Sleeper sharks, inhabitants of the ocean’s colder, darker depths, often spark curiosity due to their imposing size and mysterious lives. This article explores their characteristics, habitats, and documented interactions to assess the potential danger they represent.
What are Sleeper Sharks?
Sleeper sharks are large, slow-moving sharks primarily found in deep, cold waters across various oceans. The Pacific sleeper shark (Somniosus pacificus) is a well-known species, commonly reaching 3.65 meters (12 feet) and weighing 318 to 889 kilograms (700 to 1,958 pounds). While typically dark gray to black, these sharks possess a cylindrical body, a short, rounded snout, and two dorsal fins of similar size.
These sharks are distributed across temperate waters in the North Pacific, including areas from Japan to the Bering Sea, and down to Baja California, with some sightings in the South Pacific. They are both predators and scavengers, using specialized lips and teeth to suction and cut prey, which includes deep-sea fish, squid, crabs, and even larger marine mammals like seals and sea lions, as well as carrion. Despite their name, suggesting a sluggish nature, recent research indicates they are active swimmers that move continuously through the water column, often gliding with minimal body movement to approach prey undetected.
Assessing Their Danger to Humans
Sleeper sharks are generally not considered a danger to humans. Their primary habitat in extremely cold, deep waters means encounters with people are rare. They typically reside far from coastal areas and human activities, preferring depths from the surface in higher latitudes to over 2,000 meters (6,560 feet) in lower latitudes. This deep-water preference limits opportunities for interaction.
Their behavior also contributes to their low threat. Sleeper sharks are known for their slow and calm demeanor, even when caught. This contrasts with other shark species that might thrash or struggle vigorously. Their feeding habits, involving stealthy predation and scavenging on deep-sea organisms, do not typically involve aggressive tactics towards humans. Consequently, there are virtually no instances of these sharks being provoked into an attack.
Observed Behavior and Human Interactions
Human encounters with live sleeper sharks are uncommon, primarily limited to accidental bycatch in deep-sea fishing or rare scientific observations using remotely operated vehicles and submersibles. When observed, their behavior reinforces their non-aggressive nature. For instance, studies using baited cameras have shown Pacific sleeper sharks exhibiting a “queueing” behavior when feeding on carcasses, where individuals politely yield their position to others, suggesting a social structure that minimizes conflict.
There are no documented cases of unprovoked attacks on humans by sleeper sharks. While their Greenland shark relatives have anecdotal reports of investigating divers, verified attacks are absent for either species. The rarity of encounters and their docile nature support the conclusion that sleeper sharks do not pose a significant threat to people.