Avoiding being stung or bitten – prey capture behaviors of the ant-eating Texas horned lizard (Phrynosoma cornutum)

ABSTRACT Horned lizards (Phrynosoma) are specialized predators, including many species that primarily feed on seed harvester ants (Pogonomyrmex). Harvester ants have strong mandibles to husk seeds or defensively bite, and a venomous sting. Texas horned lizards possess a blood plasma factor that neutralizes harvester ant venom and produce copious mucus in the pharynx and esophagus, thus embedding and incapacitating swallowed ants. We used high-speed video recordings to investigate complexities of their lingual prey capture and handling behavior. Lizards primarily strike ants at their mesosoma (thorax plus propodeum of abdomen). They avoid the head and gaster, even if closer to the lizard, and if prey directional movement is reversed. Orientation of captured ants during retraction is with head first (rostral), thus providing initial mucus coating of the mandibles. Prey capture accuracy and precise handling illustrates the specificity of adaptations of horned lizards in avoiding harm, and the challenges lizards face when feeding on dangerous prey.

Novel cooperative antipredator tactics of an ant specialized against a snake

Eusocial insects can express surprisingly complex cooperative defence of the colony. Brood and reproductive castes typically remain in the nest and are protected by workers' various antipredator tactics against intruders. In Madagascar, a myrmicine ant, Aphaenogaster swammerdami , occurs sympatrically with a large blindsnake, Madatyphlops decorsei . As blindsnakes generally specialize on feeding on termites and ants brood by intruding into the nest, these snakes are presumably a serious predator on the ant. Conversely, a lamprophiid snake, Madagascarophis colubrinus , is considered to occur often in active A . swammerdami nests without being attacked. By presenting M . colubrinus , M . decorsei and a control snake, Thamnosophis lateralis , at the entrance of the nest, we observed two highly specialized interactions between ants and snakes: the acceptance of M . colubrinus into the nest and the cooperative evacuation of the brood from the nest for protection against the ant-eating M . decorsei . Given that M . colubrinus is one of the few known predators of blindsnakes in this area, A . swammerdami may protect their colonies against this blindsnake by two antipredator tactics, symbiosis with M . colubrinus and evacuation in response to intrusion by blindsnakes. These findings demonstrate that specialized predators can drive evolution of complex cooperative defence in eusocial species.