shades of grey and brown and have white spots that form distinct patterns on their bodies. These patterns are unique to each individual, similar to human fingerprints, and can be used to track them. Their abdomen is typically solid white.
To identify them, you can use the distinctive patterns in the areas of rings or spots on their pelvic fins. If you come across an Eagle Ray that you want to identify, make sure to capture an image or video of the pelvic fins or the area near the tail to submit it for identification. Along with the image or video, provide information about the dive site, including its GPS coordinates if possible, the date of the sighting, the approximate depth, and the number that you saw. This will help with accurate identification.
Submit your findings to
How big do they grow?
Spotted eagle rays grow to a maximum length of around 5mt/ 16 feet, including the tail, and 230 kg/ 507 pounds. Their wingspan reaches a maximum width, from tip to tip, of 190 cm/6 ft for males and around 226 cm/7.5 ft for females; the spotted eagle ray is one of the largest eagle rays, with only the mantas growing bigger.
How long do they live?
They can live as long as 25 years, although one lived in captivity for 30.
How much do they weigh?
They have a recorded maximum weight of 238 kg.
What do they eat?
Eagle rays are a type of predator that uses organs called Ampullae of Lorenzini, which are jelly-filled pores on their snouts that can detect the weak electrical fields created by the muscles of other animals hiding in the seabed.
They develop rows of broad fusiform teeth, forming a continuous crushing surface on their upper and lower jaws, which they can crush and grind up hard-shelled bottom-living food like a mortar and pestle. Sharks and rays have the remarkable capacity to continuously regenerate their teeth using a conveyor-belt-like replacement system.
Eagle Rays excavate sand around their prey by blasting water out of their gills, leaving telltale pits that can be about a foot across with steep sides.
Although they prefer to consume molluscs and crustaceans, they eat small fish, shrimp, octopus, and worms. However, most of their diet comprises shellfish, clams, snails, and hermit crabs.
How do they breed?
The females of this species are noticeably larger than the males, taking approximately 15 years to sexually mature when the wing span reaches 125-135 cm (50-53 inches).
During the mating season, one male - or sometimes a group of males - will pursue a female. When a male approaches a female, he uses his plate-like teeth to grab her dorsum, leaving telltale round scars. He will then roll her over by taking hold of one of her pectoral fins, which are located on either side of her body. Once he is on her ventral side, the male inserts a clasper into the female, joining them with both undersides, venter to venter. The entire mating process typically lasts between 30 to 90 seconds. Females have been observed to mate in this manner with up to four males over a short time period.
Eagle rays are ovoviviparous; the term aplacental viviparous is more commonly used now, meaning the eggs develop and hatch inside the body. They reproduce via internal fertilisation but do not connect to their young through a placenta, like in most mammals. Instead, embryos live off of energy obtained from yolk sacs, and only after the juveniles can survive on their own does the mother give birth to her young (1-5 pups per litter). When the pups are born, they already have a wingspan of about 15 inches. Generally, the gestation period is around 12 months.
This low reproductive potential and late sexual maturity, along with their natural rarity, contribute to experts considering spotted eagle rays as ‘near threatened’ with extinction.
Where they give birth is a mystery. It is assumed that in Quintana Roo, they enter sancutaries such as Nitzuc, Sian Ka'an or Xcalak, where the mangroves protect them. Eagle Rays are known to sometimes give birth under stress.
Where do they live?
Spotted eagle rays are found in warm waters along the open coast worldwide, preferring temperatures between 24 to 27 °C (75 to 81 °F). They are mostly associated with coral reefs and sometimes move into protected bays for feeding or mating. Although considered coastal species, their worldwide distribution indicates that some individuals may migrate long distances over deep water. Further genetic research may reveal that spotted eagle rays in different ocean basins, such as the Atlantic versus the Pacific oceans, are separate species.
While sometimes found alone during the non-breeding season, Eagle Rays more frequently form large schools called fevers. Sometimes, up to several hundreds of animals together at once.
Why do they jump out of the water?
