Reviewing What We've Learned

Day 180: All right, class, let's review what we've learned about frog species this week. And before you accuse me of using the editorial "we," let me remind you that I've been learning right alongside you, and now I feel more confident in my ability to differentiate Cascades Frogs from Northern Red-legged Frogs.

First of all, the most reliable field characteristic seems to be the spots on the back. Cascades Frogs have well-defined spots as opposed to those of Red-legged Frogs which have a blurred or somewhat indistinct outline. Cascades Frogs have yellow bellies and legs, but the observer can be misled by a young Red-legged Frog whose red pigmentation has not yet developed. Often, the red pigmentation isn't visible on the legs, but may be seen in a ventral view. Of course that means dip-netting your specimen and subjecting it to the indignity (however brief) of being turned over on its back. Unless you are engaged in a formal scientific study, I strongly advise against this. The next characteristic is a little more vague. Red-legged Frogs only extend in range to approximately 2800-3000 feet elevation, overlapping the range of Cascades Frogs in a wide band. With climate changes occurring, this range may move up, creating a broader area in which the two species may coexist.

The Cascades Frog shown in this photo was found at 3000' elevation, very near an area where Red-legged Frogs have also been sighted. However, I am happy to report that my initial assessment of its identification has been confirmed by two experts in the field of "frogology." Incidentally, Cascades Frogs were recognized as a separate species in 1939. The holotype specimens were collected in Mount Rainier National Park.