ESTIMATING PREY SIZE AND NUMBER IN CRAYFISH-EATING SNAKES, GENUS REGINA

Abstract

Snakes of the genus Regina feed almost exclusively on crayfish. The paired, sym- metrical gastroliths of crayfish are not digested and are detectable from x-rays of the snake. Gastrolith length is directly proportional to carapace length and can be obtained from x-rays. Carapace length can be converted to kcal of ingested energy. Using these relationships and repeated captures of radio-telemetered Regina, estimates of food consumption and energy intake by free- living snakes are feasible. New information on prey selectivity, feeding behavior, and predator- prey size relations in Regina grahami and R. septemvittata are presented and compared with similar data for other snakes.