Because there is no apparent way to climb the leadership ladder, says UCLA primatologist Joan Silk, "it could be pretty depressing from a human perspective if your mother is a low-ranking female." Oldest daughters of dominant females, however, don't necessarily inherit the top spot. Often the youngest daughter receives that privilege. "Mothers often form coalitions with their youngest daughters," explains researcher Sidney Perloe of Haverford College in Pennsylvania. Such coalitions, he says, maintain peace by reassuring the matriarch that an older daughter will not overthrow her.

But in the regularly-fed park populations, Perloe says, "Life is a little too easy, so the males sometimes don't leave." This can lead to social tensions and increase the odds of genetically harmful inbreeding.

For both male and female snow monkeys, the key to evolutionary victory is having the most offspring, but being at the top doesn't necessarily guarantee success. Linda Fedigan, a scientist at the University of Alberta in Canada, found that low-ranked females can outproduce higher-ranked macaques, perhaps because the latter experience the psychological stress that accompanies leadership. And dominant males are often spurned by their female counterparts because the males have lived with the troop too long, although they can still influence mating patterns by chasing off lower-ranked competitors.

Photos: Masashi Koizumi.