Why does the zebra have stripes?
While procrastinating on this lovely Sunday afternoon, I stumbled across this incredible video of a octopus camouflage in action:
Now, we don’t have anything quite that camouflaged in the Serengeti, but in watching that video my thoughts turned to one of our more strikingly colored species: the zebra. Their starkly contrasting black and white stripes have puzzled researchers and naturalists for a long time.
For starters, the stripes seem like they would be terrible camouflage. I mean, how much more could you stand out from the open plains of waving gold grass? But at dawn and dusk, especially from a distance, the stripes seem to bleed into gray, making them look a surprising lot like elephants (no joke), or rocks, or even nothing at all. Still, up close they still look like bright black-on-white zebras, and it’s hard to imagine that any lion lurking in the thickets nearby would be fooled.
Some researchers have mused that the bold patterns disrupt the perception of predators, and that when the zebras run en masse from an attacking lion, they become a confusing jumble of stripes into which the initial target disappears. Others have pointed out that every zebra has a unique set of stripes, and that these stocky equids might use these patterns to identify herd members, mates, or even mothers (if you’re a hungry foal).
One of the my favorite explanations has always been that the stripes protect against the savanna’s most fearsome creature: the tsetse fly. These blood-sucking insects are not only vectors for some nasty diseases (such as sleeping sickness), but also hurt. A lot. (Having spent more time than I care to remember in the woodlands where these terrible, terrible creatures thrive, just the thought of tsetses makes me shudder. I have spent many hours hurling expletives (fruitlessly) at the tiny terrors.) Tsetse flies suck. A lot. And if wearing stripes were a way to fend them off, I’d have gone out in a zebra suit every day. There are in fact stories of one intrepid researcher back in the day dressing up in a stripey suit and attempting to test whether zebra stripes deter tsetses. But there’s only so much that one man in a zebra outfit can do, and field experiments are notoriously difficult…and so this remained a buried rumor until last year.
Last year, Swedish researchers discovered that horseflies (a close cousin to the terrible tsetse) don’t like stripes. And they tested this on an experiment useing number of fake, plastic zebras painted solid black, solid white, and various things in between. Turns out that the flies really like dark colors over light colors, but still like solid light colors over stripes. And while in the real world, there are things (such as smells) that may attract tsetses to stripey animals despite their off-putting pattern, this study is pretty exciting. And next time I have to venture into the savannah woodlands? You can bet I’m wearing that zebra-striped shirt.