We know that many of the traits we see in animals are there because they have evolved by being somehow useful to the species. But evolution is chaotic and the supposed benefits of strange functions are not always obvious. Take for example zebra crossing.
The black and white robes of the three zebra species that roam Africa have been a biological puzzle for decades, with several competing hypotheses. Now the researchers have added a new data point – and all it took was dressing with some horses.
Okay, there was more science than that. However, the team's results showed that the stripes somehow prevent the landing and keep zebras relatively safe from the annoying insect bites.
It's not a new idea. Scientists have known for years that fewer flies land on zebras. In fact, a 201
We still are not sure which mechanism is accurate, but scientists from the US and UK have limited it. They have discovered that flies land on horses more than three times as often as they land on zebras because the stripes appear to confuse the insects and affect their ability to control their flight.
The team spent several hours recording horses and zebras, the number of blood-sucking horseflies (Tabanids) that swarm around, approaching and landing on the animals.
To make sure that there is nothing inherent in the zebra air or the movement that changes the flight behavior, they disguise themselves to exclude these variables (zebrables, if you will).
To do this The team dressed horses in coats – all black, all white and black and white striped – and recorded the flight activity again. They also took videos of horses and zebras to do a detailed analysis of what the flies actually do. and observe the behaviors of both species in response to flies.
They found that about the same number of flies lay around both animals and approach zebras as often as horses. But if you fly to a striped coat? Then it goes a bit wrong.
"We have noticed that tabanids approaching zebras slow down unchecked towards the end of their trajectory, slowing down steadily before landing or touching horsemeat," the researchers write in their newspaper
. " Flies often simply hit zebras, but they do not land or fly away. "
Interestingly, the flies still landed on the horse's exposed head as often as usual – suggesting that the mantle had an effect.
And that's not all. When the flies landed successfully, they did not stay on zebra for so long. The videos, which recorded the response of the animals to flies, showed that zebras are more active than horses running away from the tails and fleeing.
All in all, the reduced time for zebras meant that the flies did not bite or eat them. As in horses, it can be seen that the stripes actually play a role here.
It is of course possible that the strips fulfill several functions. Studies to date seem to rule out environmental camouflage, social interaction and thermoregulation, but there is still the possibility that the stripes confuse predators by creating a kind of "dazzling" effect as a kind of movement staring that makes it difficult to distinguish individuals in an environment packed herd.
But the evidence here suggests that one of the benefits of streaking is increased protection against biting flies.
We wonder if this is the last time we will know about it.
The team's research was published in the journal PLOS One .