Functional responses of native and non-native crayfish feeding on snails under predator treatment and control A native signal crayfish B non-native red swamp crayfish C non-native rusty crayfish and D non-native virile crayfish. Lines represent model fit (solid line: predator treatment, dashed line: control). Points represent mean consumption and error bars represent ± SE per density (filled circles: predator treatment, open circles: control; n = 7 per initial density × treatment combination).