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Review Article
Occurrence and status of the European Pond Turtle, Emys orbicularis hellenica (Valenciennes, 1833), on Aegean and Ionian Islands (Greece, Turkey)
expand article infoMario F. Broggi‡
‡ Unaffiliated, Vaduz, Liechtenstein

Corresponding author: Mario F. Broggi ( mario.broggi@adon.li )

Academic editor: Günter Gollmann
© 2023 Mario F. Broggi.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation: Broggi MF (2023) Occurrence and status of the European Pond Turtle, Emys orbicularis hellenica (Valenciennes, 1833), on Aegean and Ionian Islands (Greece, Turkey). Herpetozoa 36: 249-257. https://doi.org/10.3897/herpetozoa.36.e106864
ZooBank: urn:lsid:zoobank.org:pub:6380721C-8527-483C-A2F9-75E4E394635A
Open Access

Abstract

A study on the occurrence of Emys orbicularis in the Aegean, published in 2012, is here extended to the Ionian Islands. For the first time, a status analysis has also been carried out for the individual islands. Emys orbicularis is found on 11 Greek islands and one Turkish. Its presence on the big islands of Rhodes and Chios has not been ascertained so far, while for four previously mentioned islands there is no confirmation. On Corfu and Lesbos there are still viable larger Emys populations. Most other island occurrences are characterized by small populations. On Kefalonia, Zakynthos, Thassos and Samos, E. orbicularis is in danger of extinction because the wetland biotopes are threatened. In the meantime, many wetlands have been placed under protection. The enforcement of these nature conservation regulations needs to be monitored, and E. orbicularis can be a lead species for such monitoring.

Key Words

conservation, Emydidae, Insular Greece, Reptilia, Testudines, threats

Short portrait of the species

Emys orbicularis occurs in freshwater habitats, with a range extending from the Maghreb over the Iberian Peninsula, southern France and central Europe to the Baltic States, and in the south over Italy, the Balkan peninsula and Turkey to the Caspian Sea (Fritz 2001). In this large distribution area, a number of different subspecies are described. In Greece, the Eastern Mediterranean Emys orbicularis hellenica (Valenciennes, in Bibron and Bory de Saint-Vincent 1833) is described (Fritz 1998). This subspecies is small to medium-sized and its carapace is relatively high and narrow, with a usual maximum length of 25 cm. Its plastron is yellowish (Fritz 2001). The only similar species in Greece is the Balkan Terrapin Mauremys rivulata (Valenciennes, 1833), from which E. orbicularis differs in neck colouration pattern – striped in M. rivulata, spotted in E. orbicularis. Emys orbicularis lives in still or slow-flowing water in the shore area of lakes, ponds and ditches. Also, along the Mediterranean coasts, it is found in slightly brackish water in the backwaters of estuaries. Dense vegetation with a muddy substrate is preferred. It feeds mostly carnivorously, on snails, crustaceans – in fact, virtually anything it can catch – but will also eat aquatic plants (Fritz 2001).

Suitable habitats on the islands are similar to those on the mainland except that I never saw E. orbicularis in streams at higher altitudes. However after observations, it is noticeable that it only occurs on the peripheral larger islands along the continental shelf. There, M. rivulata and E. orbicularis usually live in the same habitat, thus sharing it sympatrically (Fritz 2001). Mauremys then shows itself to be in the majority, perhaps with the exception of Corfu. Emys also demands in my estimation less polluted waters than Mauremys and is less tolerant of salinity. It is striking that Emys on the Greek islands – contrary to the mainland – has not been observed by me in flowing streams and seems not to use them as a refugial habitat, unlike Mauremys. Their occurrences are concentrated in the lowlands, especially on the estuaries of water flowing into the sea with their network of hydrological structures.

Exploration on Greek islands

Herpetological research on Greek islands goes back almost 200 years. This begins with the Excursion de Morée in 1828–1833, which was a French military action in the Peloponnese as part of efforts for Greek independence. This military action was accompanied by a natural science commission under Bory de Saint-Vincent with 17 experts, including Gabriel Bibron, who was active in herpetology (Pafilis 2010). Werner (1938) and Wettstein (1953) made significant progress in herpetological research on Greek islands in the 20th century. The history of such research in Greece is described by Pafilis (2010). Valakos et al. (2008) present the amphibians and reptiles of Greece with distribution maps, which give us a good overview, as do Lymberakis et al. (2018) in a shorter contribution.

