Predation on amphibian eggs and tadpoles by common predators in acidified lakes

Eggs and three different stages of premetamorphic tadpoles of moor frog Rana arvalis and common toad Bufo bufo were offered to the following potential predators in acidified lakes: newt Triturus vulgaris , water beetles Rhantus exoletus and Dytiscus lapponicus , dragonfly larvae Leucorrhinia dubia and Aeshna spp., water boatman Notonecta glauca and water bugs, Cymatia bonsdorffi, Glaenocorisa p. propinqua , and Corixa dentipes. The predation pressure on eggs of R. arvalis was low due to thick jelly. The eggs of B. bufo were not attractive to predators with chewing mouth parts due to unpalatability but predators with sucking mouth parts were not repulsed. Tadpoles of R. arvalis were eaten by all predators but tadpoles of B. bufo were unpalatable to most predators. The predators used in the experiments are the new top predators in acidified fishless lakes. They may contribute to the reduction of populations of R. arvalis in acidified areas.