Why crocodiles attack human being

A new study reveals where and when crocodiles attack people, and advice on how to prevent it.

Stare into the jaws of a crocodile and it might be the last thing you will like to see. Their formidable jaws can snap bones like twigs.

Each time a crocodile attacks a person, the media paints a picture of fearsome aggressive beasts that reign terror on unsuspecting victims.

That they are dangerous is clear but like many things in nature, the story is more complicated.

Crocodiles do not necessarily set out to hunt humans. They are clearly ferocious hunters, but they are opportunistic predators. 

If you go splashing through a muddy river near the crocodile and it is hungry, it will come over and grab you. Any animal that moves is fair game. They will even venture onto land to find prey. If that warm blooded mammal happens to be a human, they will not discriminate. 

In Africa alone there are several hundred crocodile attacks on humans per year. Many take place in small communities and are not widely reported; between a third to half are fatal, depending on the species.

They are far more common than shark attacks and yet do not receive as much media coverage. 

Shark attacks tend to be more frequent in richer countries, says Simon Pooley of Imperial College London, UK, who studies the history and challenges of crocodile conservation efforts.

Pooley grew up with crocodiles. He experienced the devastation they can cause families first hand. Many people depend on rivers for their livelihood and so avoiding the water is not always an option. 

He has now looked at the patterns surrounding 65 years of crocodile attacks in southern Africa to discover when they are most likely to occur and who is most at risk.

Crocodile

His team has also created a booklet, which is now being distributed to areas where such attacks frequently occur. "It seemed strange that we weren't using this kind of historical data to try and save human and crocodile lives in these large areas of the world where attacks take place," he says.

Attacks are often seasonal. They are most prevalent between October and March. They often occur during rainfall, temperature increases and the breeding season.

It's not immediately clear why some of these patterns exist. That crocodiles attack when it's warmer is thought to be because they are ectothermic (cold blooded) creatures. That is, they depend on the sun's heat for energy. This means they will hunt more when it's warmer. When it's colder they are not as active. 

Every attack Pooley studied occurred when the minimum temperature was higher than usual. Divers in crocodile-rich rivers are said to restrict their diving to when it's under 19 degrees Celsius. "If it's colder it's regarded as safe, if it's warmer they don’t get in the water," says Pooley.

From the records, Pooley found that most attacks took place while people were swimming; boys were attacked most often. This makes sense as smaller prey is easier to kill. The mortality rate for children is much higher than for adults.

Men that were attacked were often fishing, while women were crossing rivers or doing domestic chores.

Attacks are usually feeding related, Pooley says. "If you go splashing through a muddy river near the crocodile and it's hungry, it will come over and grab you."

That's why it's important to stay at least three metres from the edge of water. People should not assume that just because they can't see a crocodile that it's not there; crocodiles can stay underwater for over an hour.

Furthermore, if you do need to cross the water in a big group, it is not wise to splash around in the water or create lots of noise.

It may seem obvious to avoid attracting their attention, but people have been told that making lots of noise might scare them away. This is terrible advice, Pooley says.  

Of course, if you do get grabbed by a crocodile there's not much to be done. You can try and put your fingers in its eyes or hit it on the nose, as both are sensitive areas. If you have something to hand to put down its throat, it might cause it to gag and release you.

These are the worst case scenarios. Nile and salt water crocodiles are the most dangerous. Not all species attack humans. Many are wary of people and may only bite if they are disturbed or taken by surprise.

Pooley hopes more attacks can be prevented if people are made aware of the specific risks that face them.

Crocodiles are killed in an attempt to find remains of missing children in their stomachs

At the same time, the crocodiles that attack humans are also in need of protecting. The Nile crocodile, mostly found in Africa, is abundant across the continent but other species such as the Philippine and Orinoco crocodiles are listed as critically endangered.

They are at risk precisely because they are dangerous. This can be a difficult message to get across. It is hard to conserve an animal that people hunt in an attempt to curb future attacks.   

Revenge attacks are also common. Late last year a woman and her unborn child were killed in Uganda, Africa. Her husband sought revenge and killed the crocodile in question one month later. He used a spear crafted by a local blacksmith. 

In January 2014, after a boy went missing from a suspected crocodile attack, authorities in Australia issued a shoot-to-kill order on any crocodile bigger than two metres. Three were killed by local police. The boy's remains were later discovered near to where the attack took place. After the incident there were calls to cull more crocodiles.

They can be hunted for game too. In March 2015, a policeman in Mexico was suspended after he was filmed shooting a helpless crocodile with a machine gun.

These are but some of the issues facing crocodiles. Habitat destruction is also a threat. Telling people about such issues is known to be ineffective. Helping locals to stay safer would better deter potential eradication demands, says Pooley.

Crocodiles and humans may never coexist completely peacefully, but knowing more about how to avoid being a crocodile's dinner is an important first step.

Presented by Melissa Hogenboom