Snails and slugs occupy the frontier of animal welfare consideration — their capacity to suffer is uncertain but the precautionary case for care is growing.
Snails and slugs sit at the edge of welfare consideration where scientific uncertainty is greatest. Evidence of nociception and protective responses suggests the capacity for something like suffering cannot be ruled out. The practical welfare implication is clear: where effective alternatives exist, methods causing prolonged distress should be replaced. Metaldehyde poisoning — a slow, painful dehydration death — can be entirely replaced by ferric phosphate pellets or physical barriers with no welfare cost to the gardener and significant welfare benefit to molluscs.