Online resources for learning general animal facts include National Geographic, DK and Encyclopedia of Life. Libraries also have resources in their nonfiction sections.
The National Geographic website has a section dedicated to animals, divided by class and species. Each species listed has an overview plus fast facts such as size and diet. DK has a similar website, organized by sections such as bats, dogs and habitats and ecosystems. Encyclopedia of Life has profiles of many species which list detailed characteristics, including scientific names, population trends and eating habits. The Dewey Decimal class for animal topics in a library is 590.