Scientists have not reached a consensus on the explanation for the phenomenon of jumping out of the water. They have proposed different hypotheses to explain this behaviour.
One theory suggests that it is a form of courtship display to attract females.
Another theory suggests that it helps the Eagle Rays get rid of remoras and parasites. Some scientists think this behaviour may also function as a homing system, as the jumping could indicate their position to isolated individuals. This theory is based on the idea that group jumping creates a sound that can be heard miles away. Finally, some scientists believe they simply jump out of the water for fun.
Are they endangered species?
This species is not intentionally caught by commercial fisheries, but it is sometimes caught accidentally when other species are being targeted. This ray is rarely eaten due to the poor quality of the flesh. Instead, it is used for fishmeal and oil. Sometimes, the meat of the rays may be substituted and sold off as other meat, only identifiable by genetic testing.
Spotted eagle rays are also at risk due to habitat loss, harmful algal blooms, and entanglement in fishing gear. These factors, as well as their low reproductive rate, make them vulnerable to population declines.
Additionally, it is sometimes caught alive and displayed in public aquariums.
The global population of this species is decreasing, and it is essential to monitor their numbers closely in case conservation efforts are needed if the population becomes dangerously low. The Spotted Eagle Ray has been listed as Endangered since 28 July 2020.
You can check their current status with IUCN here.
The harvesting, capturing, selling, or trading of Spotted Eagle Rays is illegal. It is crucial to promote their conservation through education and awareness.
What more do we need to know about them?
The ability to track eagle rays and know more about them is important, although tracking is a costly venture; the trackers can fall off the rays after only a few months. Because of this, there is still so much to learn. The organisation for Eagle Rays in the Cancun/ Isla Mujeres area strives to know more about the fevers of rays in this area. Why are they here? Do they return to breed and give birth? Where do they give birth? Do they travel from a protected National Park to an area of fishing and out of our ability to protect them?
How can we help?
Setting up tracking for Eagle Rays is an expensive but necessary process to better understand these creatures. There are two options for tracking them: GPS tracking and acoustic telemetry. Currently, Bull Sharks in Playa del Carmen are being tracked using acoustic telemetry, and an acoustically tagged Eagle Ray from Florida was recently detected on their receivers. To gain more insights into these animals, it would be ideal to set up tracking in Isla Mujeres. There is still much that needs to be learned about these creatures, and donating to the Spotted Eagle Ray Project - Mexican Caribbean can help make this possible.
If you would like to donate or contact them for further information, you can contact them here.
Facts About Spotted Eagle Rays
A group of Spotted Eagle Rays is called a Fever. A group of Manta rays is called a Squadron, and a group of sharks is called a Shiver.
Spotted eagle rays grow to a maximum length of around 5mt/ 16.4 feet, including the tail, and 230 kg/ 507 pounds. Their wingspan reaches a maximum width, from tip to tip, of 190 cm/6 ft for males and around 226 cm/7.5 ft for females.
They are believed to live for as long as 25 years.
Spotted eagle rays can be found from the surface to just over 60 mt/196 feet deep.
Spotted eagle rays can leap their entire bodies out of the water while swimming close to the surface.
Spotted eagle rays have venomous spines on their tails that can be used as a defence mechanism. Their stinger secretes venom that can cause intense pain and bacterial infection. Hot water is a common remedy for alleviating the pain.
Spotted eagle rays possess plate-like teeth to crush their preferred prey, including clams, oysters, sea urchins, and shrimp. They use the plates of interlocking teeth on their upper and lower jaws to grind away at their hard-bodied prey, much like a mortar and pestle.
The large rostrum, or “nose,” of a Spotted Eagle Ray creates an increased surface area full of electro-sensory pores called Ampullae of Lorenzini that help them detect the weak electrical fields created by the muscles of other animals hiding in the seabed.
Male eagle rays bite the wings of their mate as part of their courtship behaviour, leaving telltale round scars.
The females give birth to live pups (1-5 at a time), and when born, they are already independent and have a wingspan of approximately 15 inches.
