When I first spotted this snake I assumed it was yet another in the long line of default snakes that we had been seeing. (To be fair, they are similar in color and pattern, and we did see three more that same night.) Closer inspection revealed a different head shape and somewhat different pattern, and a little research shows that this is one of the Lycodryas species (called "Stenophis" in The Authority, but subsequently changed).

Madagascar herp expert Dr. Mark Scherz saw photos of this individual and said that it was either Lycodryas granuliceps or Lycodryas guentheri, and that the only way to be sure would be to count the ventral (belly) scales, which we did not. Lycodryas granuliceps is only currently known from the extreme north and northeast of Madagascar, so this seems more likely to be Lycodryas guentheri, which is known from the south. But I can't be confident.

Here is a list of all the reptiles and frogs I saw on this 2023 trip to Madagascar.