How does this present itself for E. orbicularis in particular? In the course of herpetological research in Greece, the Ionian Islands were initially the focus of attention. They were perhaps easier to reach for central European herpetologists, and they already belonged to the Greek state, in contrast to the islands of Asia Minor. The Cyclades then became the focus of herpetological research in the 20th century. However, no Emys orbicularis have been recorded there. In the Aegean, records are restricted to the larger peripheral islands on the Anatolian side, which were not the focus of the Austrian studies by Werner (1938) and Wettstein (1953). Another reason for late records is that E. orbicularis associates with M. rivulata and is less conspicuous, with its smaller populations, among Balkan Terrapin. This was at least the case for the observations by the author during the field research on Lesbos and Samothrace. It could also be true that for many field herpetologists the snake and lizard species are more in the foreground of consideration, and therefore the habitats of pond turtles were less well searched.

Occurrences on Greek islands and on Gökçeada (Turkey)

In the following, an overview of Emys occurrences on Aegean and Ionion islands (Fig. 1) is given in alphabetical order. A question mark appears against islands where a past occurrence is questionable. In each case the first description is mentioned, and further later observations from the literature are evaluated. Likewise, my own observations recorded in the field books of the excursions were included. As far as possible, the Emys orbicularis status on each individual islands is also described. This present contribution is the continuation of studies published in 2012, which referred only to the Aegean Sea (Broggi and Grillitsch 2012). Also in 2012, the species M. rivulata, which is sympatric with E. orbicularis, was dealt with for the Aegean (Broggi 2012). This study has now been updated (Broggi 2023).

Figure 1. 

Occurrence of Emys orbicularis on Aegean and Ionian Islands in categories present and question mark absent/status unknown. 1. Corfu; 2. Lefkas; 3. Kefalonia; 4. Ithaca; 5. Zakynthos; 6. Euboea; 7. Thassos; 8. Samothrace; 9. Gökçceada; 10. Lemnos; 11. Lesbos; 12. Chios; 13. Andros; 14. Tinos; 15. Mykonos; 16. Samos; 17. Kos; 18. Rhodos.

Andros? (380 km 2)

Bedriaga (1882) referred to Erhard’s “Fauna of the Cyclades” (Erhard 1858) in his overview of the amphibians and reptiles of Greece with the following statement: “Erhard has seen Emys on Naxos, Amorgos, Andros and Mykonos. I suspect that Erhard rather confused Clemmys caspica ssp. orientalis with Emys orbicularis.”. Werner (1938), therefore, does not take Erhard’s statement into account. Mauremys occurs today on the above islands, except Amorgos. After my visit to Amorgos in 2006, an earlier record of M. rivulata on that island is assumed to be rather unlikely (Broggi 2007). According to Fritz (1992), a colonization axis of Andros-Tinos-Mykonos would be possible in principle. Corresponding habitats would also be available. However, apart from the reference for Mykonos, which is to be confirmed, there are no indications of past or present Emys occurrences on these islands. Our intensive search on Andros in 1995 was also fruitless (Broggi 1996). I do not believe in the Andros-Tinos-Mykonos colonization axis for Emys orbicularis.

Chios? (843 km 2)

While there are Emys records for Lesbos and Samos, this is not yet the case for Chios. The herpetological contributions by Tsunis and Dimitropoulos (1995), Kasapidis et al. (1996) and Cattaneo (2003) do not provide any information in this regard. In Kasapidis et al. (1996), a distribution overview of Emys on the North-Eastern Aegean islands is published but without reference to Chios. I visited the island in 1991, without any Emys record, but with some Mauremys observations. Is it just that a record for Chios is still missing, or does Emys really not occur here? A possible occurrence is to be expected.

