Golem Grad is a small but ecologically and culturally significant island in Lake Prespa, known for its rich and unique biodiversity, as well as for millennia-old archaeological remains of past human settlements. Today, nearly a century after its last human resident, the island has become a “town” inhabited by a multitude of plants, insects, birds, and – of course – reptiles.
Due to the historically large population of dice snakes (Natrix tessellata), the island is popularly known as the “Snake Island,” drawing the attention of herpetologists for decades. Additionally, the island is also home to the elusive horned viper (Vipera ammodytes), although in smaller numbers. However, both experts and locals have observed that snake numbers have noticeably declined compared to the past.
To assess the current status of Golem Grad’s snake populations and their role in the island’s delicate ecological balance, experts from the Macedonian Ecological Society, in collaboration with colleagues from the Faculty of Biology in Belgrade (Serbia) and the Centre for Biological Studies in Chizé (France), conducted a regular field monitoring of snakes and other reptiles.
Using non-invasive capture-and-mark methods, the teams collected valuable data on species condition, population numbers, behavior, and various ecological parameters.
According to initial findings, the dice snake population has declined dramatically compared to the late 2000s and early 2010s, when it was estimated at nearly 25,000 adult individuals. Today, that number is down to just over 5,000. This decrease is likely due to fishing nets set around the island, in which the snakes easily drown. Unfortunately, such nets are still commonly used. A new management plan for Lake Prespa outlines a strict protection zone in the waters around Golem Grad, mirroring the zoning already in place on the island as part of Galichica National Park. There is hope that enforcement of restrictions in this zone will soon become more consistent.
Nevertheless, in the past three years, field observations suggest a slight recovery of the dice snake population. This trend remains to be confirmed through ongoing monitoring and data analysis. Experts suspect that the improvement may be partly due to better fishing regulation in neighboring Albania, as well as a shift from fishing with fine-mesh nets targeting Prespa bleak to larger-mesh nets used to catch carp – nets that dice snakes can more easily avoid.
In contrast, the horned viper – leading a hidden life in the island’s interior – has not shown signs of decline. Its population has remained stable, with standard adult population fluctuations between 200 and 300 individuals over the last 19 years.
It’s important to emphasize that these are preliminary findings for this year. Detailed laboratory analysis of the collected data will follow after the field season ends. This kind of activity is essential for developing effective conservation strategies, deepening our understanding of Golem Grad’s ecological dynamics, and raising public awareness about the vital role snakes play in the broader ecosystem.
These efforts are part of the project “PrespaNET III – Conserving Biodiversity in Transboundary Prespa”, supported by the Prespa Ohrid Nature Trust (PONT), the Aage V. Jensen Foundation, and EuroNatur.
