The simplest prey-selection model predicts that predators select prey to maximize energetic benefit and minimize handling time. We tested whether or not energetic indices predict stomatopod preference for prey. The energetic indices included: 1) the ratio of energetic return (mass of prey tissue, M) per unit handling time (feeding duration, T); 2) the ratio of energetic benefit (caloric value of prey tissue, E) to energetic cost (caloric value of energy expended, C); and 3) the ratio of net energetic benefit (caloric value of food minus the caloric value of energy expended, NE) to handling time.

Stomatopods, characterized by highly specialized raptorial feeding appendages, strike and smash the shells of prey such as snails. The prey-capture strike is one of the fastest known animal movements. Stomatopods, presented with snail shells of three size classes (5–6, 8–9, 11–12 mm in length), preferred intermediate and small snails. Oxygen consumption increased an average 2.5-fold above resting rates during feeding and increased linearly with strike frequency. The energetic cost per strike was 1.6 ± 0.2 μl O2. Stomatopods obtained more snail tissue from smashing larger snail shells. However, longer handling times were required to open shells of greater size. To obtain snail tissue, stomatopods struck larger shells a greater number of times. Strike frequency (0.72 strikes/min) was independent of shell size. The amount of snail tissue obtained per strike (0.044 mg/strike), M/T, NE/T, and E/C were all independent of snail size. The mean energetic benefit per strike (0.23 calories/strike) was 13-fold greater than the energetic cost per strike (0.017 calories/strike). Energetic cost, energetic benefit and handling time appear not to be the sole variables that explain stomatopod prey selection.