Corfu (Kerkyra) (585 km 2)

Werner (1894) mentions the occurrence of Emys on Corfu, which is probably the best herpetologically researched Greek island, including turtles (see Stille and Stille 2017). Wütschert (1984) reported that in the central part of the island Emys orbicularis is 9–10 times more common than Mauremys. He calls it widespread – in a pond near Tebloni in central Corfu he saw 150 specimens. Mertens (1960, 1961), on the other hand, described it as less common than Mauremys. In any case, the ratio between the two species is nowhere else on the Greek islands as balanced as on Corfu. Kattinger (1972) mentions E. orbicularis several times, for example on 3.8.1965 in a stream on the coastal plain, flowing from a walled well to Lake Korission; on 5.8.1965 several specimens there; and on 21.8.1965 several Emys orbicularis were seen among Mauremys rivulata in a stream in the lower reaches of the Sutoria. Toth et al. (2002) give an overview of Emys occurrences on the island. They also refer to other sightings: at Linia, Lake Korission (Kattinger 1972), Temblisi (Gundke 1988), Paleokastritsa (Werner 1894; Wütschert 1984), the Sidari region (Mertens 1960; Gundke 1988; Fritz 2001). Larger occurrences are mentioned several times for the Antinioti Lagoon and Lake Korission. Wilson (2014) mentioned Emys in his Corfu report for 2014.

There are also numerous photographic descriptions of trips, for example by Balej and Jablonski (2006, 2021) with sites at Acharavi 10.5.2007 and 2.8.2009; Agios Georgios 6.8.2011 and 8.5.2014; Ormos Ermones (38 m above sea) 13.8.2011 and 8.5.2011; as well as Stroggili 10.8.2011 and 8.5.2011. Kalter (2013) mentions for his trip in July 2010 five different sites with Emys orbicularis, three of them in small rivers and two in marshes and standing water. Some travel reports, among others by Vandenbroeck (2014), can also be found on the webpage of fieldherping.eu, where Emys is mentioned in a river near Agios Georgios, as well as in a pond near Sidari, which has as many as three species of water turtle, namely Emys, Mauremys and the invasive Red-eared Slider Turtle Trachemys scripta. The most recent report is by Speybroek (2022) covering an excursion from 10–17.4.2022. Emys cannot normally be seen in flowing water on Greek islands, so the above are exceptions, but probably the water was very slow flowing. Lake Antinioti, with about 40 hectares in the north of the island, is called “heaven for turtles”. It is located between the beaches of Almyros and Agios Spyridonas. Emys is, therefore, widespread on Corfu and has suitable habitats here to ensure its survival. It probably has a larger population here than on any other Greek island. Nevertheless, Stille and Stille (2017) consider E. orbicularis to be highly endangered on Corfu.

Euboea (Evia) (3,660 km 2)

In Boettger’s (1891) overview of the reptiles of Euboea, E. orbicularis is not yet listed. Cyren (1935) mentioned the species on the island for the first time. He saw some M. rivulata and an E. orbicularis in brackish water on the beach in the north of the island, the latter having a necrosis on its dorsal shield. He wondered if this was caused by the brackish water. Cyren (1941) mentioned again that he had captured, in brackish water, an E. orbicularis that had a dorsal carapace badly affected by algae. Werner (1938) refers to Cyren (1935) for his cited occurrence on Euboea. There are no later herpetological contributions with further Emys references, but there are individual references such as in Fritz (2001), and in Moysiadis and Efthimiou (2012), on a Natura 2000 object sheet GR 2420004, at Megalo Livari in the north of Euboea. Emys photos are also known from the island, for example by Davranoglou (2020) on a beach near Profitis Ilias. The status of this species on the island is thus not clarified; we can only state here that it does occur.

Gökçeada (Imbros) (279 km 2)

The first record was from the estuary of a stream near Aydmerk on 29.4.1998 (Fig. 2), then on 5.5.1998 and in a residual pond two kilometres away on 6.5.1998 on the east coast see location map in Broggi (1999). Bayrakey et al. (2016) also confirm this evidence. As frequently observed in the Aegean, European Pond Turtles were only found sporadically among Mauremys rivulata. Suitable habitats are present on Gökçeada, although only small Emys populations can be expected, based on the observations.

Figure 2. 

