Even if they can't see, hear, or smell you, they have what are called dermal pressure sensors, which are on every scale of the body – there are hundreds on the head – and are about the size of a pinhead. They can sense vibrations through those. It's believed they can feel a heartbeat in the water up to 1km away.
As they grow, they move on to larger prey—dogs, pigs, people, horses and buffalo. Our species fits comfortably in their diet, slipping into the line-up between pigs and horses. Crocodiles may be opportunistic hunters, but their encounters with prey aren't chance. They think about it.
They have a right aorta that comes out of the left ventricle and a left aorta from the right ventricle. Adding to the anatomical complexity is a valve found at the top of the right ventricle that looks like a pair of cog-teeth, which the animals can actively control to redirect the flow of blood.
But crocodile (and alligator) hearts have an extra valve that mammal and bird hearts don't have. The extra valve is a flap that the animal can close in order to keep blood from flowing toward the lungs.
How Long? In general, crocodilians seem to prefer to get around 17 hours of sleep per day.
Crocodiles in captivity have been known to reach 100 years old. What's most interesting about crocodiles is that they don't die of old age. They do not die from biological aging. Instead, they continue to grow and grow until some external factor causes them to die.
In the wild, an older, weaker croc is more likely to face starvation or competition, but even in captivity, the animals inevitably die.
"If they've got hold of you, poking the eyes is the only possible way you can fight back - they have thousands of years of instinct telling them this is the only vulnerable part of their body and they need to let go," Mr Cooper says.
In rare cases, individual crocodilians have been known to bond so strongly with people that they become playmates for years. For example, a man who rescued a crocodile that had been shot in the head became close friends with the animal.
A struggling crocodile underwater can actually drown in 20 to 30 minutes, as some people attempting to capture crocodiles have found to their cost. The smaller the crocodile, the lower its capacity to survive without oxygen underwater. In times of extreme stress, extended dives can be employed by the crocodile.
"Saltwater crocs have the strongest recorded bite force of any animal on the planet — [the] kind of force can easily crush a human skull," Frost said.
Their armor-like skin is near impenetrable—no amount of kicking, punching, or other fighting can pierce it—and their heads are solid masses of bone. According to Chris Packham, wildlife presenter and crocodile fan, “there are no weak points” across their bodies So what do you do?
An average crocodile that weighs 700 pounds and measures over 10 feet long is going to be too powerful for a human to overcome.
If a crocodile heads your way, run away in a straight line. The myth about moving in a zig-zag motion is just that—a myth. Crocodiles can move at 10 miles per hour, so remove those flip flops so you can run faster.
There are a couple of reasons why swimming with sharks is safer. Most sharks do not like the way people taste. They expect their prey to taste a certain way, like fish/seal, and we do not taste like that. Sharks also do not like the sensation of eating people.
But how quickly can they run? Most crocodiles can achieve speeds of around 12 to 14 kph for short periods, which is somewhat slower than a fit human can run. Don't believe the hype - if you're reasonably fit, you can definitely outrun a crocodile!
All crocodiles have rather keen hearing and have an external ear made up of a short tube closed by a strong valvular flap that ends at the tympanum. The American alligator (Alligator mississippiensis) can hear sounds within a range of 50 to 4,000 hertz.
"All crocodiles bite, from hatchling to adult," Ms Plume said. "Some can be more aggressive than others but all should be treated with respect and caution. "A bite from a hatchling for an adult is more of a shock than it is painful, however a 70-centimetre animal can give quite a nasty bite."
Yet, despite this aggressiveness, crocodiles are also affectionate animals and often attempt to show their warmth through touches during mating. A male crocodile will rub against the female, "to see if she will return the affection or not" ("Crocodile").
BRAWNY BITE.
According to Irwin, parrots and similar birds, like this sulfur-crested cockatoo, are the animals that he fears most.
A hippo would win a fight against a crocodile. Although crocodiles are large, powerful creatures, they cannot kill a fully grown hippo. Hippos are large, roundish animals that are much taller than crocodiles. The only place they would be vulnerable to attack is their legs.
Attempt to gouge, kick, or poke the animal in the eye with your hands or whatever you can grab. Don't give up until you are free, you are literally fighting for your life. Attack the animal's head. If you land as many blows as possible on the animal's head, you stand a higher chance that it will let go.
To date, there's only one species that has been called 'biologically immortal': the jellyfish Turritopsis dohrnii. These small, transparent animals hang out in oceans around the world and can turn back time by reverting to an earlier stage of their life cycle.
There are two main reasons. First, crocodiles can live for a very long time without food. Second, they lived in places that were the least affected when the asteroid hit Earth.
Background on crocodiles
The oldest crocodile on record was estimated to be 140 years old! Crocodiles are often confused with other members of their order, although they can be broken up into three distinct families.