We observed rapid colonization of amphibians into restored wetlands and exponential growth in the number of populations following a large-scale ecosystem restoration. Within five years of beginning the restoration, all 10 species found on adjacent lands were breeding at Kankakee Sands. Our observation of a mean of 3.9 species per breeding site in 2003 compares favorably to a mean of 4.9 species of pond-breeding amphibians per wetland found at state fish and wildlife areas and nature preserves in the region (Brodman and Killmurry 1998; Brodman et al. 2002). We predicted that fossorial species and prairie species would colonize wetlands before other species. The data generally supported this hypothesis. Both prairie species (Western Chorus Frogs and Northern Leopard Frogs) and two of the three fossorial species (American Toads and Fowler’s Toads) were among the five species with the greatest number of colonizing populations (Table 1). The Spring Peeper also was among the earlier colonizing species, but the fossorial Tiger Salamander was slow to colonize.
These results are similar to those reported for restored wetlands on former agricultural lands in Minnesota (Lehtinen and Galatowitsch 2001). Lehtinen and Galatowitsch (2001) found that eight species of amphibians rapidly colonized restored wetlands. Restored wetlands had 67% as many species as nearby natural wetlands and the mean species richness per wetland was 71% as much in restored compared to nearby natural wetlands.
The species with the greatest increases in Minnesota were Western Chorus Frogs and Northern Leopard Frogs. Our observation that pond-breeding salamanders are slower than frogs in colonizing restored wetlands supports the findings of other studies (Lehtinen and Galatowitsch 2001; Pechmann et al. 2001).
Although many tadpoles survived through metamorphosis at most wetlands in 2002 and 2003, very few survived in 2001. Remnant ditches are important in keeping late-stage tadpoles and newly metamorphosed froglets from desiccating; however, several ditches harbor fish populations that entered restored wetlands during flooding events. Predatory fish can eliminate amphibians from isolated, small wetlands by eating eggs and tadpoles (Paton and Crouch 2002). Studies of isolated wetlands in Rhode Island suggest that few species have 95% of tadpoles metamorphose and emigrate from breeding ponds prior to 31 July, and that species using semi-permanent wetlands require inundation until mid-November (Paton and Crouch 2002). Maintaining water levels of restored wetlands through August (Paton and Crouch 2002) and keeping the wetlands fish-free are primary management concerns.
Species of frogs that were known to inhabit Kankakee Sands prior to the degradation of the sandy wetland habitat rapidly colonized the restored wetlands. Further study is needed to determine whether amphibian populations at restored wetlands are source or sink populations. There is potential for this community to increase further if source populations of Smallmouth Salamanders (Ambystoma texanum), Eastern Newts (Notophthalamus viridescens), Cricket Frogs (Acris crepitans), Crawfish Frogs (Rana areolata) and Plain’s Leopard Frogs (R. blairi) in adjacent counties are able to colonize Kankakee Sands. Additional studies are required to determine what, if any, barriers are preventing emigration of these species into the restored habitat of Kankakee Sands.
Acknowledgements.—We thank Jeanette Jaskula and Sarah Rock for conducting surveys in 2000. We thank Marissa Marlin for assisting us in making drift fences and conducting surveys in 2001, and Michael Oskorep and Adam Walker for assisting us in making drift fences and conducting surveys in 2002. We thank Adam Walker, Ryan Dorton, Randy Hoffman, Tony Kretz, and Shannon Finerty for conducting surveys in 2003. We thank Chip O’Leary for providing maps and giving advice. This study was supported and funded by the Efroymson Restoration Foundation and the Indiana Chapter of The Nature Conservancy.