The Natterjack Toad

Conservation of pioneer species in a lignite mining area in central Germany


Project description


Opencast lignite mining creates important secondary habitats for a large number of pioneer species specialised on highly dynamic environments. As lignite mining in Germany runs out within the next two decades, these habitats are increasingly lost due to succession and recultivation of subsequent landscapes. In central Germany, the natterjack toad is one of the species that particularly dependent on opencast mining. Like many other pioneer species, its population has declined sharply in recent decades. Studies focusing on natterjacks in opencast lignite mines areas are rare, so underlying limiting environmental factors in these important habitats are barely known. We investigate natterjack toad populations in a model region in the south of Leipzig to be able to preserve them beyond the end of mining. In the study region, spawning waters and terrestrial habitats of different types are populated, including active coal mining sites or adjacent pastures in recultivated areas.

Project goals

In our project we focus on aspects that have been identified as key demographic factors of natterjack toad populations inhabiting other habitat types and regions. For the aquatic life stage, we aim to identify water bodies corresponding to the toads habitat preference while offering a low risk of desiccation and high metamorphosis rates. In the terrestrial habitat, the ecology of juvenile and subadult toads are in focus. The survival of juvenile anurans is particularly important for the stability of local populations, and migrating juveniles are primarily responsible for the genetic exchange and the support of neighbouring populations (functional connectivity). We investigate how habitat structures and microclimate drive the spatial ecology of juvenile natterjack toads. Thereby, conservation measures targeting functional connectivity, such as stepping stone habitats, can be optimized. 


According to the long period of reproductive activity in natterjack toads, potential spawning waters are surveyed in a 2-week cycle from April to July. The habitat characteristics, water level dynamics and abundance of larvae and spawn are recorded. The space and habitat use of juveniles is investigated by actively searching standardised plots in which ground temperature and humidity are recorded. Besides, juveniles of a minimum size are individually sampled using photographs of their ventral and dorsal sides. Using occupancy models, the probability of detection of spawn, larvae, and juveniles, which can vary according to habitat characteristics, can be accounted for. In addition, the habitat-specific density in the terrestrial habitat is determined using spatial-capture-recapture models.