Great white sharks are often depicted as formidable hunters. The idea that a great white can smell a single drop of blood from miles away is a common belief. This article explores the realities of their sense of smell and how it aids their survival.
The Great White’s Sense of Smell
A great white shark’s sense of smell is highly developed and crucial for detecting prey. Their nostrils, called nares, are located on the underside of their snout and are used exclusively for smelling, not for breathing. Water flows into these nares, passing over specialized olfactory sacs. These sacs contain olfactory lamellae, folds of skin that greatly increase the surface area for detecting odors.
Sensory cells lining these lamellae are highly sensitive, detecting minute concentrations of dissolved chemicals in the water. Messages from these cells go to the shark’s brain, which dedicates up to 18 percent of its mass to processing olfactory information. This allows the shark to identify scents and determine their direction, enabling them to follow a chemical trail.
How Far Can They Detect Chemical Traces?
While great white sharks have an acute sense of smell, the popular notion of them detecting a single drop of blood from miles away is an exaggeration. Sharks can detect certain chemical traces, such as amino acids released from injured fish, at concentrations as low as one part per 10 billion parts of water. This sensitivity means they can locate scents from hundreds of meters away, not typically miles. Under ideal conditions, with a strong scent plume and favorable currents, some sharks can detect and track odors from about a quarter of a mile away.
Environmental factors heavily influence scent detection distance. Water currents are crucial, as scent molecules must travel to the shark’s nostrils. The concentration of the chemical, water temperature, and specific compounds also determine how far and quickly a scent can be detected. While their olfactory system is highly sensitive, chemical dispersal in the vast ocean limits the actual range of detection.
Beyond Scent: Other Hunting Senses
Great white sharks rely on a multi-sensory system for hunting, with smell being one of several tools. They have acute hearing, detecting low-frequency vibrations from struggling prey over considerable distances. This helps them pinpoint food sources before they are visible. As they approach, their vision, especially adapted for low-light conditions, becomes more effective.
Sharks also have a lateral line system, sensory cells along their body that detect pressure changes and movements in the water. This system senses prey vibrations up to 250 meters (820 feet) away, even in murky water or darkness. Additionally, Ampullae of Lorenzini, jelly-filled pores on their snout, detect faint electrical fields generated by the muscle contractions of living organisms. These varied senses work in concert, allowing the great white shark to efficiently locate and pursue prey.