Can we know what animals are feeling? Scientists are looking at ingenious ways of exploring other creatures’ emotions, with far-reaching implications for how we treat them.
The quest to know what makes a tortoise happy
Sedate: The Sonoran desert tortoise (above) plods its range, browsing wildflowers, scrub grasses and cactus. Glossary
Bison - A wild ox, with a humpback and shaggy hair, native to North America and Europe.
AI - A computer programme that has been designed to think.
Predators - Animals that prey on and eat other animals.
Hormones - Chemicals created inside living creatures. They are used to send messages from one part of the body to another.
Adrenaline - A hormone made by the body in response to a stressful or threatening situation.