Hurter's Spadefoot Toad (Scaphiopus hurterii) is closely related to the Eastern Spadefoot Toad (Scaphiopus holbrooki) and occupies the eastern half of Texas. It is usually greenish or brownish with vague striped pattern on its back.
The widespread Spadefoot of the southwestern US is the Couch's Spadefoot (Scaphiopus couchii). In Texas, it is found in the western 2/3 of the state. Couch's Spadefoot is highly variable in pattern, but usually shows some pattern of a yellowish or greenish background with an irregular mottled or spotted black pattern on the back. It rarely shows the striping seen in S. hurterii.
Not only is there a superficial resemblance in size and coloration, but these two species have similar calls. Their calls are often described as "dyspeptic groans" and can sound similar from a distance.
Here is the call of Scaphiopus hurterii. This species has a "doppler" effect to its call where its shorter notes descend in pitch. It is somewhat remniscent of impersonating the sound of a car passing at high speed.
And here is the call of Scaphiopus couchii. This species has a call that goes up then down in pitch and is usually longer in duration than the call of the Hurter's Spadefoot.
They don't sound that similar up close, but from a distance they can be suggestive of each other. But while they are similar sounding, the "shape" of the call notes and their length is different. Here is a few seconds of S. hurterii followed by a few seconds of S. couchii.
The darkest line on the spectrograph represents the carrier (dominant) frequency of the call. I have drawn in a red line indicating the approximate shape (slope) of the call in an effort to demontrate the differences in their relative shapes.
Here's a comparison of a chorus of S. hurteri from DeWitt County, Texas -
Hurter's Spadefoot Chorus - DeWitt County
and a chorus of S. couchii from Dimmitt County, Texas -
Couch's Spadefoot Chorus - Dimmit County
Once you learn the general differences in length and shape, their calls are not too difficult to tell apart.
© Chris Harrison 2014