Scientists have documented same-sex behavior in many animals. Learn what it means, how it varies, and why human labels can mislead.

Few animals depend on timing as tightly as the kākāpō. This flightless parrot is found only on a few predator-free islands ...

Thought of the day: Pablo Picasso’s words challenge readers to reconsider how they perceive themselves and others. Perhaps ...

A NASA image of the snow-dusted Grand Canyon has created a striking optical illusion, making the vast chasm-more than a mile ...

In Burundi, large-scale tea production is hampering efforts to protect endangered species, such as chimpanzees. A tea plantation stretches as far as the eye can see on the edge of Kibira National Park ...

On a remote island in North Macedonia, male Hermann’s tortoises outnumber females 19 to 1, an imbalance driving the ...

Human newborns arrive remarkably underdeveloped. The reason lies in a deep evolutionary trade-off between big brains, bipedalism and the limits of motherhood.

Scientists at Michigan State University have uncovered the molecular “switch” that powers sperm for their final, high-speed dash toward an egg. By tracking how sperm use glucose as fuel, the team ...

As Valentine's Day approaches, we take a look at monogamy and its alternatives among animals — including humans.