Frames of seasonal activity and the reproductive phenology of two species of anuran amphibians (Anura: Bufonidae; Hylidae) of the Karadag Nature Reserve in Crimea

Abstract

Background. The current climatic trend towards warming and aridization has a negative impact on amphibian populations on a global scale. Against this background, longterm monitoring the time frame of life cycle phases and the dynamics of abundance in local amphibian populations become highly relevant. Territories located at the junction of different landscape-climatic zones, where general patterns should emerge most clearly, are gaining great interest in this vein. The purpose of the research is to study the seasonal patterns of activity and time frames of the reproduction in populations of the Green Toad (Bufotes viridis) and the Eastern Tree Frog (Hyla orientalis) and also the detection the relationship of the timing of seasonal phenomena with local climate and observed weather conditions. Materials and methods. The work was carried out in 2002–2023 in the Karadag State Nature Reserve. The data about the life cycles of amphibians is based on year-round stationary observations. To assess the strength and character of the relationship between phenological phenomena and climatic indicators of the area (according to the data of meteorological station near Biostantsiya settlement), correlation analysis was used. Results. A generalized trajectory of populations of two common amphibian species at the beginning of the 21st century was presented and the data about the phases of their life cycle has been updated. Some phenological phenomena correlate with climatic parameters at a statistically significant level; in many cases, a relationship at the trend level was found. For both species, a shift in the timing of phenological phenomena associated with a change in the moisture regime of the territory of the Karadag reserve, was recorded. The predominance of little snow winters and dry springs against the backdrop of rising temperatures has led to the degradation of spawning reservoirs. The duration of the spring spawning phase has decreased, but the duration of its “summer” phase, coinciding with periods of heavy rainfall in May – July, has increased compensatoryly. Conclusions. Despite the flexibility of the time frame of reproduction in the studied species, aridization of Karadag’s landscapes which has been continuously increase since the mid-2000s, caused a catastrophic decline in the amphibian abundance. Practical measures for the conservation of anuran populations on protected territory are proposed.

Keywords

• green toad
• eastern tree frog
• summer spawning
• mesoclimate
• aridization
• mediterranea