Giant Oceanic Manta Ray

The giant oceanic manta ray, also known as the giant manta ray or oceanic manta ray (Mobula birostris), is a species of ray in the Mobulidae family and holds the distinction of being the largest type of ray in the world. It is distributed globally and typically inhabits tropical and subtropical waters, but can also be found in temperate regions. Previously, it was categorized under the genus Manta alongside the smaller reef manta ray (Mobula alfredi); however, DNA testing revealed a closer genetic relationship to rays of the genus Mobula, leading to its reclassification as Mobula birostris.

The giant oceanic manta ray can reach impressive lengths of up to 9 meters (30 feet) and has a disc size of approximately 7 meters (23 feet), weighing around 3,000 kilograms (6,600 pounds). However, the average size frequently observed is 4.5 meters (15 feet). This species has a dorsoventrally flattened body and prominent triangular pectoral fins on either side of the disc. At the front, it possesses cephalic fins, which are extensions of the pectoral fins. These fins can either be coiled up for swimming or extended outward to guide water into the large, rectangular mouth when feeding. The ray's teeth are confined to a central band of 18 rows in the lower jaw.

The eyes and spiracles, which function as modified gill slits, are positioned on the side of the head behind the cephalic fins, while the gill slits are located on the ventral surface. Additionally, it features a small dorsal fin and a lengthy whip-like tail, which lacks the spiny appearance found in closely related devil rays (Mobula spp.). Instead, the tail possesses a knob-like bulge near its base. The smooth skin of the giant oceanic manta ray showcases conical and ridge-shaped tubercles. The dorsal surface of the ray can be black, dark brown, or steely blue, occasionally exhibiting a few pale spots and typically bordered by a pale edge. In contrast, the ventral surface is white, sometimes displaying dark spots and blotches. These distinctive markings are often used for individual identification. Despite similarities in appearance, Mobula birostris can be differentiated from Mobula alfredi through specific characteristics.

When distinguishing between the oceanic manta ray and the reef manta ray, several physical distinctions exist. The oceanic manta ray surpasses the reef manta ray in size, with an average length of 4 to 5 meters compared to 3 to 3.5 meters. However, size may be misleading when determining the species, especially when observing young rays. Therefore, relying on the color pattern remains an effective method of differentiation. The reef manta ray boasts a dark dorsal side with two lighter areas on top of its head, forming a nuanced gradient of its dominant dark coloration. Additionally, the longitudinal separation between these lighter areas creates a "Y" shape. Conversely, the dorsal surface of the oceanic manta ray is deeply dark, and the two white areas are distinctly marked without a gradient effect. The line separating these white areas forms a "T" shape.

A distinction can also be made based on ventral coloration. The reef manta ray exhibits a white belly often adorned with spots between the branchial gill slits, as well as spots scattered along the trailing edge of its pectoral fins and abdominal region. In contrast, the oceanic manta ray also has a white ventral coloration, but with clustered spots primarily situated in the lower region of its abdomen. Notably, its cephalic fins, the interior of its mouth, and its gill slits often display a black pigmentation.

The giant oceanic manta ray enjoys a broad distribution spanning tropical and temperate waters worldwide. In the Northern Hemisphere, it has been spotted as far north as southern California and New Jersey in the 🇺🇸 United States, Aomori Prefecture in 🇯🇵 Japan, the Sinai Peninsula in 🇪🇬 Egypt, and the Azores in the northern Atlantic. Its presence extends south in the Southern Hemisphere, reaching regions such as 🇵🇪 Peru, 🇺🇾 Uruguay, 🇿🇦 South Africa, and 🇳🇿 New Zealand. As an oceanic species, it spends the majority of its life far from land, utilizing ocean currents and migrating to areas where nutrient-rich upwellings support abundant zooplankton. The giant oceanic manta ray is frequently found in association with offshore oceanic islands.

Given its substantial size and remarkable speed (capable of reaching speeds up to 24 kilometers per hour when escaping danger), the giant oceanic manta ray faces few natural predators that pose a threat to its survival. Large sharks and dolphins, including the tiger shark (Galeocerdo cuvier), the great hammerhead shark (Sphyrna mokarran), the bull shark (Carcharhinus leucas), the false killer whale (Pseudorca crassidens), and the killer whale (Orcinus orca), have the capacity to prey on this ray. Nonlethal shark bites are commonly observed, with the majority of adult individuals bearing the scars of at least one attack.