Zoogeography is the branch of the natural sciences that studies where, why, and how animals ended up in different parts of the world. It answers questions like "Why are koalas only native to Australia?" and "Where are geckos found?"
While the name suggests that it's a subfield of geography, zoogeography is actually a branch of biogeography, which falls under the umbrella of biology. Zoogeographers study animal distribution: where specific species are found today and where they lived in the past. By examining evolutionary shifts and geological changes — like the movement of continents — they can determine the processes that led animals to their current habitats.