Smaller than in multi male species but larger than in

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smaller than in multi-male species, but larger than in single-male species - why aren’t they as small as in single-male species? - what might this suggest about the effectiveness of these two strategies for monopolizing access to the females? - this is something you might look for at the zoo, especially if you bring binoculars. Compare the size of testes of: - male baboons or male chimps, who live in multi-male, multi-female groups - to male gorillas (at the SF zoo), who live in single-male groups (or groups in which subordinate males do not mate with the females) - or male gibbons or siamangs (at the Oakland zoo), who live in monogamous pairs - try explaining this to the people standing near you and see what happens! - intersexual selection (mostly female choice) in primates - since receptive females are scarce and males are plentiful, females can be picky about which males they mate with
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Intro to Biological Anthro F 2011 / Owen: Sexual selection p. 5 - they don't have to mate with any particular male, since there are plenty of others to choose from - in contrast to males, who benefit from mating with any female they can find - but why would pickiness improve a female’s reproductive success? - two general reasons: - 1. some males might have genes that, when inherited by the offspring, would improve its fitness (mature faster, be healthier, etc.) - any female that tended to choose males with better genes would have more surviving offspring, or ones that would reproduce more - these daughters will tend to also get the mothers preference for that kind of male, so the preference will become common - so females will tend to evolve preferences for any visible trait that indicate beneficial genes - for example, in peacocks, large tail feathers might indicate healthier males - so females that tend to mate with males with large tail feathers would produce healthier offspring, and since those better-surviving offspring also tend to have the mother’s preference for long tail feathers, that preference becomes more common - 2. some males might have parenting traits that benefit the female's survival and that of her infant - for example, some males might be more prone to vigorously defend her and her offspring from predators or infanticidal males, or to defend a larger territory so that she has more food to eat - any tendency of females to select males with these parenting traits will be favored by sexual selection - because females who tend to mate with these males will leave more surviving offspring than those that do not - Whatever the reason, if females prefer some trait in mates, those traits will get into more offspring, and will become more common - how can we tell if female choice was important? - if a visible trait is found only among males and it does not seem to be related to male-male competition - example: fleshy noses of proboscis monkeys - female-choice intersexual selection has been shown to be important in many non-primate species - there are some primate species in which it may have played a role, too -
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