beelzebufo: (Default)
Beelzebufo ([personal profile] beelzebufo) wrote2010-06-10 02:05 pm

americanus vs fowleri

The american and fowler’s toads at my field sites frustrated me for a while. You’ve got one, you’ve got the other, and then you have HYBRIDS. When you’re a newcomer to herps and just learning how to ID, the hybrids become the bane of your existence.

You think you’ve got it down (click on the photo link to see the anatomy specified):

American toad, Bufo americanus*
  • Dorsal side: mottled

  • Ventral side: < 2 warts per black splotch

  • Ventral side: neither parotiod* touches the post orbital ridge, but might touch the ridge spurs

Fowler’s toad, Bufo fowleri
  • Dorsal side: white with one dark spot at chest

  • Ventral side: > 3 warts per black spot

  • Ventral side: both parotoid glands touch the post orbital ridge:

Then you find a hybrid and become confused all over! You wonder why you're going through these futile efforts because the only conclusion you come to is that toad pee is fairly inoffensive. Although the two species easily hybridize, they (should theoretically) be temporally separated. Americans breed far earlier in the year than fowleri. Furthermore their breeding calls are quite different, but apparently the girls don’t heed the advertisements.

This one is one of the most common types we find:

Fowler seeming dorsal:

American seeming ventral:

The placement of the parotoid also varies, but I can't find any good shots of that. These hybrids really are all over the sites. I used to agonize over the ID (thinking the confusion was due to ignorance). Angus thought we were just making mistakes instead of finding so many hybrids. But then he came on some surveys and found ones that confounded him too. So now I look and if it’s indeterminate I just write Bufo and MOVE ON.

*In a quick google search I’ve found these glands spelled paratoid, parotoid, and parotid in journal articles. WTF I give up.
**I know taxonomy is switching to Anaxyrus from Bufo for these two, but apparently I am resistant to change.