Harbour Porpoise

Fascinating facts about the Harbour Porpoise

• A harbour porpoise's brain is proportionally larger than a human's — yet it weighs just 600 grams and fits inside a skull the size of a grapefruit. They use this neural real estate to process echolocation clicks at lightning speed, adjusting their sonar 600 times per second as they hunt in murky water where visibility drops to a few centimetres. This makes them arguably the most acoustically sophisticated hunters in the Northern Hemisphere.
• They die in fishing nets at a rate of 650,000 per year worldwide — more cetaceans killed by accident than any other marine mammal. A single gillnet, invisible in dark water, can trap dozens in a single night. Some populations have lost up to 90% of their members in half a century, despite being listed as Least Concern, because the kills happen quietly in waters most people never see.
• A harbour porpoise's heart beats only 40 times per minute while diving — half the rate of a resting human — yet somehow delivers oxygen to a brain working at full cognitive load. Their blood contains three times more red blood cells than ours, and their spleen contracts to release a massive oxygen reserve the moment they submerge. They can hold their breath for up to 30 minutes, though most dives last only 30 seconds.
• They are the smallest cetaceans in the Atlantic, rarely exceeding 1.9 metres — about the length of a man lying down — yet their clicks travel kilometres through water and bounce back in exquisite detail. A mother recognises her calf's unique click signature within hours of birth and maintains a conversation with it for the first year of life. Separate them by a few hundred metres, and they'll click back and forth until they reunite.
• Harbour porpoises are the only cetaceans that seem indifferent to boats and humans — they'll surface near you without fanfare, exhale with a soft chuff, and vanish. This shyness made them invisible to science for centuries; we only began understanding their lives in the 1980s. Even now, they remain one of the least-studied marine mammals, despite living in some of the world's busiest shipping lanes.

At a glance

About the Harbour Porpoise

In the dark, mysterious waters of the coastal shallows, the harbour porpoise glides with effortless stealth, its sleek, grey body undulating as it pursues the shimmering schools of fish that dart through the waves. With a gentle, almost languid pace, it navigates the tangled seaweed forests and rocky outcrops, its sensitive echolocation guiding it through the murky depths with uncanny precision. As it breaks the surface, its soft, blowing exhalation is a fleeting glimpse into the secret world of this enigmatic, yet remarkably resilient creature.

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