Re-introduction program for the common midwife toad and Iberian frog in the Natural Park of Peñalara in Madrid, Spain: can we defeat chytridiomycosis and trout introductions?

Summary

The common midwife toad, endangered in Madrid, and the Vulnerable Iberian frog both declined severely in Spain's Penalara Natural Park, the toad from a chytrid fungus outbreak in the late 1990s and the frog from introduced brook and brown trout that eliminated it from most breeding ponds. Spain's National Museum of Natural Sciences with the Durrell Wildlife Conservation Trust began collecting midwife toad tadpoles from across the park in 2006, treating them for chytrid infection with elevated temperature and antifungal drugs, rearing them to adulthood indoors, and releasing most back at their capture sites while retaining some for a captive colony guided by microsatellite genetic analysis to preserve variability lost to a population bottleneck. Iberian frog eggs and tadpoles were collected from a stream that naturally dries before larvae can fully develop, head-started in 80-liter tanks, and released into streams cleared of trout after nine years of electrofishing eradication effort. Early releases targeted a pond that dries seasonally to reduce chytrid persistence, since treated toads still become reinfected on contact with the fungus in permanent water. In the most recent season, over 180 midwife toad tadpoles were produced in the rearing center, released metamorphs of both species survived nearly a full winter, and for the first time complete midwife toad reproduction, from calling males through tadpoles, was recorded from released animals, while some previously released Iberian frogs were also relocated. The project rates itself Partially Successful, citing this progress against the ongoing challenges of chytrid infection and trout recolonization.