Taxonomic Notes
This taxon was previously treated as a subspecies of Mauremys caspica, but later considered a full species (see discussion by Fritz 2001).
Justification
European regional assessment: Least Concern (LC)
EU 27 regional assessment: Least Concern (LC)
Within the European region, this species ranges from the central Balkan Peninsula, through most of Greece, to the Greek Aegean Islands and European Türkiye. It is assessed regionally for Europe and for the EU27 Member States as Least Concern in view of its wide distribution, tolerance of a degree of habitat modification, presumed large population, and because it is unlikely to be declining fast enough to qualify for listing in a threatened category. No adjustment to the Category is applied according to the IUCN regional and national Guidelines (IUCN 2012).
Declines have been reported for a number of populations in some European countries. The reasons for these declines are given as urbanisation, habitat loss due to water availability and use, presence of species nesting sites on agricultural land - affected either by intensive production and toxins or loss of open water for agricultural use. It is likely that in the next few years that the species could qualify as threatened under A2c because of these widespread but local declines. For instance, it has already been assessed as EN in Croatia and North Macedonia, and local extinctions have been documented in Greece. As it inhabits few countries in Europe, mostly developing ones, it is clear that not enough data has been collected on this species compared to the European Pond Turtle. It inhabits Mediterranean freshwater habitats that are continuously declining and will continue to do so with climate change – more so than the ones inhabited by Emys, and monitoring of population trends and habitat trends is required for this species.
Geographic Range Information
Within the European region, this species ranges from southern coastal Croatia, Montenegro and Albania, southeastern North Macedonia, southeastern and southwestern Bulgaria (Kornilev et al. 2017), through most of Greece (including many Aegean and Ionian islands), to the Marmara Sea region of European Türkiye (Mantziou and Rifai 2014). Among the Mediterranean islands it occurs on are Cyprus, Crete, Rhodes, and Corfu (Iverson 1992, Gasperetti et al. 1993, Wischuf and Busack 2001, Mantziou and Rifai 2014).
In detail for Croatia, four extant subpopulations are known:
1. Majkovi and Prljevići: stable since 2006 at about 150 (known) individuals – no future decline suspected.
2. Konavle: subpopulation discovered in 2008 and stable since then at about 350 animals, final calculations for 2019 required) – no future decline suspected.
3. Ston: A decline was recorded in 2004, suspected since the 1970s (suspected based on archaic video footage and extensive field sampling in 2004-2006 and 2018-2019, numbers caught too low for M-RC). Suspected stable in 2018 at the same low number (six records confirmed after extensive sampling, numbers caught too low for M-RC). The population size projection of growth for the Ston subpopulation as a result of planned conservation breeding +40 animals in 5 years.
4. Ombla River in Rijeka dubrovačka – historical records confirmed in 2018 (two records), more research is required for correct conclusions. A further subpopulation in the Neretva delta, southern Croatia was mentioned in the national Red Book in 2015; there are no previous literature records of this subpopulation and no records found during fieldtrips 2014-2019. A further old record from southern Croatia (Baćinska Lake) exists of one individual, however, there are no subsequent literature records, and no records during field trips 2018-2019.
In Croatia, a population due to habitat loss is inferred as a result of urbanisation over the previous 60 years. For example, at Rijeka Dubrovačka, the delta of the River Ombla, currently, only two individuals were recorded there in the last five years. Changes in agriculture practices have also impacted subpopulations: surface waters such as ponds and agromeliorative canals have been neglected in the Ston area, leading to population declines since the 1970s; as recently as 2019, only five individuals were recorded after extensive searching during two consecutive seasons. In addition, a decline is inferred due to the use of unselective fish nets (fyke nets, crab traps and mostly illegal eel traps) in the Ston area and possibly also the Neretva Delta – Neretva is designated as a Natura 2000 site, with no recent findings and findings in the past are questionable).
In Montenegro, the species is present in a narrow coastal area in smaller streams, rivers, and swamps, ponds, canals, marshes from Herceg Novi to Ulcinj (Gvozdenović and Iković 2016, Mićanović et al. 2022). A significant anthropogenic impact is inferred because of tourism development, urbanisation, and the discharge of unprocessed waste (Mićanović et al. 2022). At Skadar Lake, subpopulations are not registered (A. Vujović pers. comm. April 2023). In the Sutorina area of Montenegro, close to the Konavle subpopulation in Croatia, low genetic diversity and high inbreeding have been recorded (conference presentation in February 2023).
The European and EU extent of occurrence and area of occupancy are both large.
The species' distribution extends eastwards out of the European region through the Mediterranean regions and river basins of Türkiye to western Syria, Lebanon, northwestern Jordan and northern, Palestine and central Israel. It is found from sea level up to 900 m asl. The Tigris-Euphrates-basin waterbodies in Türkiye are inhabited by M. caspica.
Population Information
The main demographic characteristic of this turtle species is that it may reach very high densities locally. Indeed, it is possibly the freshwater turtle occurring at the highest densities reported, with 19-217 animals per hectare in unpolluted habitats, and over 500 to 2,000+ animals per hectare in an eutrophic wetland (Wischuf and Busack 2001:102). Obviously, these estimates depend very much on the method used for gathering the data and the scale of the study, so it is possible that the actual figures are not as high as suggested in the above-mentioned studies. For example, density is generally high in August on the remains of temporary waterflows that the species uses, not over the whole habitat area. The marginal Bulgarian subpopulation, small at about 1,000 animals, appears to have remained stable (Beshkov 1987, in Wischuf and Busack 2001:102).
