PS 34-217 - Critical Steps for Imperilled Amphibian Reintroductions

Abstract: Declines in amphibian populations led to the implementation of conservation breeding programs (captive breeding and reintroduction) to prevent their extinction. However, the success of these programs is largely contingent upon the survival of the released tadpoles or metamorphosed individuals, making it imperative to assess the suitability and quality of the habitat before reintroduction. This study focuses on two threatened amphibian species in Canada, the Oregon spotted frog (Rana pretiosa, OSF) and the Northern leopard frog (Lithobates pipiens, NLF), and highlights the importance of conducting ex-situ survival experiments along with environmental and contaminant screening before reintroduction. Since monitoring the survival of tadpoles after reintroduction is challenging, rearing tadpoles in site water in a controlled laboratory environment can provide insights into the post-release survival of tadpoles. The Organisation for Economic Co-operation and Development (OECD) has guidelines for testing chemicals on Larval Amphibian Growth and Development (Test 241: LAGDA). Using this test, we can determine the potential effects of site water on re-introduced OSFs or NLFs. Additionally, environmental contaminant screening can be performed to quantify water and sediment contaminant concentrations at reintroduction sites. This information can comprehensively assess habitat quality beyond current habitat assessments and provide valuable insights into potential contaminants that could negatively impact growth, development, and reproduction. Currently, we provide data for NLF sites and are waiting for data analysis on the OSF reintroduction site. All surface water of NLF critical habitats had total and dissolved magnesium concentrations above the United States Environmental Protection Agency (US EPA) guidelines (0.647mg/L). Furthermore, all sites, except for one, had total iron levels exceeding the Canadian Council of Ministers of the Environment (CCME) Water Quality Guideline (WQG) (0.3 mg/L). Total aluminum concentrations at one site also exceeded the CCME WQG (100 mg/L adjusted for a pH of 10.1). Additionally, total iron and sulfur concentrations in sediment exceeded CCME Sediment Quality Guidelines (SQG) values in suspected NLF overwintering locations. These metal contaminants have evidence of decreasing the hatching success and survival of developing amphibians. In conclusion, this study advocates conducting ex-situ development and survival experiments and establishing standardized environmental contaminant screening protocols at OSF and NLF reintroduction sites. By doing so, we can minimize or avoid the potential impacts of contaminants on growth, development, and reproduction. These changes can enhance the efficacy of these critical conservation efforts and help to ensure the long-term survival of these threatened amphibian species in the wild.