INTERACTIVE EFFECTS OF PREDATORS AND EARLY LARVAL DYNAMICS OF THE TREEFROG HYLA-CHRYSOSCELIS

Manipulated the presence and absence of 2 predators (salamander Notophthalmus viridescens, crayfish Cambarus bartonii) and their tadpole prey (Hyla chrysoscelis) in a series of artificial ponds. Early samples predicted that the predators would interact to determine tadpole survival and size. The predators did not act additively to determine tadpole abundance: more survived in the presence of both predators than was predicted, a higher order interaction most likely caused by physical interference between the predators and predator avoidance by the tadpoles. Early samples correctly predicted higher order interactions would be seen on tadpole growth, but failed to predict their direction because the biological interactions changed over time. Early in their larval period, tadpoles behaviourally avoided predators, which caused slower growth, but later tadpoles in predator treatments grew faster due to diminished intraspecific competition. -from Author