The current knowledge on the herpetofauna of Syros is updated, whereby no publications on it have been made since 1975. I provide the results from a field trip in 2024 that focused on the hygrophilous species. The Balkan Water Frog and the Balkan Terrapin, mentioned for Syros in the 19^th century, meanwhile have become extinct. The Green Toad is threatened with extinction, the status of the Grass Snake is unclear. The Green Toad has benefited previously from anthropogenic spawning grounds in the form of open cisterns, which have fallen into disuse and thus are no longer available to the amphibians. The ongoing climate change in the Aegean region is reflected in drier winters, which dry out water bodies. The situation for the wetlands and their fauna and flora on Syros is alarming.

conservation, hygrophilic herpetofauna, status, wetlands

Syros, also known as Syra in older spellings, lies in the middle of the Cyclades Archipelago. Its area is 84 km², with Pyrgos peak reaching 442 metres above sea level. With its 21,500 inhabitants (2011), it is the most populous island in the Cyclades, and includes Ermoupoli, the administrative centre for the southern Aegean region. The island is divided into a largely uninhabited, treeless northern half (Fig. 1) and a more intensively used and urbanised southern half.

Figure 1. 

Largely uninhabited north of the island Syros with Phrygana and very dry.

There has been no dedicated study on the amphibians and reptiles of Syros, and no field herpetological results have been published on this island for almost 50 years. Bedriaga (1882) mentions the occurrence of the Balkan Terrapin (Mauremys rivulata) and the Balkan Water Frog (Pelophylax kurtmuelleri) on Syros. These were my incentives to visit the island and check for possible occurrences.

The first herpetological references to Syros go back to Theodor Erhard’s Fauna of the Cyclades (Erhard 1858). Bedriaga (1882, p.7, 14) describes Erhard’s contribution as erroneous; he is said to have confused species and islands in his work.

Fifty-six years later, Werner (1938) recorded eight species of amphibians and reptiles on Syros. He also adopts “Clemmys caspica” and refers to Bedriaga (1882). The most intensive herpetological work on Syros was done by Frör and Beutler (1980). The authors visited Syros in 1974 and 1977 and were able to evaluate additional herpetological collections (especially parts of Buchholz and Gruber and Fuchs collected materials, kept in the museums of Bonn, München and Vienna). Beutler and Frör (1980) provide an overview of the amphibians and reptiles found on the northern Cycladic islands (table 2 in their work). They consider the Syros herpetofauna to belong to the Central Cyclades. Overall, 13 species are listed in Beutler and Frör (1980) for Syros.

There were three of us on our daily excursions. We visited Syros from 3–16 April 2024 with an overnight stay in Kini (former Kinion) on the west coast. During our stay on the island, the weather was mostly sunny, with air temperatures around 18–21 °C in the daytime and around 8 °C at night, mostly windy but occasionally stormy. We visited the whole island by car and on foot. In Kini, the area was also searched at night for the Green Toad. Of the 13 species recorded on Syros, we were only able to identify six. Below I provide a species list, including references to published data and specific data from this field sampling.

A particular focus of our visit was the search for wetlands. Beutler and Frör (1980, p. 257) found no large wetlands on Syros. They found smaller bodies of water at Posidonia, Ghalassas and Ermopoulis. In the inventory of wetlands on Greek islands (WWF 2014), only two inventory objects are designated for Syros (Fig. 2). SYR 001 “Estuary of Varvaroussa Beach” is located nearby Kini (37.46861°N, 24.89694°E). On 12 April, only a remnant of a brackish backwater measuring approx. 10 m² was still present there (Fig. 3). SYR 002 “Ghalissas Bay” is located west-northwest of Ghalissas and should also include a brackish backwater on 1.18 ha (37.42083°N, 24.87777°E). During the site visit on 5 April, there was no surface water at all, only remnants of a reed bed were still present (Fig. 4). The wetland inventory protocols do not contain any further natural history information including about amphibians.

Figure 2. 

Map of Syros with indication of WWF objects wetlands and former and present occurrence of the Green Toad. Map source: WWF Greece 2014.

Figure 3. 

