Biology session

Formerly the Hungarian meadow viper (Vipera ursinii rakosiensis) was present in the Carpathian Basin in large numbers, but today most of its habitat is gone and the handful of native populations survived only due to nature conservation. Despite actions of species protection in the last two decades, the viper’s density has not grown significantly. One of the reasons for this is presumably predation pressure. The basis of prey-predation relationships is an evolutionary race, in which the goal is to adapt to each other, for instance in activity. A previous study has stated that another viper species does not thermoregulate actively in a certain time interval when the circumstances are satisfactory, but the bird of prey activity is high, which is supposedly a predator-avoiding strategy. In this study our goal is the direct observation of viper-predation, and examining the overlap between the Hungarian meadow viper’s predicted and the possible avian predators’ daily observed activity. In the case of abundant bird species and the reptile-specialist short-toed eagle (Circaetus gallicus) we also make this comparison separately. The birds of prey survey took place in both main habitats of the Hungarian meadow viper in the Kiskunság, in five separate areas, in May and September, for 3 days each seasons. There were 2 observers in every area, from 7 am to 6 pm. The avian predator activity was modelled after the temporal distribution of this data, while the activity of the viper was modelled from the operative temperature of observations of living viper individuals (n=122) from the years 2020 and 2021. By the end of the avian predator observation we registrated 2075 observations from 23 species, from which two specimens was seen consuming meadow vipers. The predicted viper activity is of normal distribution with a mean of 27.5 °C, which indicates when vipers are the most active. Comparing this with the aggregated activity of birds, we found that the overlap between them was considerable in both habitats and seasons (delta≈0.7), with changing peaks of activity in the case of birds of prey. Between the separately examined bird species the common buzzard (Buteo buteo) in autumn season had the biggest overlap in activity with the viper (delta=0.85), and the short-toed eagle in spring, in only one habitat had the smallest (delta=0.33), which might be only because of their low number of individuals in the area. In conclusion we were unable to display definite predator-avoiding strategy by comparing activitiy patterns between avian predators and the Hungarian meadow viper. Still it is important to mention that the days of the predator survey were unusually cold and rainy, which was not as effective in thermoregulation-based modelling of the viper’s activity as average weather would have been. Repeating the observation next year might show us different results as well as predicting the activity of the viper based on the temperature of a longer time interval.