Bull Shark Shark Bites

My name's Steve Backshall.

Self-confessed shark-obsessed.

This is Shark Bites.

This time, we meet a shark considered the most

menacing of all - the bull shark.

These stocky and pugnacious predators probably have

the worst reputation of all sharks,

but there's more to these bruisers than meets the eye.

They like to hunt in warm coastal waters,

but the bull shark has another killer credential - they can

live in fresh water and have been found 4,000km up the Amazon River.

So how can a shark that evolved to live in salt water

also travel into fresh water?

Mexico's coast is the perfect place to see these feisty fish.

This is the bull shark's ocean home,

and it wasn't long before they came to check us out.

And our first bull shark is coming in towards us right now.

Look at this!

In open clear water, these sharks are not going to attack.

But that doesn't stop my heart from racing.

There must be 10 or 15 of them around us at the moment,

all circling us with real intent.

Look at these three! Such dramatic animals!

Whoa!

There's no doubt - approaching dusk,

these animals have a totally different attitude about them.

It's clear that now they're ready to start hunting.

But to satisfy their appetite,

these hungry hunters also head inland to find more prey.

And how they do that is down to some ingenious bull shark biology.

One of the ways a bull shark will absorb water

and vital salts is through its skin.

But living in both freshwater and saltwater environments,

the concentrations of salt are always changing,

so the bull shark needs to adapt.

Fortunately, they have very clever kidneys.

When they're in the ocean, they need to get rid of excess salt but

when they move into a freshwater environment,

like a lake or a river, they do just the opposite.

The kidneys hang on to the salts they need to survive

and get rid of extra water.

These sharks have the best of both worlds.

Surviving in fresh water and salt water means

they have access to even more prey - their very own bull shark buffet.

The bull shark - seriously adaptable with a bullish attitude, it is

a highly honed hunter, making it the most menacing shark of all.