This Peruvian example, an adult Phrynonax polylepis, has assumed a defensive posture.
Phrynonax polylepis? What in the world is that?

Actually it is a snake that you might know well. Think the Peruvian and Brazilian lineage of Pseustes poecilonotus, the common bird snake, aka the common puffing snake. As mentioned in an earlier blog this month, there has been a “shake up”—a reclassification of the genus once called Pseustes. The big yellow-bellied bird snake, once Pseustes sulphureus, is now Spilotes sulphureus. With this change the remaining 2 (now elevated to 3) taxa are in the genus Phrynonax. P. poecilonotus, once ranging from Central America to South America, has now been restricted to Central America. P. shropshirei, a yellow flecked black species, ranges from Panama to Colombia, Ecuador, and Venezuela and the species P. polylepis has been resurrected for the southernmost of the 2 South American forms. Based on current knowledge it is likely that at least 2 additional species will be erected.