The grey nurse shark, with its visible rows of sharp, pointed teeth, often evokes fear. Despite this intimidating appearance, these sharks are considered docile and pose little threat to humans. Their physical characteristics can be misleading regarding their true nature.
Understanding the Grey Nurse Shark’s Nature
The grey nurse shark, also known as the sand tiger shark or spotted ragged-tooth shark, has long, protruding, needle-like teeth visible even when its mouth is closed. These teeth are designed for grasping slippery prey like fish, squid, octopus, crabs, and lobsters, rather than tearing large chunks of flesh. They have stout, robust bodies, grey to grey-brown with a paler underside, often featuring reddish or brownish spots, especially in juveniles. They can grow up to 3.2 meters (10.5 feet) in length and weigh around 230 kilograms (500 pounds).
These sharks are slow-moving and prefer coastal waters, found near sandy bottoms, rocky reefs, caves, and shipwrecks at depths between 15 and 40 meters. They aggregate in these habitats. Their ability to gulp air from the surface and hold it in their stomachs allows them to achieve neutral buoyancy, enabling them to hover almost motionless. Grey nurse sharks are more active at night, hunting by stealth.
Actual Threat to Humans
Grey nurse sharks are known for their placid and timid nature, posing minimal danger to humans. Their large size and teeth historically led to misidentification as aggressive “man-eaters,” particularly in the 1950s and 1960s, resulting in intensive fishing efforts. However, scientific understanding has clarified that unprovoked attacks by grey nurse sharks are extremely rare, if they occur at all.
Reported incidents are linked to human provocation, such as disturbing the shark, or misidentification in low-visibility conditions. Their teeth are suited for holding small, slippery prey, and humans are far too large for them to consider as food. There have been no recorded human fatalities attributed to grey nurse sharks. Their dangerous perception stems from their intimidating looks, not their behavior.
Interacting with Grey Nurse Sharks
Grey nurse sharks have become popular subjects for ecotourism, attracting divers and snorkelers to their aggregation sites. Observing these sharks in their natural habitat is a unique and respectful experience. Divers follow codes of conduct to ensure minimal disturbance, such as maintaining distance and avoiding blocking their paths. Studies show that while diver presence can temporarily affect shark behavior, such as milling or active swimming, sharks return to normal once divers leave the area.
Grey nurse sharks face significant threats from human activities. Their populations have declined due to overfishing, accidental capture in fishing gear (bycatch), and habitat degradation. The east coast population in Australia, for example, is listed as critically endangered, while the west coast population is vulnerable. These sharks are slow to mature and have a low reproductive rate, producing only one or two pups every two years, which makes their populations vulnerable to these pressures.