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Killer crocodiles’ deadly anatomy
They outlived the dinosaurs, but these hunters are anything but elderly
Crocodiles are often described as living fossils, but despite the fact that their body shape hasn’t changed much in the last 200 million years, they are actually some of the most sophisticated reptiles on Earth. Like all living reptiles they are cold-blooded, but that doesn’t make them sluggish. Crocodiles have a four-chambered heart and muscles that mimic our diaphragm to ensure they can quickly pump oxygen around their bodies for explosive bursts of speed. Crocodiles are ambush predators; their preferred tactic is to lurk in the river with just their eyes and nostrils visible above the surface and burst out of the water to surprise animals that have come to the bank to drink. If their initial lunge fails, they can chase prey over land at speeds of 17 kilometres per hour. The galloping gait of the crocodile was dismissed as a folk legend for many years, simply because hardly anyone who witnessed it lived to tell the tale.
Once a crocodile has grabbed its prey, it will drag it into the water and pull it under. Crocodiles need air to breathe, but they can hold their breath for around an hour, and drowning prey is easier and more reliable than risking it escaping if they unclamp their mighty jaws. Crocodile teeth are only designed for gripping and puncturing; they have no incisors or carnassials to slice meat off a carcass. Instead they will grip a chunk of flesh with the front teeth and spin violently on their long axis to twist off a bite-sized piece. Crocodiles also don’t have lips, so they can’t seal their mouth shut when eating. This means they can’t swallow food underwater without drowning themselves, meaning each torn-off mouthful has to be brought to the surface and tossed into the back of the mouth.
When food is scarce, their coldblooded metabolism allows crocodiles to go for as long as two years without eating at all. This, combined with their ability to scavenge rotting meat, was probably what allowed them to survive the event that killed the dinosaurs.