American Signal Crayfish

Fascinating facts about the American Signal Crayfish

• A crayfish can taste with its feet. Chemoreceptors covering their walking legs and claws detect food chemicals from up to 2 metres away in murky water — letting them hunt in complete darkness. This is why they seem to feel their way along the stream bed rather than search randomly.
• When a crayfish loses a claw to a predator, it abandons the fight and sprints backward using its tail like a jet engine, reaching speeds of 2 metres per second. The lost claw keeps snapping at the attacker for up to an hour, buying escape time. A new claw grows back within 18 months.
• Signal crayfish introduced to Europe have decimated native crayfish populations by carrying a plague fungus they're immune to. Researchers watched a single escaped aquarium specimen colonise 500 square kilometres of Scottish rivers in 15 years, wiping out populations that had thrived for centuries. They're now considered one of Europe's worst invasive species.
• A male crayfish performs an elaborate courtship dance involving precise body flicks and antenna brushing that lasts up to 40 minutes — all to convince a female not to attack him with her claws. If she rejects him, he retreats. If she accepts, they mate tail-to-tail while standing on their heads.
• Crayfish can live for 15 to 20 years in clean water, making them older than most dogs and many cats. They grow by shedding their entire armour-like shell up to 25 times in their lifetime, a process so violent it sometimes kills them. Each moult leaves them soft and defenceless for 24 hours.

At a glance

About the American Signal Crayfish

In the sun-dappled streams and rivers of North America, the American Signal Crayfish navigates its domain with deliberate, sideways grace, its vibrant blue claws snapping softly as it probes the shadows for unsuspecting morsels. With eyes that swivel independently, this diminutive crustacean surveys its surroundings with an air of quiet confidence, its very presence a testament to the intricate web of life that binds these freshwater ecosystems together. As it moves through the water, its signal flag - a vibrant blue spot on its claw - flashes like a tiny beacon, a striking advertisement of its identity in this hidden world.

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