Abstract: The green toads, Bufo viridis breed in temporary desert ponds of variable duration and exhibit extreme plasticity in the timing of metamorphosis. Pond duration depended on initial depth and frequency of rainfall. Tadpoles in shorter duration ponds metamorphosed earlier than tadpoles in longer duration ponds. The larvae complete their development rapidly before the pond dried, but resulted in small size at metamorphosis. The effects of changing resource availability on the timing of metamorphosis were examined by raising the larvae in a factorial field experiment manipulating food level, larval density and pond duration. At constant pond duration, tadpoles at constant high food level metamorphosed earlier at largest sizes. At low food level, tadpoles metamorphosed at a uniformly small size, but varied between treatments in the time required to reach that size. Tadpoles from both decreasing density and low food treatments metamorphosed earlier than tadpoles from increasing density and low fond treatments. These results support the idea that tadpoles can respond adaptively to resource variation.