Dichotomous keys are very commonly used in biology – you may have seen one before. Dichotomous means two-branched, and these keys are a useful way to break down an identification process into a number of simple steps. There are paired descriptions of different traits, each numbered. For each pair (beginning at no. 1), click the option (a) or (b) that best fits your animal, and go to the numbered characteristic given by that option. Choose the best option again, and so on until you come to a species. Click on the name to see the species description, and see whether the description fits what you saw. If it doesn’t, try the key again, especially if you were not sure of one or more of your choices.
For example, suppose I have seen a small frog in the Lower Mainland. I look at its eyes and see that it has horizontal pupils, so I click on 1(b). This directs me to no. 3; I choose (b) again because my frog has smooth skin. In no. 4 I choose (a) because my frog has a dark eye stripe and sticky pads on its toes. I discover that I have seen a Pacific Chorus Frog (and a cute little creature it was, too).