jueves, 14 de agosto de 2008

"Cross Dressing" Lemurs Appear Male to Avoid Conflict

Matt Kaplan
for National Geographic News
July 24, 2008
Young female red-fronted lemurs in Madagascar adopt male coloration to dupe their aggressive female groupmates, a new study found.

These "cross dressing" primates thus avoid the wrath of older females, which would attack them to reduce sexual competition.

All red-fronted lemurs are born with the same greyish brown fur and rusty-red crowns that distinguish adult males. 

At 7 to 17 weeks later, females' coats change to a cinnamon hue, and their crowns become white.

"We knew from our longer-term observations that there was a lot of female aggression in red-fronted lemurs," said study author Claudia Fichtel of the University of Göttingen's German Primate Center.

"Females compete fiercely over limited breeding opportunities, and we wanted to know if hiding femininity was a way to avoid being attacked," Fitchtel said.

(See a photo of an endangered ring-tailed lemur.)

Not a Target

German researchers monitored a wild lemur population in the Kirindy forest in western Madagascar for five months and recorded behavioral changes as their coats changed color. 

But the scientists also faced a problem: Since all infants appear male, the theory that young sport different colorations to thwart conflicts is tricky to investigate. 

This led Fichtel and her colleagues to look very closely at older females and monitor their attacks. 

They found that males and all young females disguised as males were not targeted by the hostile older females.

Fichtel and her colleagues argue that appearing male has evolved as a defense to keep females from attacking until the masquerading females are strong enough to handle it. That tends to be between 7 and 17 weeks of age.

(Related: "Rainfall Helps Baby Lemurs Survive, Tooth Study Shows" [November 14, 2005].)

Red-fronted lemurs are not the only primates whose youngsters are colored differently than adults. 

In other species this disparity has often been explained as an adaptation that makes infants more noticeable to groupmates. Adults are then more likely to care for and protect infants, Fichtel added.

The study appears in the July issue of the Journal of Physical Anthropology.

Female Dominance

"This provides a fresh perspective into why some primate offspring have a dramatically different coat color," said Sylvia Atsalis, a primatologist at Lincoln Park Zoo in Chicago.

"It tickles scientific minds to think—through a new perspective—about a condition that occurs in many species," she added.

More in-depth analyses should be made into female lemurs and their behaviors, other scientists said.

"There has been a long-running argument about how aggressive red-fronted lemurs are to each other," said Alison Jolly, a primatologist at the University of Winchester in the United Kingdom.

"Most of their social life is cuddling and grooming, [but] once in a long while females viciously throw other females out of the group, or more rarely, they have been seen to kill and actually eat another animals' infants," she said. 

"The question is, Is infanticide or targeting so rare that it couldn't have much influence over evolutionary time?"

(Read: "Ecotourism Driving Tibetan Monkeys to Infanticide" [July 20, 2007].)

Patricia Wright, a primatologist at Stony Brook University in New York, added that genetic tests should be done to see how lemurs perceive color.

"We've only recently learned that not all lemurs see color," Wright said.

"Sometimes only females have color vision, a trait that makes males dependent upon them for finding berries and secures female dominance."

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