Killer dolphins? Exploding bats? What animals are used by militaries and why?

Dogs, pigs and even bats have been pressed into service, sometimes as part of unusual experiments.

Dolphins capable of finding sea mines, dogs capable of exploding tanks and bats fitted with incendiary bombs.

The military has always had a close bond with animals, but does that go beyond sniffer dogs and ceremonial horses?

Well, in some cases, yes.

Rumours of trained killer dolphins may be wide of the mark, but the US does have a Mark 7 Marine Mammal System, better known as a bottlenose dolphin, to detect sea mines.

And, rather less surprisingly, military dogs were used to sniff out explosives in Afghanistan.

Why has technology not replaced them?

Gervase Phillips, a lecturer in history, politics and philosophy at Manchester Metropolitan University, told Forces News it is because they are too good at what they do.

"We have nothing like a dog's nose to smell explosives yet and nothing as good at finding things on the seabed as a dolphin or a sea lion," he said.

"There are all kinds of those military roles for which, unfortunately, we have no practical alternative."

Watch: US military mine-hunting dolphins and life-saving sealions.

Dogs have been fighting alongside humans for much of history, with guarding and hunting down the enemy their earliest job.

But as this film from the US Army in the Second World War shows, their adaptability was soon put to good use, with dogs trained to take ammunition back to the frontline.

It is even rumoured that the Japanese deployed bomb dogs to run in among the enemy and then detonate, and the USSR tried to train dogs to blow up tanks.

"I think the Russian use of dogs packed with explosives during World War Two is documented, as far as I'm aware," Mr Phillips said. 

"My understanding was it was unsuccessful, that they associated the bottom of tanks with food, but they weren't discriminating about whose tank it was.

"My sense is, where these experiments have been tried, they have not been successful," he added.

Watch: Meet the MOD police dogs sniffing out crime for UK defence.

Another rumour was of a trial of bats fitted with incendiary bombs.

Fact or fiction, it's never been tried again. 

Pigeons, on the other hand, have served the military and were vital for the British in the First World War getting messages back from the front. 

And 200,000 of the birds were put to work in the Second World War, with pigeons having even won the prestigious Dickin medal, often dubbed the animal Victoria Cross, for their war service. 

But it's the dog that has shown it has the longevity to still be vital to militaries across the world, guarding, defending and sniffing out danger.

They likely win the plaudit of being the military man and woman's best friend.