Why do howler monkeys have white balls

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See Subscription Options. Full Transcript. More Podcasts. Download MP3. See all podcasts. Support science journalism. Knowledge awaits. See Subscription Options Already a subscriber? Alternatively, big voiced-males might be able to fend off other males, reducing competition for their sperm, and so not need large testes. Studies have also found inverse relationships between testicle size and traits that help males beat competitors in physical combat.

In one, dung beetles with the biggest horns were found to have the smallest testicles. The new study is the first to find a link between sperm production and vocal ability, and suggests that howls might have a similar role to the horns in fending off rivals and winning access to mates.

The researchers also tested a competing hypothesis: that more powerful roars had evolved in species that lived in denser forests, so they could be heard more easily. They also studied recordings of howls and compared them with other animal noises. Tico Times. Sign in. Forgot your password? Get help. Create an account. Password recovery. No menu items! Thursday, November 11, Local News.