Why are there a lot of insects at night? When do sharks sleep? Find out about what some animals do at night in this BBC Earth reader. The Ladybird Do You Know? graded readers series comprises a range of non-fiction STEM titles for young learners of English. Covering a variety of topics, Do You Know? adopts an enquiry-based approach, and includes motivating video content, project work and critical thinking activities to develop students' linguistic and twenty-first century skills.