If you are doing the Pocna Dive Center Distinctive Speciality, you must complete the following exam and complete the final window.
If you just want to test your knowledge, have a go; it's free.
Part of the proceeds of every course completed will be donated to the Spotted Eagle Ray Project - Mexican Caribbean.
Gracias a Spotted Eagle Ray Project - Mexican Caribbean por su ayuda, información y material para este proyecto.
Marinelife identification : Rays Species in Cabo San Lucas. (n.d.). Cabo Private Guide. https://www.caboprivateguide.com/blog/cabo-san-lucas-types-of-rays#:~:text=Eagle%20rays%20have%20a%20distinctive,cephalic%20fins%20around%20their%20mouths.
Oceana. (2023, June 27). Spotted Eagle Ray - Oceana. https://oceana.org/marine-life/spotted-eagle-ray/#:~:text=Fun%20Facts%20About%20Spotted%20Eagle%20Rays&text=Spotted%20eagle%20rays%20grow%20to,feet%20(60%20m)%20deep.
Two Oceans Aquarium | Eagle rays: everything you need to know about. . .. (2022, November 1). Two Oceans Aquarium. https://www.aquarium.co.za/news/eagle-rays-everything-you-need-to-know-about-the-oceans-cutest-ray
Wikipedia contributors. (2023a, October 15). Eagle ray. Wikipedia. https://en.wikipedia.org/wiki/Eagle_ray
Wikipedia contributors. (2023b, November 20). Spotted eagle ray. Wikipedia. https://en.wikipedia.org/wiki/Spotted_eagle_ray#:~:text=This%20ray%20can%20be%20identified,are%20several%20venomous%2C%20barbed%20stingers.
Spotted eagle Ray. (n.d.). https://www.nausicaa.fr/en/my-visit/animals/spotted-eagle-ray#:~:text=This%20species%20reaches%20sexual%20maturity,and%20hatch%20inside%20its%20body.
Rasch, L. J., Cooper, R. L., Underwood, C. J., Dillard, W. A., Thiery, A. P., & Fraser, G. J. (2020). Development and regeneration of the crushing dentition in skates (Rajidae). Developmental Biology, 466(1–2), 59–72. https://doi.org/10.1016/j.ydbio.2020.07.014
Summer Series 5: Is it a fish, is it a bird? . . .It’s an eagle ray! (2023, March 20). NIWA. https://niwa.co.nz/news/summer-series-5-is-it-a-fish-is-it-a-bird-%E2%80%A6its-an-eagle-ray#:~:text=Eagle%20rays%20belong%20to%20the,of%20cartilage%20rather%20than%20bone
Aetobatus narinari: Dulvy, N.K., Carlson, J., Charvet, P., Bassos-Hull, K, Blanco-Parra, MP, Chartrain, E., Derrick, D., Dia, M., Diop, M., Doherty, P., Dossa, J., De Bruyne, G., Herman, K., Leurs, G.H.L., Mejía-Falla, P.A., Navia, A.F., Pacoureau, N., Pérez Jiménez, J.C., Pires, J.D., Seidu, I., Soares, A., Tamo, A., VanderWright, W.J. & Williams, A.B. (2020). [Dataset]. In IUCN Red List of Threatened Species. https://doi.org/10.2305/iucn.uk.2021-1.rlts.t42564343a2924463.en
Bassos‐Hull, K., Wilkinson, K. A., Hull, P. T., Dougherty, D. A., Omori, K. L., Ailloud, L. E., Morris, J., & Hueter, R. E. (2014). Life history and seasonal occurrence of the spotted eagle ray, Aetobatus narinari, in the eastern Gulf of Mexico. Environmental Biology of Fishes, 97(9), 1039–1056. https://doi.org/10.1007/s10641-014-0294-z
Direct, T. S. (2023, October 13). GPS tags for marine animals. https://www.linkedin.com/pulse/gps-tags-marine-animals-tracking-system-direct
Comments