POND DRYING, PREDATORS, AND THE DISTRIBUTION OF PSEUDACRIS TADPOLES

Twenty-two natural ponds in southeastern Michigan were monitored to de termine the distribution of two species of tadpoles, the spring peeper (Pseudacris crucifer) and the striped chorus frog (P. triseriata), wi th respect to pond drying and predation. These species breed in ponds ranging from those that dry each summer to those that are permanent on the order of decades. Among nonpermanent ponds, the timing of pond dr ying varies among years; and particularly in dry years, many ponds dry before larvae reach metamorphosis. More permanent ponds have higher d ensities of tadpole predators, and predators are larger in body size. Predator taxonomic composition also changed markedly over the permanen ce gradient. More permanent ponds contained several taxa (e.g., salama nders, fishes) known to have pronounced effects on tadpole survivorshi p. Pseudacris triseriata and P. crucifer larvae co-occurred in most po nds. There was, however, large variation in relative abundance: P. tri seriata larvae were totally absent from permanent ponds and were most abundant relative to P. crucifer in the most temporary ponds. Pseudacr is is triseriata larvae grew faster and reached metamorphosis sooner t han P. crucifer. Relative density measurements over the course of the larval period suggest that P. crucifer survived better than P. triseri ata prior to metamorphosis or pond drying. Larvae of the two species a ppear to differ in their susceptibility to pond drying and predators. These differences may bely a trade-off between abilities to garner res ources and avoid predation, which contributes to segregation in larval distributions between Pseudacris species.