(Phys.org)—A pair of researchers
with the Indian Institute of Science Education and Research Thiruvananthapuram
has found that stripes on lizards cause predators to see them as moving slower
than they actually are, causing attackers to miss their targets. In their paper
published in the journal Royal Society Open Science, Gopal Murali and
Ullasa Kodandaramaiah discuss their theories on why some animals have stripes,
their experiments with grad students playing specially designed computer games
and what they found as a result.
Many people have wondered over
many years why it is that some animals have stripes—some have suggested they
serve as camouflage, while others have theorized that the patterns cause
confusion in the eyes of predators—stripes on zebras, for example, might
perhaps cause lions to have trouble fixating on just one member of a herd. In
this new effort, the research pair focused specifically on lizards, but rather than use live
ones, they created virtual ones on computer screens. And rather than use real
predators, they used grad students who were asked to "catch" the
lizards, by simply clicking on their bodies. But, there was a catch, some of
the lizards had stripes on their bodies similar to those on real lizards, while
others had stripes only on their tales. In analyzing the results of play, the
researchers found that the grad students were 25 percent less accurate in
clicking on the bodies of the lizards when the body was striped.
In another test, the researchers
asked the student volunteers to simply report which of two lizards on a
computer screen was moving faster than the other. In this test, some of the
lizards had stripes while others were spotted. If a volunteer reported that one
was faster than the other, than the speed of that lizard was slowed down al
little bit—this routine continued until the volunteer reported that the lizards
were moving at the same speed. In analyzing the results of multiple tests with
multiple volunteers, the researchers found that the striped lizards were
actually moving 5 percent faster on average than the spotted lizards at the end
of the game.
The researchers suggest their
experiments show that stripes on lizards in the real world might cause
predators to misjudge the speed of their prey, leaving them grabbing a tail
that simply falls away as the lizard escapes.
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