First record of Emys orbicularis on Gökçeada (Imbros) (May 1998) (Photo: M.F. Broggi).

Ithaca? (118 km 2)

Keymar (1986) refers to Cyren (1935) in his herpetological survey of the Ionian Islands. Cyren sighted water turtles in a well on Ithaca but was unable to identify the species. Keymar said this was all the more remarkable because Ithaca had no permanent open water. Cisterns are probably the last refugial habitats of amphibians and hydrophilic reptiles on the island. Broggi (2009) can confirm that there are no suitable habitats for aquatic turtles on Ithaca today. If Cyren’s (1935) observation is correct, M. rivulata, which has fewer habitat requirements than Emys, would probably be more likely. Strachinis and Artavanis (2017) found a new record of Bufo bufo, but equally no terrapins.

Kefalonia (773 km 2)

Werner (1894) mentions Emys for Kefalonia, but little is known about its occurrence on the island since then. Wilson (2006a) does not mention E. orbicularis at all. One occurrence known to me is in the Livadi marshes, where I was able to observe about a dozen Emys, some of them mating, during a visit to the island on 16.4.1992. The observation was repeated in April 2017. An observation was also made in a stream near the artificial Karovomilos Lake at Sami. The Livadi marshes are described in Archipelagos (2016) in a natural history article titled “Wetlands in Kefalonia”. On the webpage of the Kefalonia-Ithaca Geopark, Emys is described as “rarely seen in Kefalonia” (kefaloniapark.gr/en/node/293, later unavailable). In any case, it seems that the status of Emys on Kefalonia is endangered.

Kos (287 km 2)

The first recorder of the species for Kos is probably Fritz (1989) with a collected specimen between Kos Town and Psalidi. Kos is otherwise not mentioned for Emys in the herpetological literature (see e.g. Cattaneo 2005). In Cattaneo et al. (2020), a paper on the herpetofauna of the Dodecanese, a photo with Emys on Kos is included without further comment. Further data on finds, in taxonomic contributions by Fritz (1989) and Fritz et al. (1998), prove that the species occurs on Kos, while Bader et al. (2009) point out in their contribution on Rhodes, that on 13.4.1984 a specimen was collected between Kos Town and Psalidi (Naturhist. Museum Wien, NHMW 28291). There is also photographic evidence of Emys on Kos on the internet, for example in a field report from 8.-22.6.2006 by Wilson (2006b), who saw two Emys. Troidl (2022) presented a photo of E. orbicularis from Kos in iNaturalist. These are single data, indicating sparse populations.

Lefkas (325 km 2)

De Betta (1868) is named as the first describer by Werner (1894). Another early mention of the species is by Lehrs (1912), where he refers to several occurrences on the island. During my visit to Lefkas I saw three specimens, on 19.5.1985 in Nidri Bay, and on 20.5.1985 and 23.5.1985 in Vasili Bay. For further Emys data, see Sindaco and Rossi (2020). They found 15 specimens along Lake Maranthodi and two in a small channel near Vasiliki. The species is, therefore, present on Lefkas but probably only in small populations.

Lesbos (1,633 km 2)

I succeeded in making the first record for the island in April 1978, when I found a dead E. orbicularis on the country road at the northern end of Geras Bay (Broggi 1978). In the following days, every fifth turtle observed turned out to be Emys. More juveniles were found in a swamp south of the main town of Mytilene. Buttle (1995) did not succeed in confirming Emys, nor did Kasapidis et al. (1996). Only Perez Mellado et al. (1999) confirm this species for Lesbos with an observation of a specimen at Kopster-Myrtiotissas-Filia. Hofstra (2003) found an Emys with a carapace length of 13 cm in a polluted river near Kalloni Lake. He describes it as extremely shy, much shyer than Mauremys. In the wetlands of Kalloni Bay, the two species share the habitat. Some nature photographers have posted examples on their websites, for instance of some Emys sites, on iNaturalist (2022). Christopoulos and Zevgotis (2022) report from a 12-year study. They surveyed 119 wetlands on the island. They found them within stable populations of Emys and Mauremys. They present a distribution map with six Emys sites, compared to 83 for Mauremys. All these Emys sites were found in Kalloni Bay. The populations do not seem large but are stable according to Christopoulos and Zevgotis (2022). These authors also found three sites where Red-eared Slider Turtles (T. scripta) co-occurred with the native terrapins.

