Comparative vulnerability of Indosylvirana temporalis and Clinotarsus curtipes (Anura: Ranidae) tadpoles to water scorpions: importance of refugia and swimming speed in predator avoidance

Abstract

The comparative vulnerability of two co-existing tadpole species (Indosylvirana temporalis and Clinotarsus curtipes) to their common predator, water scorpions (Laccotrephes sp.; Hemiptera: Nepidae), and the importance of refugia in predator avoidance were studied in the laboratory. In a total of 60 experimental trials, 10 tadpoles each of I. temporalis and C. curtipes of comparable body sizes were exposed to water scorpions (starved for 48 h). Thirty trials included refugia while 30 did not. The results of this study showed that in both the absence and the presence of refugia C. curtipes tadpoles fell prey to water scorpions more frequently than I. temporalis tadpoles. A main difference between the two species is the speed of swimming; V_max of C. curtipes (24.73 cm/s) tadpoles is lower than that of I. temporalis (30.78 cm/s) tadpoles. This is likely to be the reason why more C. curtipes tadpoles were preyed upon than were I. temporalis tadpoles. Predation risk of tadpoles of both species was affected significantly by the presence of refuge sites. The vulnerability of both tadpole species was lower where refuge sites were available. The present study clearly shows that I. temporalis tadpoles avoid predation by water scorpions more effectively than do C. curtipes tadpoles.