Advisor: Günter Gollmann
Master's Defensio - Friday, March 27th 2026, 9:45
Seminarroom 1.4, UBB, Djerassiplatz 1, 1030 Vienna
Abstract
The European green toad, Bufotes viridis, is often found in urban areas. This pioneer species is highly adaptable and quickly colonizes newly created habitats, e.g. artificially created ponds or gravel pits. Despite its adaptable way of life, the populations of B. viridis are declining throughout Austria. This capture-recapture study investigates a population of B. viridis in Simmeringer Haide (Vienna, Austria) and compares the results with data from three previous years.
Two artificial breeding sites were investigated, which are typical locations for B. viridis: a concrete pool and an artificial rainwater collection basin. Data were collected between March and August 2023, on average twice per week. Capture-recapture data were collected by taking pictures of the toads’ individual dorsal pattern and individuals were identified using the semi-automated pattern recognition software IBEIS.
The snout-vent length and body mass of each individual were recorded to calculate the scaled mass index in order to assess the body condition of the population. The exact location and sex were recorded as well. For the analysis of estimated population size, detection probability and apparent survival probability, the Jolly-Seber-Schwarz-Arnason open population model was used.
In this study 650 individuals were captured during the breeding season in 2023, including 581 males and 69 females. A total of 550 toads (85%) were caught for the first time, 100 toads (15%) were recaptures from the previous years. The population size was estimated to be 1883 individuals (CI: 1574-2254) and the calculated scaled mass index was 21.8 (CI:0.68). The apparent survival probability from 2022 to 2023 was 49% for females (CI:30-68) and 41% for males (CI: 34-49).
Compared to previous years, the apparent survival probability and the estimated population size increased. Continued long-term monitoring and the expansion of surveys to additional breeding sites and terrestrial habitats are recommended to create a further data basis for the future protection of the green toad and to prevent the disappearance of further green toad populations in Vienna's urban area.