Marginal subpopulations at the edge of the species range and those on small islands are considered as the ones most at risk, but this is somehow expected given that peripheral subpopulations are usually rarer in all reptile populations studied to date (Vamberger et al. 2014). In North Macedonia, there have been significant declines as a result of habitat loss and habitat alteration (L. Tomović pers. comm. January 2023), however, the overall population trend is considered stable. Among the areas of demonstrated decline, were the Ombla River and the Ston area. In the Neretva delta, the species is not present. In Montenegro according to preliminary data collected for five years, the population size of Mauremys rivulata in the Igalo (Herceg Novi), Tivat and Buljarica (Budva) is over 300 individuals per site, and in the Jaz (Budva) is over 350 individuals (Mićanović et al. 2022). Habitats in Montenegro have been shrinking for the last 50 years, and their area has been rapidly decreasing over the last 20 years due to unsustainable tourism, sewage, and concreting of watercourses and some populations have disappeared because the concreting of the stream bed (Mićanović et al. 2022). It is difficult to make specific conclusions about changes in distribution area in Croatia. The population from Konavle field (that was only discovered around 20 years ago) is the most numerous and spatially widespread in Croatia. In Baćinska Lake, literature data report only one individual (that was seen through binoculars) from the end of the 1980's, and this sighting is questionable, and this locality record was not confirmed later despite detailed recent surveys. Apparently, the area of favourable habitat in Ston field has decreased from 100 ha to today's less than 10 ha. Also, habitats on the Ombla River have decreased - from the area of the entire river (30 m), wetland area with a pond on the islet of Blato. The surrounding agricultural canals and canals of former mills to one an irrigation channel and a small puddle next to it (Štih and Šalamon 2019). Regarding the number of Mauremys in Croatia, it can be concluded that the number has decreased over the years, taking into account the disappearance of the subpopulation from the Baćina lakes, for which there are no data on the initial number or the time of the disappearance of the subpopulation (but we can not tell for sure if it even was initially there). The number has also been significantly reduced both in the area of Ombla River and in the area of Ston field. The subpopulation in Majkovi is considered stable with around 130 estimated individuals, while the Konavle field subpopulation was initially estimated at 350 individuals, but new information about the distribution in the field and surrounding area requires a new assessment (Šalamon and Štih 2019).
Despite these local declines, the overall population trend is considered stable.
Habitat and Ecology Information
This species is certainly a habitat generalist, utilising a range of natural and anthropogenic wetland habitats (Mantziou and Rifai 2014). It inhabits slow-moving and standing freshwater bodies, permanent and temporary, usually with muddy bottom and dense aquatic vegetation. The species has also been recorded from swamps and marshes and from fast flowing rivers. It can tolerate saline and polluted conditions and can take advantage of certain human habitat alterations (irrigation canals, ditches, water storage ponds, etc.; Wischuf and Busack 2001:99,102). Females may produce two clutches of four to nine (exceptionally 12) eggs per year. The age at maturity has apparently not been recorded. The diet of this species is quite opportunistic, and it includes many aquatic invertebrates, tadpoles, small fishes and a considerable amount of plants and algae. Adults are generally less carnivorous than juveniles and subadults.
Threats Information
The main threat is certainly represented by habitat loss, and subpopulations in parts of its European range have been noted to be impacted by agricultural pesticides, agricultural development, and habitat alteration and loss relating to tourism development (Atatur 1995; L. Tomović pers. comm. January 2023). Drainage of wetlands have a locally significant impact on subpopulations but is unlikely to endanger the species as a whole. In Greece, there have been a number of extinctions and declines of island subpopulations, often through the destruction of freshwater habitats (e.g., Paros Island). It is additionally threatened by the overuse and pollution of freshwater habitats, especially temporary freshwaters (e.g., Cyprus). There are likely to be an increasing number of threats to this species with increasing water demands in the region. Repurposing or purpose loss of open water for agriculture, Illegal fishing of eels, and other (Stonefield in the Neretva delta).
Competition with the introduced
Trachemys scripta has been suggested as a possible threat in parts of its range (e.g., Crete), but there is no scientific evidence that it may be the case; Mantziou and Rifai (2014) suggest that competition for food and other resources might be the main threat.
In Montenegro there are registered cases of illegal collection and sales of this species. In this region, there is a large anthropogenic impact because of urbanization, intense pressure from regulation of the river bed, exploitation of gravel and the increased amount of waste waters which leads to the accelerated growth and eutrophication of wetlands and tourism development (Mićanović et al. 2022, Gvozdenović and Iković 2016, Vujović pers. comm. April 2023).
Use and Trade Information
No use by local people has been documented in the available literature in Europe. It occasionally appears in the pet trade, and it is considered to be over-collected for the pet trade in Türkiye; the species is easily bred in captivity and any trade is almost certainly from captive-bred sources (P.P. van Dijk pers. comm. January 2023). Several confiscations were done at the Croatian borders in the last 15 years, with also one attempt of illegal breeding. Touristic interpretative centres in Natura2000 areas in Croatia are focused on the species – potential economic value.
