Estimation of green toad Bufotes viridis population size based on photo-identification at two urban sites with different management histories

Individual recognition during fieldwork is necessary when estimating the size of a population for conservation or
management purposes. We used a non-invasive method of individual photo identification based on dorsal color patterns. Our study
aimed to estimate the size of two green toad Bufotes viridis populations in an urban habitat to provide input for conservation
activities. The study was conducted in the two largest known breeding sites of the species in Poznań, Western Poland: Cytadela
Park (PC) and Rataje Park (PR). We collected animals within each site’s breeding habitat twice during the mating season. Dorsal
pattern photographs and morphometric measurements were taken, after which the animals were released immediately. We
analyzed the pictures by single-eye matching to estimate the population size using the Chapman estimator. Most individuals caught
were males, and no females were recaptured. Therefore, we used only data for males and then estimated the total population size
based on a calculation using the sex ratio known from the literature. The number of captured toads was higher at the PC site than at
the PR site. Toads from the PC population were noticeably larger and had higher condition value indices than those from the PR
population. This result is consistent with the management and history of both sites. We observed habitat transition and potential
mortality due to park construction the year before our study at the PR site. In contrast, the PC site is a mature green area with more
than 50 years of stable management. Despite some limitations, photo-identification may be an essential first step in estimating
population size in community-based conservation initiatives for the green toad, enabling conservationists to enter the public
discussion about urban conservation, providing a reference for the conservation value of urban breeding sites, and as a
consequently, providing input for active conservation and habitat management (e.g., fish removal and mowing regime
modifications).