Amphibian occupancy and habitat use in a system of restored wetlands

Emily A Stulik, Purdue University

Abstract

Amphibians are of great conservation concern due to alarming population declines worldwide. Their unique and specific biological needs make them especially sensitive to environmental changes. These vulnerable ectotherms are threatened by habitat loss and degradation, especially in the Midwestern United States. In Indiana, loss of over 85% of the state’s natural wetlands has resulted in multiple species declines, including two species of special concern, the Northern Leopard Frog, Lithobates pipiens, and the Blanchard’s Cricket Frog, Acris blanchardi. Fortunately, efforts to restore wetland habitat can mitigate some aspects of habitat loss, but effective sampling techniques and suitable analytical approaches are needed to accurately measure the quality and functionality of the restored habitat. Occupancy and habitat use of amphibians inhabiting a 716 acre restored wetland system in Fort Wayne, Indiana was measured in 2013 and 2014 to assess restoration status and habitat quality. Two types of survey methods—call surveys and tadpole surveys—were used to compare amphibian presence and absence among the different wetlands in the preserve. Most species occupied both established and restored wetlands, with the exception of the Unisexual Ambystoma Salamander and the Small-mouthed Salamander, which only bred in forested, established wetlands. Habitat use was species–specific and largely driven by species biology. The two species of special concern had opposite responses to the restoration. Colonization and reproductive success was highest in the Northern Leopard Frog, while occupancy of the Blanchard’s Cricket Frog remained low. However, Blanchard’s Cricket Frogs colonized the restored wetland complex for the first time in 2014. In general, occupancy of larval amphibians in 2014 was low. Method comparison revealed that for the majority of species, occupancy of calling males did not accurately predict occupancy of tadpoles. Management decisions may be best suited to focus on wetlands where species are successfully reproducing, and not solely on where they are heard calling. Special attention should also be given to promoting and maintaining shallow ponds with short hydroperiods, as these ponds supported higher species richness and occupancy probability of tadpoles. These ponds were also the first to dry, often before successful metamorphosis was reached. While the extension of pond hydroperiod can ensure complete metamorph development, continued, long term monitoring of occupancy trends and reproductive success is essential to recommend sound management practices. Results of this baseline study reveal that Eagle Marsh Nature Preserve supports a viable and diverse amphibian community, and its restored wetlands can function in promoting occupancy and colonization of rare and declining species.

Degree

M.S.

Advisors

Kingsbury, Purdue University.

Subject Area

Ecology|Conservation biology

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