The largest live crocodile ever measured was 20.3 feet long and found right here in Australia’s Northern Territory. After decades of merciless hunting, Australia’s crocodile population dropped to 3,000 in the 1970s. Thanks to a hunting ban, populations have since rebounded. Today, 140,000 saltwater crocs are estimated to live in Australia, with 80,000 in the Northern Territory alone.
A big one patrols the dam up the road from where we were studying cane toads (left). We had no desire to cross his path. Instead, we stopped by Crocosaurus Cove in downtown Darwin to meet “Chopper”—a 1,750-pound adult male—and learn more about these amazing creatures.
What is a Crocodile Exactly?
The word crocodile comes from the Greek word krokodeilos—meaning “pebble worm.” Alligator, on the other hand, comes from the Spanish word for lizard: el lagarto. Neither name is very accurate. Crocodiles are reptiles, but they’re not lizards. And although they’re not technically dinosaurs, the two share a common ancestor: birds.
Like birds, female crocs lay eggs. And after guarding their nests for 2-3 months, female crocs will help their babies hatch. They’ve even been seen feeding pieces of meat to their hatchlings—just like mama birds!
Crocs are highly-social animals. They live in groups and establish territories. Usually they can settle territorial disputes through growls and groans, but if all else fails, violent fights can break out. The staff at Crocosaurus Cove believe Chopper lost his two front feet (below) in territorial battles with younger crocs in the wild. At 80 years old, he was getting too old to fight them off.
Crocs are very intelligent, too. They have the most advanced brain of all reptiles. Being smart means they can learn routines like seasonal migrations and when and where animals come to the river to drink. This allows them to predict the best time and place to catch a meal.
Crocs are stealth hunters. Rather than waste energy chasing prey, crocs will wait for food to come to them and then STRIKE like an uncoiled spring. Did you know crocs can literally jump out of the water? They use their powerful tails to swim upward at speed and then launch their bodies out to nab birds flying across the water’s surface.
We hear stories of crocs taking down zebra, cattle, and kangaroos, but those big animals are rare feasts. More commonly, their diet consists of smaller prey like fish, crabs, and snails. Juveniles dine off a kids’ menu of insects, shrimp, frogs, and fish. But no cane toads!
Because large crocodiles have such a massive bite—like a 3.5 ton truck falling on your foot—their teeth don’t need to be sharp to punch through skin and bone. Each tooth is hollow at the base, so when the old one breaks off, there’s a new one to replace it immediately.
To hunt in murky water, crocs have excellent hearing and an excellent sense of smell. But they also have a sixth sense. Each scale of a saltwater crocodile’s skin has tiny, black dots on it. These “dermal pressure receptors” detect minute pressure changes in the water, such that the croc can tell if a fish is swimming past even if it can’t see it.
Life underwater means going without oxygen. To survive, crocs evolved with special superpowers.
When they dive, their ear flaps and nostrils seal off; a third eyelid covers the eye; and the valve at the back of the tongue closes to keep water out of the throat. A croc’s four-chambered heart—the most advanced in the animal kingdom—contains two valves to redirect blood to the brain and other essential organs. If a crocodile wants to stay underwater for an extended period, it can slow its heart rate to less than 5 beats per minute and then switch back instantly to STRIKE!
Even crocodile blood is super-powered. All vertebrates, including humans, have a special protein in their red blood cells called “hemoglobin” that transports oxygen from our lungs to the rest of our body. Crocodile hemoglobin is like a Boeing 747 Dreamlifter; it can carry more oxygen than any other animal. In fact, researchers have been able to use this oxygen-rich croc blood to help human beings survive dangerous and complicated heart transplants.
See, humans and crocs can live together after all!