Dichotomous (branching) keys are often used to identify species. At each point, the user chooses between two choices to get to the next point, eventually eliminating all other choices and identifying the species.
The keys below are adapted from those in the Field Guide to Amphibians and Reptiles of Illinois and the Field Manual of Illinois Mammals. To purchase copies of these (and other) field guides, visit our online store.
Key to Frogs and Toads of Illinois
Key to Salamanders of Illinois
Key to Skulls of Illinois Mammals