Evaluating the quality of created wetlands through metamorphic amphibian sampling

Background/Question/Methods

Habitat alteration in the United States has led to the destruction of many wetlands through draining or filling. In recognition of the loss of wetlands, the United States government has implemented policies that require any lost wetlands be replaced with created or restored wetlands. However, a central question that remains is whether a created wetland replaces the ecological function of the lost wetland. Ecological function of created wetlands can be assessed through monitoring of breeding adults, larval stages, and metamorphic juveniles of amphibians. Metamorphic juveniles are especially important because they represent the primary dispersal stage that help maintain populations, re-establish locally extinct populations, and establish new populations. Complete drift fences with pitfall traps were constructed around four wetlands (1 natural, 3 created) to sample metamorphic amphibians and compare abundance, size, and weight to evaluate the quality of natural and created wetlands.

Results/Conclusions

Abundance, size (snout-vent length), and weight of metamorphic amphibians varied between the natural and created wetlands. Metamorphic Green Frogs (Rana clamitans) showed significant differences in size (p <0.001) and weight (p < 0.001) between the created and natural wetlands. A significant difference of size (p < 0.001) and weight (p = 0.029) of Green Frogs was also found among the created wetlands in which they were captured. Silvery salamander (Ambystoma platineum) metamorphs were exclusively captured at the created wetlands. Excluding the third created pond because of the low capture numbers, a significant difference in size (p = 0.001) and weight (p = 0.008) was found among the created wetlands. The number of individuals captured (for both Green Frogs and Silvery salamanders) was inversely proportional to both size and weight. The natural wetland was the only wetland that included both metamorphosing Green Frogs and Southern Leopard Frogs; however Silvery Salamanders were absent. The inverse relationship between metamorphic abundance and metamorphic size and the availability of created wetlands as a refuge when a natural wetland has become unsuitable for reproduction show that re-creating a diversity of wetlands across the landscape may benefit some wetland breeding amphibians.