Imagine you’re an aquatic mammal, searching for prey buried in the mud of a stream. You close your eyes, ears and nose, dive underwater, swim down to the bottom, and then what? This is how the platypus hunts. Blind, deaf, and unable to smell anything, it pays attention to something else. Shrimp and other prey are moving around, and each bit of movement could give their position away. All muscle contractions involve electric pulses, and because water conducts electricity those pulses are broadcast out.

The secret weapon of the platypus is its beak, which is covered in mucus glands capable of  sensing electric fields. Each gland has nerves and the mucus transmits the electricity to the nerves. It’s a fearsome arsenal of sensors – each platypus has an estimated 40,000 electro-sensors. It’s also got 60,000 touch sensors on its beak, and it uses the two systems together to search for objects in the mud and then decide whether it might be suitable for dinner.

As the platypus swims along, it sweeps its bill from side to side, and it uses the changing signal from each sweep to work out the direction of the prey. Not only will they swim straight towards a shrimp, they’ll quickly home in on the DC voltage from a buried battery as well. This is highly effective hunting – a platypus finds half its body weight in prey every single night.

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