Amphibian response to wetlands in restored and reclaimed grasslands: Passive recolonization and active reintroduction techniques.

摘要

Amphibian declines are occurring globally with one-third of species expected to face extinction over the next few decades. Numerous strategies are being developed to conserve amphibian species, including Amphibian Ark's assurance colonies (captive populations), captive-breeding, captive-rearing, and specific habitat modifications to ensure survival of populations and persistence of species. These efforts are time consuming and expensive, and success is not guaranteed. Because amphibians carry little economic or emotional clout, the most effective way to conserve these animals, across much of North America, is to conserve or restore the ecosystems they inhabit. Restorations and reclamations re-create habitat that support passive recolonization of amphibians without additional, expensive intervention. To explore the ability of post-agricultural and -industrial landscapes to support amphibians, I studied amphibian occupancy and behavior on grassland-wetland assemblages in two sites---northwestern Iowa and southwestern Indiana. In Chapter One, I provide an overview of grassland, wetland, and amphibian losses in North America in order to establish a framework for these imperiled habitats and their amphibian components. In Chapter Two, I detail my survey of 130 prairie pothole wetlands restored over the past 50 years in the Okoboji lakes region of Iowa. I sampled for larval amphibians using a removal design in 2012 and analyzed occupancy with PRESENCE models. Wetland basin size, age (years since restoration), and presence of fishes and a non-native amphibian (American Bullfrogs [Lithobates catesbeianus ]) influenced passive recolonization by native amphibians (Northern Leopard Frogs [L. pipiens] and Eastern Tiger Salamanders [Ambystoma tigrinum]). In Chapter Three, I examine the response of an Indiana state endangered anuran (Crawfish Frogs [Lithobates areolatus] to weather variables related to climate change using wildlife camera photos (n = 694,786; taken around-the-clock over the course of five years) of frogs active outside their burrows in 2009--2013. At the study site, Hillenbrand Fish and Wildlife Area-West (HFWA-W, Greene County), Crawfish Frogs passively recolonized following surface coal mining in 1976--1982 and subsequent grassland reclamation. I found that Crawfish Frogs were active throughout the year, with peaks in activity in the late spring and early fall. Additionally, frogs shifted from crepuscular during the winter to diurnal during the high activity peaks to nocturnal during the mid-summer lull in activity. These results suggest anurans can adapt behaviorally to fluctuating weather conditions as climate change progresses, even on restored landscapes. Finally, in Chapter Four, I assess the feasibility of captive-rearing and release of Crawfish Frogs for situations where active reintroductions would be beneficial. Each year from 2013--2015, I sent eggs to Detroit Zoological Society, where my collaborators reared tadpoles to a late larval stage and then returned these animals to HFWA-W. Tadpoles completed development in aquatic mesh cages, and upon metamorphosis, I processed, marked, and released juveniles nearby in the prairie uplands. With survivorship nearly 70% during the final year, I recommend captive-rearing techniques for Crawfish Frogs that may contribute to a large-scale active reintroduction effort across this imperiled species' range. Even in areas where amphibians are not the primary focus, habitat restorations and reclamations can indirectly benefit and support passive recolonization of native amphibian populations.