Document: GIL-3-56-2

Direct and indirect effects of the predatory dragonfly nymph Anax imperator on green toad Bufo viridis tadpoles.

STAV, G.* ¹, B.P.KOTLER ¹ and L.BLAUSTEIN ²

Ben-Gurion University of the Negev, Sede-Boqer Campus, 84990, Israel ¹
University of Haifa, Haifa 31905, Israel ²

Abstract:
We conducted an artificial pool experiment to assess effects of the predatory dragonfly nymph Anax imperator on green toad Bufo viridis tadpoles. We ran three treatments (with six replicate pools each): (1) free Anax (direct effects on mortality); (2) caged Anax (indirect effects on behavior, development and individual growth rates); and (3) control (no Anax). We added 15 liters (10 cm depth) of water to each pool. After five days, we added 30 three-day old tadpoles, all hatched from the same egg string. Caged Anax were fed with tadpoles three times a week. The experiment ran from 11 April through 4 August. Free Anax eliminated 90% of the tadpoles within three days and all of them within six days. Caged Anax had no effect on the spatial distribution of tadpoles. However, caged Anax caused tadpoles to metamorphose earlier to a larger size (both statistically significant), and to obtain lighter color. This study shows that Anax has a very strong direct effect on the population of Bufo tadpoles. Future experiments will be designed to determine whether the prey responses to the predator are reactions to predation or the result of extra organic matter in this treatment (consequence of Anax feeding and secretion).

Keywords: anax

This abstract is being presented at: 9:00 AM in session:
Oral Session #38: Amphibian Ecology.