Devil rays, encompassing both Mobula and Manta species, are magnificent creatures found in tropical and temperate waters worldwide. Despite their formidable size and intimidating nickname, they pose virtually no threat to humans. These animals are non-aggressive filter feeders.
The Source of the Fear
The common name “devil ray” originates from the two prominent, fleshy appendages protruding from the front of the head. These structures, known as cephalic fins or lobes, resemble horns when unfurled, leading to the association with a devilish figure. These “horns” are modified parts of the pectoral fins that serve a utilitarian purpose.
These cephalic fins are flexible and can be rolled up while swimming, but they are extended to funnel plankton-rich water into the ray’s mouth while feeding. The fear surrounding devil rays is often conflated with that of stingrays (Dasyatidae family), which possess a venomous, barbed tail used for defense. Giant manta rays and most Mobula species do not possess a functional barbed stinger. Some Mobula species retain a vestigial spine, but it is typically encased and harmless.
Size and Filter Feeding Behavior
The sheer size of these animals is often the only intimidating feature, yet it indicates their harmless nature. Giant oceanic manta rays (Mobula birostris) can reach a disc width of up to 7 meters (23 feet). Even smaller Mobula species can exceed 1.1 meters. This immense size is supported by a diet consisting entirely of microscopic organisms, meaning they have no mechanism to prey on large animals like humans.
As obligate filter feeders, their anatomy is adapted to consume zooplankton, small crustaceans, and krill. They swim with their wide, terminal mouths open, drawing in water that passes over specialized gill rakers. This process filters the tiny food particles before the water is expelled through the gill slits.
Their mouth structure is incompatible with biting or attacking anything larger than their prey, as they lack the sharp teeth or predatory mechanisms of a carnivore. Their behavior is characterized by a curious but cautious temperament. They often approach divers or boats out of interest, not aggression, and generally ignore human presence unless they feel harassed or threatened.
How to Interact Safely
Encounters with these rays require a code of conduct based on passive observation to ensure the safety and well-being of both the animal and the human. Snorkelers and divers should maintain a respectful distance, often suggesting a minimum separation of 3 to 4 meters (10 to 13 feet). This distance prevents disturbance and allows the ray to behave naturally.
Never chase, touch, or attempt to ride a ray, as these actions can cause stress, disrupt natural feeding patterns, and interfere with their movements. The only potential danger in an interaction arises from human interference, such as a panicked ray accidentally colliding with a diver if its path is blocked. Many Mobula and Manta species are listed as Vulnerable or Endangered, making adherence to these guidelines important to protect them from harassment and entanglement.