I have heard all the various theories concerning zebra stripes over the years, and my inclination is that several could be true at the same time, as you pointed out. Insect repellant, dazzling predators, allowing foals to identify mum’s uniquely striped bum. In any case, wearing dark blue or black clothing when touring in tsetse fly areas is a certain way to attract those pesky beasts, so I wonder…
As much of a blessing as the internet is, in these days of easy access to information, it’s hard to tell what is factual and what is complete fabrication. Thankfully serious scientific papers, accredited books, and generally authors who want to be taken seriously won’t cite internet sources as references.
However, the speed at which one can disseminate information across the internet often means that the first inkling we have of a scientific breakthrough is web-based. Or at least through twitter or some-other social media platform. Someone catches wind of something, posts about it, and the information goes viral in the blink of an eye. It can take months after the initial announcement for the real scientific evidence to be published and become readily available.
The above introduction is really an attempt to cover myself here, as the information discussed below was certainly not gleaned from any scientific paper. It was from a random tweet that was shown to me by one of the camp managers, which, if true, goes a long way to answering one of the age-old questions of the African Bush: why do zebras have stripes?
We’ve covered this topic a couple of times over the years, but any discussion of the matter generally just involves a recitation of a number of theories. This tweet (see picture below), if true, might go a long way towards answering the question, while – of course – posing many new ones.
Funny picture, right?
Well, according to the tweet (I eventually found the article after initially typing this), scientists in Japan apparently found that painting cows in zebra stripes dramatically reduced the number of insects that were biting them, by roughly 50%!
If this is really the case (it’s not always that simple, as evolutionary features like this often have multiple benefits, and therefore evolved for multiple reasons), it will make the task of guides a whole lot easier in future, as an extensive discussion about the stripe evolution won’t be necessary.
Or will it?
The issue now – at least for me – is why didn’t other animals evolve similar anti-fly mechanisms?
I don’t know how many of you have been bitten by a Tsetse fly, but it’s unpleasant, to say the least. It’s very similar to a horse-fly bite, except the horrible little buggers can’t be killed! You’ll swat one as you’ll swat a normal fly, and it will drop to the ground, seemingly on its way to fly Heaven, but give it a minute or two and it will be buzzing around again, looking for any exposed areas of skin you may have. Fortunately there are no Tsetse flies at Londolozi, but having travelled further north in Tsetse country, I can emphatically agree with zebras that evolving a mechanism to defend against them would certainly be in one’s best interest.
But why would wildebeest not develop stripes to defend against them? Or Thomson’s gazelles, or giraffe?
I don’t know.
Maybe zebras emit a different pheromone type that is more attractive to the Tsetses, or biting insects in general (the tweet didn’t focus specifically on Tsetses, I’m just taking the opportunity to vent my dislike for them). Perhaps there was some sort of specific habitat co-existence between the equines and the insects in some long-forgotten time. Maybe the nagana – a type of disease that can kill horses and cattle with ease, and essentially left vast tracts of Africa unexplored because early settlers couldn’t venture into the interior as they were almost guaranteed to lose their valuable herds – affected Zebras the worst, so it was imperative that over time they developed some extra barrier against transmission.
Herein lies the rub (and the appeal), in that with every question answered, 10 more get asked.
We could sprout theories here about why stripes are unique to zebras until the cows come home, and why do different zebra species have different strip densities, but I’d rather close off here.
As I said earlier, I’ve only read an article that discusses the cow-painting experiment; I’ve yet to read a scientific paper with anything conclusive.
Any thoughts on the matter…?
Filed under General Nature Wildlife
Interesting point Gawie.
It would be great to see the experiment repeated with a different type of paint…
The Japanese scientists actually considered the paint! They painted some cows just with entirely black stripes, and some cows with black and white stripes.
The black-striped cows had flies settle on them and bite them at the same rate as unstriped cows, whereas black and white stripes confuse flies. Interestingly, this only works up close. All of them attract flies from a distance, but fewer flies settle on stripes.
The U.K. experiment on horses tested 3 captive zebras vs. horses, and then also horses wearing white, black or striped coats. Again, flies approached them a similar amount, but they didn’t slow down near the zebras and striped coats. Basically they just bumped into the animal, then decided not to settle. The stripes seem to confuse them that the striped being is actually an object/animal.
Last, zebras react more than horses when they have a fly on them. They swish their tails, bite at the fly, and even run away. Horses don’t do that as much, which suggests zebras live in areas where it’s more important (from a disease point of view) that they don’t get bitten.