10 | SCIENCE NEWS | May 21, 2011 www.sciencenews.orgEyespot deficitsstymie peacocks
Females appear to require a
minimum number of flecks
By Susan Milius
The tale of how the peacock got his eyespots has taken a new turn.
His shimmering train of feathers tippedwith eye-shaped spots ranks among themost cited examples of what Darwincalled sexual selection. In this singles barapproach to evolution, flashy plumage andother ornaments arise not because theyenhance survival of the fittest but becausethey favor reproduction of the sexiest.
Basic principles aren’t in doubt for thepeacock exemplar. Yet “everybody usesit without knowing much about how itworks,” says Roslyn Dakin of Queen’sUniversity in Kingston, Canada.
She found that a train with especiallyhigh numbers of eyespots did not seemto improve a male’s chances of dazzling afemale into mating — but having too fewspots was definitely a hindrance.
That flies in the face of classic experi-
ments on peacock courtship, Dakin and
Robert Montgomerie, also of Queen’s,
acknowledge in an upcoming Animal
Behaviour. But they also report addi-
tional work suggesting a new explana-
tion for why peahens sometimes don’t
appear to care about eyespot number.
Eyespots seemed a good predictor of amale’s chances of success in past studiesof peafowl in England. A female cruising among males routinely picked theone who showed her the most eyespots,says pioneer of peacock science MarionPetrie of Newcastle University inEngland. Snipping 20 feather tips out ofmales’ trains lowered courtship success.
But feathers ruffled in 2008, whenJapanese researchers studying feralpeacocks reported finding no courtshipadvantage for eyespot number in sevenyears of data.
Dakin and Montgomerie have nowstudied the issue in two peafowl populations in Canada and one in the UnitedStates. Dakin repeated part of Petrie’seyespot-snipping experiment. As predicted, males deprived of 20 of theireyespots — leaving fewer than 138 in thedisplays — managed to mate fewer timesoverall than fully eyespotted males.
When Dakin and Montgomerie
pooled their eyespot data with other
published reports, eyespot effects didn’t
show up among 102 peacocks for the top
75 percent of trains ranked by spot num-
ber. Yet the most eyespot-challenged
birds, flashing spot numbers only in the
120s and 130s, rarely had any mating
success at all. “It certainly looks like a
threshold,” Dakin says.
The threshold idea makes sense at firstglance, says Adeline Loyau, a peacockresearcher at the CNRS research stationin Moulis, France. The struggle to understand the long-familiar peacock, she adds,“suggests that we are still far from unraveling the mechanisms of mate choice.” s
Life For longer versions of these and other Life stories, visit www.sciencenews.orgBy Rachel Ehrenberg
Inspired by a caterpillar thatmakes like a wheel and rollsaway from predators, researchers have created a robot thatcurls itself into a loop and peelsout at speeds faster than a halfmeter per second.
Called GoQBot, the 10-centimeter-long robot has a hammer-shaped headand a silicone body embedded with metalcoils. The coils contract, musclelike, whenpulsed with current, and within 200
Robot cartwheels like a caterpillar
GoQBot curls itself up into a ball, then takes off spinning
milliseconds the crawling bot becomes awheel and rolls off at impressive speeds.
“Once you get into a ball and rolling,
you get dramatic increases in speed,”
says Satyandra Gupta, director of the
Maryland Robotics Center at the Uni-
versity of Maryland in College Park.
“This is an exciting development.”
Robots like GoQBot may someday aid
in search and rescue operations that
require both crawling through tight,
dangerous spaces and moving across flat
ground, says Huai-Ti Lin, who created
GoQBot as a graduate student at Tufts
University in Medford, Mass.
Described in the June Bioinspirationand Biomimetics, GoQBot was designedto help researchers better understand the“ballistic rolling” that certain caterpillarsdisplay when frightened.
“You poke the animal and you don’tknow where it’s gone,” says Lin, now atHarvard University. “It’s wicked fast.”
GoQBot can curl itself into a wheel and roll
along at high speed (right to left) like some
caterpillars do to escape predators.
Having a lot of eyespots isn’t neces-
sarily important to a peacock’s mating
success, but having too few virtually