Can we really know what animals are feeling? New research shows that bull sharks have complex social relationships. But some think animal emotion will always remain a mystery.
Sharks have frenemies, say scientists
Fin-tastic friends: Research into the social lives of bull sharks suggests they form complex bonds and choose their companions, challenging the long-held image of these marine predators as lonely, mindless hunters. Glossary
Predators - Animals that prey on and eat other animals.
Fiji - A country made up of more than 300 islands located in the South Pacific Ocean, famous for its coral reefs and clear lagoons.
Bull Sharks - A type of large, powerful shark known for being able to live in both saltwater and freshwater. They are often found in shallow coastal waters.
Standoffish - A word used to describe someone (or an animal) who is unfriendly, cold, or keeps their distance from others.
Intelligence - How clever someone is.
Rainbow trout - The rainbow trout is native to cold-water rivers which run into the Pacific Ocean in Asia and North America.
Venom - A poisonous substance secret by such animals as snakes, spiders and scorpians.
Subjective - Influenced by personal tastes.
Empathy - The capacity to understand and feel the suffering of others.
AI - A computer programme that has been designed to think.
Philosopher - A thinker who comes up with ideas about big questions in life.