Scientists researching the sexual behavior o primates have made some remarkable discoveries about their sperm counts. The 200 or so species of primates include tiny lemurs, huge gorillas, baboons and humans, and they have a variety of mating habits.
Gorillas, for example live in small groups, in which one dominant male controls several females. Macaques, the most widespread an versatile of monkeys, live in large groups in which competition for females is fierce.
The size of a primate’s testicles is a reliable guide to sperm production. Remarkably, the gorilla has small testicles and produces about sixty five million sperm with each ejaculation. Some macaques, by comparison, have extremely large testicles and ejaculate several thousand million sperm
Scientists say that this difference is a measure of the competition that males face in trying to reproduce. The gorilla, with his harem of females, has no immediate rivals. Male macaque monkeys have many. But even in what seem to be stable relationships, research shows that females are fickle. In all species, insects included, females are rarely faithful. To ensure that their eggs are fertilized, they try to mate with as many males as they can frequently outside their group.
This in turn affects male behavior. Studies show that sperm counts may suddenly change if a male feels threatened. Rats with steady partners ejaculated an average 29.7 million sperm; given the uncertainty of different partners, their sperm counts almost doubled.
Fidelity may possibly affect sperm production in humans. Researchers have found that, if couples spend more time together, the male’s sperm count, which is normally 200 and 500 million, declines. Separated from his partner the male’s sperm count increases, even though the interval between each ejaculation remains constant.
Gorillas, for example live in small groups, in which one dominant male controls several females. Macaques, the most widespread an versatile of monkeys, live in large groups in which competition for females is fierce.
The size of a primate’s testicles is a reliable guide to sperm production. Remarkably, the gorilla has small testicles and produces about sixty five million sperm with each ejaculation. Some macaques, by comparison, have extremely large testicles and ejaculate several thousand million sperm
Scientists say that this difference is a measure of the competition that males face in trying to reproduce. The gorilla, with his harem of females, has no immediate rivals. Male macaque monkeys have many. But even in what seem to be stable relationships, research shows that females are fickle. In all species, insects included, females are rarely faithful. To ensure that their eggs are fertilized, they try to mate with as many males as they can frequently outside their group.
This in turn affects male behavior. Studies show that sperm counts may suddenly change if a male feels threatened. Rats with steady partners ejaculated an average 29.7 million sperm; given the uncertainty of different partners, their sperm counts almost doubled.
Fidelity may possibly affect sperm production in humans. Researchers have found that, if couples spend more time together, the male’s sperm count, which is normally 200 and 500 million, declines. Separated from his partner the male’s sperm count increases, even though the interval between each ejaculation remains constant.
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