Dunn’s team analyzed the biological “budget” of these primates and found a direct negative correlation: males with large ...

A black howler monkey vocal chorus is seen at the Biological Field Station Corrientes, Argentina in this handout image released to Reuters on October 21, 2015. REUTERS/Mariana Rano/Handout via Reuters ...

Granddaughter Kyndra had a blast celebrating her 7th birthday at the Denver Zoo. The hour was getting late. We were exhausted. The roar of the sad lion and laugh of the hyena faded into the distance ...

Baby, I'm howlin' for you. Male howler monkeys make deep and boisterous calls to attract mates, but the deepest-pitched songs may come at cost: the size of their testicles. A new study in the journal ...

Reader John Honeyman shared this amazing photo of a howler monkey spotted in Santa Teresa, a beautiful town on Costa Rica’s Nicoya Peninsula. Santa Teresa is known for its stunning beaches, but it’s ...

WASHINGTON, Oct 22 (Reuters) - The howler monkeys whose guttural calls reverberate through Central and South American rainforests possess a secret that the males of the species may prefer to be left ...