Estuary of Varvarousa Bay in WWF-Greece wetland inventory.

Figure 4. 

The former wetland in Ghalissas Bay as indicated in WWF-Greece wetland inventory.

The estuaries of somewhat larger catchment areas into the sea were specifically investigated, as were all the spring locations included in the Skai map (no. 305 Syros; scale 1:20 000). These were either captured or have dried up. We saw flowing water (a short open sewer that flowed into the bay) only in the southern industrial area of Ermoupoli

In the southern half of the island, the demand for water is high due to the intensive vegetable and horticultural plantations. No other Cyclades island has had such a dense network of cisterns and so many groundwater wells. However, many of the open cisterns are no longer in use. The groundwater in the wells, which are also no longer active, can be found at an estimated depth of 8–10 m.

In the summer months, the ecological system suffers under the drought. The influx of tourists temporarily doubles the population. Water consumption on Tinos increases from 1,500 cubic metres to an average of 2,700 cubic metres per person per day; the situation is similar on Syros. Drinking and processed water comes from the sea, 95% of which is treated in desalination plants. There is also a lack of infrastructure, such as piping, to utilise the purified water (Papasozomenou 2017).

Climate change effects are not manifested uniformly worldwide. In the Mediterranean, an increase in dry winters is noticeable (data from ERAS, fifth generation atmospheric analysis of global data, covering 1979–2021 with a spatial resolution of 30 km (www.meteoblue.com/de/wetter/archive/export/syros_griechenland2537; accessed on 9 Oct 2024).

The average temperature has increased by 1.6 °C. since 1979 (Fig. 5). The average annual precipitation in the period 1979–2023 was 289 mm. The years 1981, 2003 and 2019 were wetter but since 2020 it has remained consistently dryer (Fig. 6). During our stay on the island, we did not find any surface water in the dry streams that carry water during heavy winter rainfall. Water can usually be found in a normal year in siphons in rocky pools or as backwater at the mouths of the streams. These changes in weather have a massive impact on the hygrophilic herpetofauna, as has already been described for the island of Ios (Broggi 2023). The impacts are described below for two species of herpetofauna for Syros.

Figure 5. 

Mean annual temperature in Syros 1979–2021. The dashed blue line is the linear trend of temperature change. The stripes in the lower part of the graph indicate deviations from the mean, with blue for colder and red for warmer years (Data from: www.meteoblue.com/de/wetter/archive/export/syros_griechenland2537; accessed on 9 Oct 2024).

Figure 6. 

Annual precipitation in Syros 1979–2021. The stripes in the lower part of the graph indicate deviations from the mean, with green for wet and brown for dry years (Data from: www.meteoblue.com/de/wetter/archive/export/syros_griechenland2537; accessed on 9 Oct 2024).

It has been very dry in recent years, as confirmed by our own observations in 2024. We could not find available natural biotopes on Syros as spawning sites for Green Toads. Open cisterns are sometimes accessible for the reproduction of the Green Toad, as was shown for the Cycladic island of Kythnos (Broggi 2021). The numerous open cisterns on Syros have also been used historically as alternative spawning grounds by the toads

The three locations of the Green Toad in Kini, Ghalissas and Ermopouli mentioned by Beutler and Frör (1980) were searched (Fig. 2) intensively, especially during the overnight stay in Kini. At Kini only two open cisterns filled with water were found to be possible spawning sites for the Green Toad. However, Goldfish (Carassius auratus) were found in these tanks. The spawn of amphibians is eaten by the Goldfish, especially if there is no protection by vegetation. Goldfish were also found in several other cistern sites in the south of the island (Fig. 7). Benefits for people from these Goldfish are hard to conceive, whereas the harm to the amphibians is immense. Coexistence between fish and amphibians is possible, but depends on the presence of shallow water zones with riparian vegetation (Laufer and Wollenzin 2011). This is not the case with cisterns.

Figure 7. 

Open cistern with water but also Goldfish.

The intensive search for the Green Toad on 10 April led to an open cistern in the middle of Posidonia with a basin size of approx. 12 × 12 metres (37.38611°N, 24.88917°E). Well-developed tadpoles of the Green Toad were found in it (Fig. 8). This remained the only island record. Evidently, the Green Toad on Syros is threatened with extinction.

