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.
Zebras |
Researchers on Wednesday described experiments demonstrating that
horse flies have a difficult time landing on zebras while easily landing
on uniformly colored 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-color coats.
“We showed that horse flies approach zebras and uniformly colored
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.
Breeding high performance bugs for animal feed.
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.
NAN
No comments:
Post a Comment