As an adult, the mock viper attains a length of only 15 inches.
Hirnan, our boat captain, was not a great fan of snakes. Frogs, salamanders, turtles, crocodilians, lizards were all OK, but when snakes were encountered, they and Capitan Hirnan quickly parted company.

We had been were on a discus (tropical fish) finding foray along waterways on the Peruvian side of the Rio Putumayo, a river that serves as a border between Peru and Colombia. The search took us up and back along many creeks, and I usually found time for at least a cursory search for herps.

At most stops we found anoles, geckos, and at least a few fer-de-lance. The presence of the latter kept us all on our toes, but none of us moreso than Hirnan. But there was this one memorable stop—the one where there seemed to be a fer-de-lance near every tree and a few just coiled quietly in the rather tall grass. So Hirnan did what every human who is adverse to snakes would do. He reached down and picked up a fair-sized limb, about 8 feet long, to brush the pit vipers out of the way. Happily Hirnan lifted the improvised snake stick, brought it upwards to a vertical position, let out a scream, and headed, on the run, back to the boat? Apparently a small snake, a mock viper, Thamnodynastes pallidus, had n crawling over the limb, held to and been lifted to a position over Hirnan,s head, lost its grip and fallen on his shoulder.

What’s that saying about the best laid plans of mice and men?