Are there Fer-de-Lance on the Nicoya Peninsula ?

 Arguably Central America’s most deadly and widespread venomous snake is the Fer-de-Lance or Terciopelo. It can be found in a wide variety of habitats throughout Costa Rica.  Studies have even shown that it can survive -- and indeed thrive -- in disturbed habitats in close proximity to humans.

Fer-de-Lance (Bothrops apser)

The big "question mark" remains on the Nicoya Peninsula.  Although no confirmed records exist for the region, the thing I've learned over the years is that doesn't stop most people from believing they are here.

I actually still hold out hope that they do occur here; there is certainly suitable habitat at the southernmost tip in Cabo Blanco national park, but so far I have never seen one. I do however have an alternate theory of what people are seeing.  

Lyre Snake (Trimorphodon biscutatus)

 Fer-de-Lance (Bothrops apser)

The Lyre Snake (Trimorphodon biscutatus) is a common enough snake throughout the Peninsula in multiple habitats, and could very well be the infamous Nicoya Fer-de-Lances people are seeing. Here are a few reasons why: they have a very similar pattern - it’s not a distinct "X" pattern like the Bothrops, but it does overall have very similar coloration. Their behavior when first encountered is strikingly similar: in Panama I came upon a Fer-de-Lance moving along a bank side.  When it spotted me it quickly coiled up start rattling its tail on the leaf litter and brought its head up. I have witnessed the Lyre Snake do the exact same thing.  Now unlike the Fer-de-Lance it won’t make as tight of a coil or stay like that for long: they usually try the threatening position then scatter. The tail rattling though is the exact same in both, and for me it’s one of the more compelling similarities. If you only get a quick look the lyre snake will also flatten its head in a similar fashion to a pit viper. Their eyes can also fool you at first glance they can create a very narrow slitted iris similar to a pit viper.

The flat triangle shaped head distinct in Pit vippers.

If you were to take a close enough look though you would notice the lack of sensory pit glands that all pit vipers posses.

Sensory pit glands on the front of a Fer-de-Lance

So for now I’m still very skeptical that Fer-de-Lance occur widespread throughout the Peninsula, but I still very much hold out hope they are here and that I can finally confirm their occurrence here.