Animals do the strangest things. Why do dogs eat grass and cats bring their owners dead birds? Zoologists look to animals' behaviour to understand them. Can they think, laugh, love, grieve? Do they use tools? Are they solitary or do they live in communities with complex hierarchies? The most practical application of studying animal behaviour is simple: knowing how a certain animal normally behaves is indispensable when creating a happy and comfortable home for a pet or zoo animal.