Two Neotropical Snakes Attacked as Prey by Army Ants in Costa Rica

Geophis hoffmanni and Ninia sebae belong to a group of snake species informally referred to as "goo-eaters" due to their diet consisting entirely of soft-bodied invertebrates. Geophis hoffmanni is a nocturnal, terrestrial, and fossorial snake often found in herbaceous vegetation and leaf litter near humid areas. Ninia sebae is both terrestrial and fossorial, and is commonly found under logs, boards, leaf piles, and various types of cover objects. One of the most formidable predators in many tropical forests are army ants, which forage in "raids" involving large numbers of ants searching for food simultaneously in confined areas. The most prevalent species is Eciton burchelli, widely distributed across the Neotropics. In Costa Rica, Labidus spininodis is also common, primarily inhabiting wet forest areas. On January 2, 2022, we observed a colony of Eciton burchellii attacking a Geophis hoffmanni individual at Selva Verde Lodge. The ants killed the snake, but we couldn't observe what happened afterward. On September 23, 2022, we encountered a swarm of Labidus spininodis ants attacking a Ninia sebae individual at Soltis Center. We couldn't determine whether the ants killed the snake, but it remained motionless after approximately 40 minutes of ant attacks, and some ant workers were seen cutting pieces from the snake's body. Both incidents occurred in the northern lowlands of the Caribbean slope of Costa Rica. These are two unprecedented cases of predation on Neotropical dipsadid snakes by two species of army ants. These instances mark the first reported cases of these emblematic terrestrial predators capturing relatively large vertebrates.