Figure 8. 

Cistern in Posidonia with tadpoles of Bufotes viridis (37.38611°N, 24.88917°E).

These general conditions also indicate why the Balkan Frog (Pelophylax kurtmuelleri), mentioned by Bedriaga (1882) as occurring on Syros, can no longer be found on the island. Beutler and Frör (1980) described the then current occurrence of the water frog as “questionable”.

There is only a reference by Bedriaga (1882) for the occurrence of the Balkan Terrapin on Syros, unfortunately, without providing a location. Beutler and Frör (1980) stated that the Balkan Terrapin “may already be extinct”. In the village of Hartiana in the north of the island on 7 April, we met two young Greeks with whom we struck up a conversation. They asked about our reason for visiting the island. When we asked about the possible presence of turtles, one of them surprised us by telling us that a friend had told him that he had seen turtles in a body of water in Sykaminia Bay below the hamlet of Kambos in the north of the island. He marked the possible location on the map, which was a few hundred metres above the bay. This made it impossible to confuse it with sea turtles. A search of the indicated location the following day gave no indication of such a possible habitat. Geologists encountered in the area confirmed that they had not seen any water surface in this area. How should this observation be interpreted? Was there still a relict population on the island in recent times? We cannot judge this, but believe that the location given is hardly possible for a long-standing water surface. From today’s perspective, based on our own research, there is a lack of suitable habitats for the terrapin on the island. Still, the extinction of the Balkan Terrapin must be confirmed for Syros.

Four conclusions can be drawn for the current state of the hygrophilic herpetofauna on Syros:

Figure 9. 

Abandoned cistern.

Figure 10. 

Historic groundwater well out of operation.

1. Wetlands are naturally rare on the small Cyclades islands of less than 100 km ² in size, as they usually lack larger hydrological catchment areas with water retention. Such habitats are usually only possible on a small scale, they are therefore vulnerable, very sensitive to external influences and the animal and plant species living in them are relictual in nature. Genetic exchange is hardly possible anywhere.
2. Due to their fragility, aquatic habitats are particularly at risk. For island wetlands, there are conflicts of use with agriculture and tourism. Agriculture is interested in suitable agricultural land where watercourses flow into the sea and has therefore cultivated wetlands. Agriculture development has utilised the watercourses that flow in winter and channeled the water through hoses into reservoirs and cisterns for irrigation of crops. Pumping also lowers the groundwater level. There is also a conflict of use in the estuary area of the dry streams with tourism, which is interested in utilising suitable sandy beaches.
3. While the natural habitats were impaired by increasing utilisation pressure, the hygrophilic herpetofauna was able to benefit in the past in part from the anthropogenic structures with the open cisterns. In the course of the ongoing structural change in agriculture, the maintenance of this complex irrigation regime is increasingly being dispensed with (Fig. 9). Groundwater pumps are being used or agricultural practices are being abandoned (Fig. 10). As a result, these sub-optimal habitats are no longer available. Goldfish stocking in cisterns presents a further threat.
4. Climate change is noticeable through marked increases in temperature, but also manifests itself in drier winter months with a lack of the usual heavy rainfall. This contributes to a massive reduction in suitable habitats and prevents amphibians from reproducing. In the Cyclades elsewhere, amphibians such as the Balkan Water Frog (Pelophylax kurtmuelleri), the Green Toad (Bufotes viridis), the Common Toad (Bufo bufo) and the Tree Frog (Hyla arborea) are particularly affected. Among the reptiles, this also applies to the Balkan Terrapin (Mauremys rivulata), the Grass and Dice Snakes (Natrix natrix and N. tessellata) and, to a lesser extent, the Nose-horned Viper (Vipera ammodytes) and the Giant Green Lizard (Lacerta trilineata), which also prefer more humid structures.

I thank my two travelling companions Dr. Peter Goop (Vaduz), and Mag. Günter Stadler (Frastanz), for their valuable assistance during the natural history excursions. A big thank you also goes to the reviewers of this contribution.