Limnos (476 km 2)

Werner (1938) does not mention Emys on Limnos. The first record was made by Schneider (1986), who found a site with two specimens behind the beach of Evgatis. Strachinis and Roussos (2016) studied the herpetofauna of the island for many years, and Strachinis found a dead specimen near Plaka on 30.7.2007, which had been killed by heavy machinery during reed harvesting. This was followed in April 2015 by his further observation of three specimens in a narrow ditch near the airfield. The authors describe E. orbicularis as threatened with extinction and refer in particular to attempts to drain back-dammed water towards the sea near Aliki. I was able to detect 11 Emys sites on the island, each with low numbers, during intensive surveys (Broggi 2017). Emys and Mauremys shared the habitat, with Mauremys being more common (Fig. 4). The assessment of the threat to the species remains valid despite these new findings.

Mykonos? (105 km 2)

Bringsøe (1985) writes that a Swedish tourist brought him a live European Pond Turtle on Mykonos. This was the first, and so far the only, find in the Cyclades. We know about the endangered status of Mauremys rivulata on the island (Broggi 2012; Broggi in press), and E. orbicularis has not been seen again since this single record. It is difficult to assess this 1985 find. Is it a release, is it a relict? Fritz (1992) writes about Tinos, “due to the recent finding of an Emys orbicularis on the neighbouring island (meaning Mykonos), however, the old record for Tinos deserves re-examination.”. The wetland situation on Mykonos has deteriorated dramatically in the meantime, whereas a suitable habitat would be available on Tinos. From today’s point of view, without further evidence, we must consider the 1985 finding as an introduction, as is now often the case for land tortoises.

Rhodes? (1,401 km 2)

Surprisingly, there is still no confirmed evidence for Rhodes. Helmdag (1993) visited the island and states: “It is possible that Emys orbicularis, the European Pond Turtle, also lives there. In any case, it seemed to me that an animal I saw belonged to this species but could only be seen once for a few seconds while taking a breath.” Bader et al. (2009) cannot confirm the species in their herpetological article on Rhodes. Although several animal photographers have visited the island in recent years, there has been no confirmation from this side either. Thus, the species` presence on the island remains unconfirmed.

Samos (477 km 2)

Calabresi (1923) and Ioannides et al. (1994) do not mention Emys for Samos in their herpetological contributions. In 1975, I also failed to find any. In a popular article on the herpetofauna of some Greek islands, Buttle (1995) mentions E. orbicularis in a list for Samos, without commenting on this or identifying it as a first record. Meyer and Fritz (1996) succeeded in establishing a reliable record of Emys on Samos on 12.4.1996. A specimen was photographed on the reedy shore of an irrigation pond near the mouth of the Tourkomyla River between the villages of Mesokambos and Mykalis in Eastern Samos. The site was about 200 metres from the seashore. Clark (2000) also mentions one observation of Emys. Speybroeck et al. (2014), in turn, report seven observations in four grids on the south-east coast. They describe Emys as “extremely rare on Samos” and thus threatened with extinction.

Samothrace (178 km 2)

Neither Werner (1938), nor Wettstein (1953) mentions the species for Samothrace, nor later do Clark (1991), Buttle (1995), Cattaneo (2001) and Ochsenhofer (2012). The first record of the species was made on the north coast, east of the Fonias stream, on 26.5.1987, when two Emys orbicularis were found in a group of Mauremys (Broggi 1988, 1994). Again, on 3.6.1987, I found Emys among Mauremys in a residual pond on the same road. The island of Samothrace is rich in water, and there are several watercourses with syphons, as well as standing water on the island (Fig. 3). The numbers of Emys are clearly low if so many herpetologists have overlooked the species, and it has not been confirmed since. On the other hand, the existence of Emys has been cited several times since then, for example in the nomination application for a UNESCO biosphere reserve in September 2013.

Figure 3. 

Estuary of the Fonias-Brook on Samothrace with first record of Emys orbicularis in May 1988 (Photo: M.F. Broggi).

