Battle of the Bats

Mar 7, 2023

The Battle of Trafalgar is widely acclaimed as one the greatest sea battles of all time and the victor, the British admiral Lord Nelson, as one of the great warrior heroes of history.

It was a truly spectacular victory against the odds, with twenty-two French and Spanish ships captured or destroyed, over four thousand men killed, and ten thousand wounded or taken prisoner.  The British lost just over four hundred British seamen and not a single ship.

This was put down to the genius of Nelson and the fighting prowess of his officers and men. But there was another factor which has largely been overlooked by historians.  This is the contribution made by a species of flying mammal known as Chiroptera—or more commonly, the bat.

I stumbled on this startling piece of information when I was researching the story behind the battle for the latest novel in the Nathan Peake series—Trafalgar: The Fog of War.

One of the enduring mysteries of the battle was how Nelson’s fleet was able to advance head on for over half an hour across a mile or so of open sea exposed to the massed broadsides of over a thousand French and Spanish cannon without reply and without suffering any significant damage to ships or men.

This becomes even more astonishing when you consider that there was very little wind and that the disposition of the guns—almost all the guns were mounted on the sides of the ships and were unable to fire forward—meant that the British could not return fire until they broke through the enemy line.

It was noted at the time, by both sides, that the French and Spanish gunnery was incredibly poor.  The explanation given by the British was that the enemy spent so much time in port, their gunners couldn’t practice at firing from the rolling deck of a ship at sea.  They invariably fired high and wide, or their shot went straight into the water.

But most of the French and Spanish ships engaged at Trafalgar had spent more than three months at sea, voyaging to the West Indies and back in the bid to lure Nelson into following them, and from all accounts they had plenty of practice at the guns.

A much more convincing explanation lies in the quality of the gunpowder.

Gunpowder in those days was made from mixing sulphur, charcoal and saltpetre—otherwise known as potassium nitrate.  And the saltpetre was derived almost exclusively from the urine and excrement of bats.  Specially, bats in South America and India.

This guano, as it is known, was harvested from remote caves in the two sub-continents where the bats literally hung out in their millions.  It was then transported thousands of miles to Europe.  However, during the Revolutionary and Napoleonic wars the British command of the seas meant that this resource was largely denied to the French and their continental allies.

The French became so desperate for saltpetre they began to scrape it from the floors and walls of cellars and urinals where French men were accustomed to relieving themselves.  But the gunpowder was of very poor quality.  The French authorities blamed this on the increasing fashion for mixing wine with water.

I first heard this theory when I was involved as a director and producer in making a film about Trafalgar for Channel Four and interviewed a number of experts on the battle.  To begin with I have to admit I was sceptical. For one thing, Napoleon didn’t seem to have any trouble with his field artillery which was the prime factor in most of his victories on land.  I guess he could have kept the best gunpowder for the army, and the navy had to make do with whatever they could get, but I just couldn’t believe they couldn’t get all the saltpetre they needed from their own bats.  However, I was told that when it comes to making gunpowder, the urine of European bats just isn’t anything like as good as that of bats in the tropics.  Perhaps because the fruit and insects available to them is much higher in potassium nitrate.

I had the opportunity to test this out for myself when I visited the islands of Bocas del Torro off Panama where there is a famous bat cave that was used back in the day for the harvest of saltpetre.

During daylight hours the bats hang from the roof of the cave and come out at dusk to feed. When I went in, I could see what appeared to be hundreds and thousands of them hanging upside down from the roof, as bats do.  By then I was wading through water and after a hundred metres or so it was up to my chest.

I didn’t have any special equipment—I was wearing shorts and a t-shirt and I could only see them from the flashlight on my phone.  I couldn’t see any guano, though, waiting to be scraped off the walls of the cave. But maybe this was because the bats were relieving themselves directly into the water—and on anyone foolish enough to be wading through it of course.

I’d never really given much thought to how bats relieve themselves when they’re hanging upside down—I mean, they obviously don’t want it dribbling down into their faces any more than you or I would. Well, what they do is they start to swing backwards and forward until they get up a decent momentum and then they let it go. I could see it in the light of my phone, curving out in an arc and then falling into the stream—and quite a lot of the time on me.

By now I was literally up to my neck in water and the roof of the cave had got lower and lower so that the bats were just above my head. I was worried I might disturb them and they’d take off and start flying around.  I mean, there were thousands of them. But then I started to feel this stinging sensation in my legs and my groin, which worried me a lot more. I realised it must be the potassium nitrate. It soon spread all over my body, right up to my neck. Fortunately, the water level started to go down and I could see light at the end of the tunnel. When I finally got out I could hear the sea, so I found some soap in my rucksack and plunged in.  I read later that apart from irritating the skin and the eyes, potassium nitrate can interfere with the ability of the blood to carry oxygen, which causes headaches, dizziness and exhaustion, and the lips and skin to turn blue.

Maybe the salt water neutralised it because as far as I know my visit to the bat cave has had no lasting effect.  But now I could understand why the South American bats were such good providers of saltpetre for the British Navy.

And that, in a nutshell, is how bats helped win the Battle of Trafalgar.