A calico snake (Oxyrhopus petolarius) cruises in the leaf litter in search of prey, glinting from my head torch like an obsidian gemstone. This species belongs to the Dipsadinae (sometimes elevated to family status), a diverse subfamily encompassing other more popular colubroids such as Imantodes, Leptodeira, and Sibon. Calico snakes occur throughout Central America to southeastern Brazil and Bolivia. They are opportunistic predators, eating a variety of prey including lizards, snakes, amphibians, birds, small mammals. Oxyrhopus petolarius is variable in color throughout its range. This individual from the Osa peninsula was jet black with over a dozen faint red stripes across the body. Others can have much more striking patterns, with red-orange, yellow, and white bands, or even be completely unpatterned. The beautiful mottled red band on the head has led to another common name, the forest flame snake.
Oxyrhopus is one of a plethora of colubrids that are thought to mimic venomous coral snakes. Within the dipsadines there is remarkable diversity in color pattern with a continuum of resemblance to coral snakes: some species are “good” mimics while others have much less convincing mimetic patterns. Many of these snakes will also employ similar antipredator behaviors to coral snakes, spiraling and raising their colorful tail tips and twitching in an elastic and sporadic manner. Historically this system has been considered as Batesian mimicry, under the assumption that mimics present predators with a dishonest signal of unpalatability / toxicity. However, ongoing research has revealed the presence of harmful toxins throughout rear-fanged colubrids, making it challenging to assess the dynamics of mimicry. Really awesome work is currently going on in Alison Davis Rabosky’s lab at the University of Michigan exploring the relationship between color, behavior, toxicity, and mimicry.