Figure 4. 

Shared habitat of Emys orbicularis and Mauremys rivulata on Lemnos (22.04.2016) (Photo: M.F. Broggi).

Thassos (380 km 2)

Emys was also discovered late on Thassos. During my visit to the island in 1996 I did not see any E. orbicularis individuals. Clark (1999) also does not refer to Emys, though Fritz (2001) collected a specimen. In Fowles (2012) we read: “Emys was related as recorded from the island by Yann Horstink in July 2007 near Prinos. A single individual along with circa 20 Mauremys (was seen) in a small area of open water in a reed-filled ditch, and Lance Chilton photographed two Emys in May 2012.” Berthomieu and Vermeer (2021) mention the presence of E. orbicularis on Thassos but without citing a source. So far, these are the only references to an occurrence on the island. Information on population sizes is also missing.

Tinos? (194.5 km 2)

Werner (1938) refers to the Morée expedition in 1832 for Tinos and adds a question mark to the statement. Beutler and Frör (1980) write: “St. Hilaire (after Bedriaga 1882) lists the European Pond Turtle, Emys orbicularis, for the River Eurotes on Tinos. However, a watercourse of that name does not exist on the island; the record probably refers to the Evrotes in Laconia, where the species was found by Cyren (1941).”Fritz (1992) notes the following on the history of Tinos: “1833 Emys antiquorum Valenciennes in Bory de Saint-Vincent (Eurotes estuary Peloponnese and Tinos) “. The river is recorded here for the Peloponnese, and Tinos is given independently. Fritz (1992) considers an earlier occurrence on Tinos (and also Mykonos) as possible. Regarding suitable habitats, the lagoons of Kolimpithra and Panormos on Tinos would be quite possible for E. orbicularis, according to my own visit in 2018, but did not find it there (Broggi 2019). Likewise, for both Andros and Mykonos, a confirmation is missing.

Zakynthos (406 km 2)

Werner (1938) first mentions E. orbicularis for the island with reference to W. Kühnelt without citing the source. Keymar (1988) mentioned Emys for Lake Keri, where he saw some juveniles. Podlouky and Fritz (1994) observed two specimens at Lake Keri and believed the site was threatened by desiccation. Extinction is feared. Wilson (2006a) mentions a marsh and watercourse at Limni Keri in the south-west of the island, where he observed six individuals and also noted drainage in the area. Wilson (2009) wrote from two excursions in May 2005 and June 2006 that there was only one occurrence on Zakynthos, at Lake Keri. He observed around 20 animals there in 2005 and 30 in 2006. Urosevic (2014) recorded an adult Trachemys scripta scripta in a canal near Lake Keri and later saw a juvenile T. s. elegans there. The other turtles observed there have been Emys orbicularis in larger numbers and some Mauremys rivulata (Urosevic 2014). Pafilis et al. (2015) points to a monitoring program as a case study for Zakynthos that also includes E. orbicularis. These references are all clearly about the same endangered site on Zakynthos, and thus this species must be assessed as threatened with extinction from the island.

Discussion

Emys orbicularis lives mainly in stagnant waters along the Greek mainland and on the larger Ionian Islands except Ithaca. It is absent from Kythera, Crete and the Cyclades. Its occurrences in the Ionian area and in the Aegean are restricted to the larger islands close to the mainland that have wetlands in their coastal areas. Viable populations exist on Lesbos and Corfu, but on other islands only small populations were found. The situation seems to be particularly critical on Kefalonia, Zakynthos, Thassos and Samos.

While the sympatric species M. rivulata occurs on 29 Greek and two Turkish islands (Broggi in press), E. orbicularis has so far been found on only 11 Greek islands and one Turkish. It has rather more specific habitat requirements than Mauremys (Fritz 2001). Occurrences on Rhodes and Chios have not yet been clarified, while for four other islands early reports have never been confirmed and are therefore questionable. Samothrace, with a land area of 178 km2, is the smallest island with Emys sightings. It is obvious that only the larger islands allow large hydrological catchment areas, which can then form corresponding watercourses with estuaries.

