Terrestrial snails use predator-diet to assess danger

Some aquatic snails are able to use chemical cues (kairomones) to differentiate between predators that have fed on snails and predators that have eaten other prey. However, it is unknown if terrestrial snails are able to differentiate between snail-fed predators and predators that have not recently consumed snails. Here we document diet-based chemical discrimination of a predator, the ground beetle Carabus carabus, by a terrestrial snail Theba pisana. When exposed to the feces of snail-fed beetles, snails initially stopped all movements and then increased climbing speed. The snails also decreased the time to deposition of their egg clutch. The snails did not react to an extract of crushed snails. Snails had only a partial reaction to the feces of beetles that had fed on chicken (Gallus domesticus) livers - they decreased climbing speed but did not alter egg laying times. These responses may be adaptive in that they allow snails to differentiate between individual beetles that may pose an immediate threat and beetles that may not. This is one of only a few studies to examine predator-diet effects on reproductive behavior.