Why do zebras have stripes? They make bad landing strips for flies
By Will Dunham WASHINGTON (Reuters) - Scientists are providing new evidence to answer the longstanding question about why zebras have stripes. It appears stripes make terrible landing strips, bamboozling the fierce blood-sucking flies that try to feast on zebras and carry deadly diseases
By Will Dunham
WASHINGTON (Reuters) - Scientists are providing new evidence to answer the longstanding question about why zebras have stripes. It appears stripes make terrible landing strips, bamboozling the fierce blood-sucking flies that try to feast on zebras and carry deadly diseases.
Researchers on Wednesday described experiments demonstrating that horse flies have a difficult time landing on zebras while easily landing on uniformly coloured horses. In one experiment, the researchers put cloth coats bearing striped patterns on horses and observed that fewer flies landed on them than when the same horses wore single-colour coats.
"We showed that horse flies approach zebras and uniformly coloured horses at similar rates but that they fail to land on zebras - or striped horse coats - because they fail to decelerate properly, and so fly past them or literally bump into them and bounce off," said behavioural ecologist Tim Caro of the University of California-Davis, lead author of the research published in the journal PLOS ONE.
Close cousins to horses and donkeys, the world's three zebra species, known for their black-and-white striped bodies, roam Africa's savannas eating a variety of grasses. Their stripe patterns vary among individuals, with no two alike.
There had been four main hypotheses about the advantages zebras accrued by evolving stripes: camouflage to avoid large predators; a social function like individual recognition; thermoregulation, with stripes setting up convection currents along the animal's back; and thwarting biting fly attacks.
"Only the last stands up to scrutiny," Caro said. "Most biologists involved with research on mammal coloration accept that this is the reason that zebras have stripes."
African horse flies carry diseases such as trypanosomiasis and African horse sickness that cause wasting and can be fatal.
The researchers videoed horse flies as they tried to prey on captive zebras and domestic horses at a livery in North Somerset, England. Stripes did not deter flies from a distance, as they circled horses and zebras at similar rates. But the flies managed to land on zebras less than a quarter as often.
University of Bristol biologist and study co-author Martin How said stripes may dazzle flies somehow once the insects venture close enough to see them with their low-resolution eyes.
"In addition to stripes that prevent controlled landings by horse flies, zebras are constantly swishing their tail and may run off if horse flies do land successfully, so they are also using behavioural means to prevent flies probing for blood," Caro said.
(Reporting by Will Dunham; Editing by Sandra Maler)
This story has not been edited by Firstpost staff and is generated by auto-feed.
By Robin Emmott and John Irish | BRUSSELS/PARIS BRUSSELS/PARIS France and Germany will agree to a U.S. plan for NATO to take a bigger role in the fight against Islamic militants at a meeting with President Donald Trump on Thursday, but insist the move is purely symbolic, four senior European diplomats said.The decision to allow the North Atlantic Treaty Organization to join the coalition against Islamic State in Syria and Iraq follows weeks of pressure on the two allies, who are wary of NATO confronting Russia in Syria and of alienating Arab countries who see NATO as pushing a pro-Western agenda."NATO as an institution will join the coalition," said one senior diplomat involved in the discussions. "The question is whether this just a symbolic gesture to the United States
BEIJING Chinese President Xi Jinping on Wednesday called for greater efforts to make the country's navy a world class one, strong in operations on, below and above the surface, as it steps up its ability to project power far from its shores.China's navy has taken an increasingly prominent role in recent months, with a rising star admiral taking command, its first aircraft carrier sailing around self-ruled Taiwan and a new aircraft carrier launched last month.With President Donald Trump promising a US shipbuilding spree and unnerving Beijing with his unpredictable approach on hot button issues including Taiwan and the South and East China Seas, China is pushing to narrow the gap with the U.S. Navy.Inspecting navy headquarters, Xi said the navy should "aim for the top ranks in the world", the Defence Ministry said in a statement about his visit."Building a strong and modern navy is an important mark of a top ranking global military," the ministry paraphrased Xi as saying.