The popular image of a shark as a relentless predator overshadows the biological reality of the over 500 known shark species. While a few species are apex predators that pose a risk to humans, the vast majority of sharks are not dangerous and actively avoid human interaction. These animals vary greatly in size, diet, and behavior, with most specializing in prey far too small or specific to include people. Understanding the traits that define these harmless species provides a more accurate picture of the ocean’s true diversity.
Characteristics of Non-Threatening Species
A shark’s threat level is determined by a combination of its size, dental structure, and feeding habits. Non-threatening species typically exhibit highly specialized diets, focusing on small fish, crustaceans, mollusks, or plankton. This dietary preference means they lack the biological need or instinct to target larger marine life, including humans.
Their jaw and tooth structure reflects these specific feeding needs, often featuring small, crushing plates or tiny, vestigial teeth designed for grinding hard-shelled invertebrates. Harmless sharks are often either very small and slow-moving or immense filter feeders that cannot physically consume anything larger than a small fish. Many of these species also prefer habitats far removed from human activity, such as the deep ocean or restricted coastal areas, further reducing the chances of accidental human encounters.
The Massive Plankton Eaters
The largest fish in the world, the Whale Shark (Rhincodon typus), is a visible example of a completely non-threatening species. Despite reaching lengths of up to 60 feet and weighing many tons, this colossal animal feeds almost exclusively on tiny organisms. Its feeding mechanism involves either ram-feeding, where it swims forward with its massive mouth open, or suction-feeding, where it gulps water to draw in plankton, small schooling fish, and krill.
The Basking Shark (Cetorhinus maximus), the second-largest fish, operates similarly, relying on its enormous mouth to filter zooplankton from the water. It uses specialized gill rakers to strain food as water flows through its mouth and out over its gills. These sharks may look intimidating as they slowly cruise near the surface, but their anatomy is not designed for predation on large animals, and their minuscule teeth are vestigial.
Docile Coastal and Bottom-Dwelling Sharks
Many smaller species that inhabit coastal shallows and the seafloor are harmless due to their sedentary nature. The Nurse Shark (Ginglymostoma cirratum), which can grow to about 10 feet, is a slow, bottom-dwelling species that spends most of its day resting. They are nocturnal hunters, using their small mouths to suck in invertebrates like conchs, lobsters, and crabs. Nurse Sharks are generally docile and only tend to bite if provoked or accidentally stepped on.
Angel Sharks (Squatina species) are named for their flattened bodies and broad pectoral fins that give them a ray-like appearance. These sharks camouflage themselves in the sand or mud, waiting to ambush small fish and crustaceans. Because they remain buried and still for long periods, they pose virtually no threat to swimmers, though they will deliver a defensive bite if directly disturbed or handled.
Smaller, localized species, such as the Bamboo Sharks (Chiloscyllium species) and Epaulette Sharks (Hemiscyllium ocellatum), are often found in tide pools or shallow reef crevices. Bamboo Sharks are small, slow-moving animals that use their teeth to crush invertebrates. The Epaulette Shark is notable for its ability to “walk” across the seafloor and even on land using its muscular paired fins.
Dogfish, including the Smooth Hound Sharks (Mustelus species) and Spurdogs (Squalus acanthias), are generally small to medium-sized sharks found in temperate waters globally. Smooth Hounds are named for their blunt, pavement-like teeth, which they use to crush crabs and other hard-shelled prey. These common, coastal sharks are not considered aggressive toward humans, reflecting their focus on preferred, smaller prey.