ELI5: Explain Like I'm 5

Distance sampling

Distance sampling is a way that scientists can measure the size of an animal population without counting every individual animal. Instead of counting, the scientists look at how far away the animals are from them. They measure the distance to the first animal they spot and then count how many more animals they see in closer distances. They do this several times in different parts of the area to get a better idea of how many animals are living there.