Posted 25 April 2008 - 07:07 PM
Distinguishing American from Fowler's toads:
There are several characters, and none of them are perfectly diagnostic. If you try all of them you can usually successfully ID your toad. Unless it's a hybrid. Toads are the oaks of the amphibian world.
First- as Matt mentioned, there are differences in the number of warts in each dark dorsal spot, which is due to Fowler's having both larger spots and smaller warts than Americans. Fowler's toads typically have 3 or more (sometimes up to 10) warts in each large dark dorsal spot; Americans normally have 1-2 warts per spot. However, both species may have linear dorsal spots containing 3 or more warts. Additionally, the dark spots of Fowler's toads are almost always encircled with cream or brassy border, while American's are usually not.
Second- the junction between the transverse posterior portion of the cranial crest (the postorbital ridge) and the parotoid gland is distinctly different in the two species. Fowler's have the parotoid broadly adjoining the postorbital ridge. Americans have the two separated or touching in only a small contact area; they may also often have a terminal spur extending longitudinally from the distal end of the postorbital ridge to the parotoid.
Third- Americans often, but not always, have enlarged, often fused, spinous warts on the shank. Fowler's never have these.
Fourth- Americans tend to have two distinct size classes of warts; Fowler's warts are generally more uniform or at least smoothly grading in size.
Fifth- the color ranges of the two species overlap considerably, but Americans are often brick red (especially in the lower Ohio Valley and westward) or blackish, and Fowler's are sometimes yellowish or greenish; the opposite is seldom true. Americans often have the dark dorsal spots blending into the dorsal ground color, while Fowler's are almost always boldly spotted. Fowler's almost always have a light vertebral stripe, while Americans may or may not. Americans may have fully spotted or reticulately patterend venters (especially east of about 86 W), while Fowler's seldom have ventral spots except on the chest and throat.
Sixth, and probably most reliable- Americans have a long (often 30 seconds +), high, musical trill. Fowler's have a short (usually under 5 seconds), slightly deeper, much more nasal, explosive trill (often expressed "Waaaahhhh!"). The pulse rates of the two calls are very similar.
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