Threats and protection

Most of the Greek islands have an arid climate and, therefore, have few wetlands due to a lack of annual precipitation (WWF-Greece 2014). According to my observations the habitats of swamp turtles in the estuaries of watercourses are often located in sandy areas and are characterized by the formation of beach walls. Sea currents can close the estuary to flowing waters, with falling water pressure then causing backwater in the form of lagoons or other smaller areas of standing water. These habitats are naturally rare in the Greek island world and tend to be small. Human influence is all the more detrimental to these hydrophilic species. A gene exchange between populations is hardly possible via land routes but only via drifting into the open sea after heavy rainfall. It is known that Emys from the Neretwa estuary in Croatia have drifted to the island of Korcula, 5km away (Jelič et al. 2012). However, the surviving animals did not find suitable habitats there. This observation supports the inter-island drift theory for the distribution of the species during the last millennia (Lymberakis and Poulakakis 2010). It is obvious that Mauremys is better adapted to this as it is more salt-resistant than Emys.

In its preferred habitat in the backwaters of sandy beaches, numerous conflicts of use arise. Tourism claims these sandy beaches and impairs or destroys habitats with its infrastructure. This affects not only the aquatic habitats but also the nesting sites needed. Intensified agriculture is also exploiting flat areas in the estuaries of watercourses. Agriculture is also involved in water loss by diverting water for field irrigation over many kilometers and thus drying out suitable habitats. It also extracts groundwater by pumping, causing watercourses to dry up more quickly. I have the impression that Emys proves to be a more sensitive species to pollution than Mauremys, which can still thrive in heavily eutrophic waters (Wischuf and Busack 2001). Similarly, refugial habitats in streams are used by Mauremys, which has not been observed for Emys, at least on the islands. All Emys occurrences on islands are in low-lying areas, on islands they hardly penetrate the streams at higher elevations. A new threat is the introduction of invasive turtles. Cady and Joly (2004) find weight loss and high mortality of E. orbicularis in mixed groups, and their study calls for a halt to slider turtle introduction in all European wetlands. Likewise, ongoing climate change with drying tendencies may be another threat.

Emys orbicularis is a species in Greece protected by national legislation (Presidential Decree 67/1981). It is also protected and listed in Annex II of the EU Habitats Directive, as well as by the Bern Convention. It is believed that many wetlands on the islands have been destroyed in the past century (WWF-Greece 2014). WWF-Greece mapped 824 wetland structures on 76 islands in 2004–2013. Of these, 100 are in the Ionian Islands, 526 in the Aegean and 192 in Crete. The data is available at oikoskopio.gr/ygrotopio (WWF-Greece 2014). In a presidential Act in 2012, 350 properties on 58 islands were placed under protection. According to Paragamian et al. (2014), this is said to have been extended from 350 to 562, which corresponds to around 70% of all those in the inventory. Enforcement of protection will now have to be monitored; some of our own observations suggest these decrees are being disregarded.

The present study is a second report on the occurrence and status of E. orbicularis on the Greek islands. It is based on literature studies, although there are certainly gaps in our knowledge. In addition, the author and his colleagues were able to visit about 60 Greek islands, with local inspections, to get a picture of the prevailing habitat conditions. The assessment of threats to Emys orbicularis on the individual islands is not based on monitoring, as such data are lacking. It is my subjective expert assessment. This is mostly based on a systematic search of suitable habitats on the islands. However, such findings may date back many years and thus be outdated. The occurrences of Emys orbicularis on the islands are usually very isolated, their populations small and therefore vulnerable. Accordingly, the occurrences of Emys orbicularis are endangered and must be ensured through conservation measures. The report explicitly refers to open questions that need to be closed by further field herpetological work. The most obvious is the clarification of the occurrence of E. orbicularis on Chios and Rhodes.

Acknowledgments

I would like to thank my faithful companions Dr. Peter Goop, Vaduz, and Mag. Günter Stadler, Frastanz (Vorarlberg) for their help on the excursions. We remember our deceased colleagues Edith Waldburger, Buchs SG, Wilfried Kaufmann, Balzers FL, and Dr. Christian Burri, Untervaz GR. A thank you also to the three evaluators and the editors for their valuable advice.

References

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