Introduction
The availability of reliable maps that depict the historical and current distribution of reptile species is important for conservation research (Sillero et al., Reference Sillero, Campos, Bonardi, Corti, Creemers and Crochet2014). Reptiles are a good model group for mapping studies because they are dependent on specific habitat types, have narrow ranges and are sensitivite to anthropogenic factors (Sinervo et al., Reference Sinervo, Méndez-de-la-Cruz, Miles, Heulin, Bastiaans and Villagrán-Santa Cruz2010; Böhm et al., Reference Böhm, Collen, Baillie, Bowles, Chanson and Cox2013). Many groups of reptiles are affected both directly and indirectly by anthropogenic impacts, particularly those that result in habitat loss and transformation (Wake & Vredenburg, Reference Wake and Vredenburg2008; Keinath et al., Reference Keinath, Doak, Hodges, Prugh, Fagan and Şekercioğlu2017).
Ukraine has relatively low levels of species richness compared to other European countries (Sillero et al., Reference Sillero, Campos, Bonardi, Corti, Creemers and Crochet2014), especially in the steppe zone (Tarashchuk, Reference Tarashchuk, Bilanovskyi, Voinstvenskyi, Kasyanenko, Markevich and Pidoplichko1959). Odesa Oblast (i.e. province) is part of the Azov–Black Sea eco-corridor in the steppe zone, and this area is important for biodiversity conservation in Ukraine and Europe (Szczerbak, Reference Szczerbak1988; Kotenko, Reference Kotenko2006). It is of particular relevance for local herpetofauna species that are protected at the national or international level (Akimov, Reference Akimov2009; IUCN, 2023). Records of these species are limited compared to other parts of the country, and much of the data are old or ambiguous, especially for rare species (Brauner, Reference Brauner1907; Volyansky, Reference Volyansky1928; Kotenko & Tarashchuk, Reference Kotenko and Tarashchuk1982; Tarashchuk, Reference Tarashchuk1987; Szczerbak, Reference Szczerbak1988). In this area, reptiles face severe threats, including alteration and fragmentation of their native habitats, uncontrolled pressure from infrastructure projects, and pollution and climate change (Kotenko & Panchenko, Reference Kotenko and Panchenko1992). In addition, warfare is currently having negative impacts on Ukraine's ecosystems (Vasyliuk, Reference Vasyliuk2023). Fourteen native reptile species have been recorded in Odesa Oblast (Kotenko & Tarashchuk, Reference Kotenko and Tarashchuk1982; Dotsenko & Radchenko, Reference Dotsenko and Radchenko2005) but only dubious records exist for some of these (Szczerbak, Reference Szczerbak1988; Tarashchuk, Reference Tarashchuk1989; Kotenko, Reference Kotenko1999). In addition, this area is a corridor for introduced species (Duz et al., Reference Duz, Kukushkin and Nazarov2012; Matvyeyev et al., Reference Matvyeyev, Kukushkin and Sokolov2013; Krasylenko & Kukushkin, Reference Krasylenko and Kukushkin2017; Oskyrko et al., Reference Oskyrko, Laakkonen, Silva-Rocha, Jablonski, Marushchak, Uller and Carretero2020, Reference Oskyrko, Lysenko and Jablonski2022a) and these need monitoring and management. Here we report the results of a comprehensive study of reptile distribution in this oblast.
Study area
Odesa Oblast lies in south-west Ukraine, bordering the Black Sea. In the south it borders Romania and in the west Moldova (Fig. 1). The 33,314 km2 oblast comprises mostly hilly plains and flat steppes. It also includes an important historical region: Ukrainian Bessarabia. This area is bounded by two large rivers that are significant biogeographical barriers: the Dniester in the north and the Danube in the south. Odesa Oblast connects the eastern Carpathian and the European steppe areas. Most of the oblast lies in the Black Sea lowland, which gradually decreases in elevation towards the south-east (from 150–170 m to 10–20 m; Vermenich, Reference Vermenich and Smoly2010). The climate is moderately continental, with mild winters and little snow (−5.8 to −1.8 °C in January) and hot, dry summers (21.0–22.9 °C in July). Total annual precipitation is 380–500 mm (Vishnevsky, Reference Vishnevsky2009). There are 225 rivers in the oblast, of which the Danube and the Dniester are the most important. Odesa Oblast has 123 protected areas with a total area of 1,599 km2 (Fig. 1). The largest are the Danube Biosphere Reserve, Tuzly Lagoons National Nature Park and Lower Dniester National Nature Park.
Odesa Oblast, Ukraine, indicating geographical areas and places mentioned in the text.
Methods
We compiled location data and created distribution maps for species based on four sources: our own data, museum collections (the National Museum of Natural History at the National Academy of Sciences of Ukraine in Kyiv), published data (Supplementary Material 1) and public databases (UkrBIN, Reference kr2017; GBIF, 2023). We compiled records for all of Odesa Oblast. From the public databases we only used records with accompanying photographs, to confirm species identification. We based species identification on Arnold & Ovenden (Reference Arnold and Ovenden2002) and followed the taxonomy of Speybroeck et al. (Reference Speybroeck, Beukema, Dufresnes, Fritz, Jablonski and Lymberakis2020). We did not consider subspecies, and therefore represent Vipera berus nikolskii as Vipera ursinii (Mizsei et al., Reference Mizsei, Zinenko, Sillero, Ferri, Roussos and Szabolcs2018; Speybroeck et al., Reference Speybroeck, Beukema, Dufresnes, Fritz, Jablonski and Lymberakis2020).
We conducted herpetological field surveys across the whole area during April–September 2012–2022 (each survey lasted 3–7 days and was conducted by 3–5 people). We surveyed throughout the day (8–10 h of fieldwork) whenever weather conditions were suitable. These surveys were either transects of varying lengths or targeted species searches, covering all habitats. We employed the line transect method, recording and identifying all reptiles found c. 5 m either side (Lovich et al., Reference Lovich, Hayes, Mushinsky, Rodda, McDiarmid, Foster and Guyerm2012; McDiarmid et al., Reference McDiarmid, Foster, Guyer, Gibbons and Chernoff2012). We collected data using dip-netting, netting, trawling of water bodies, stone-turning and other refugia searches as well as visual searches. We documented our observations with digital photographs of individuals, when possible, and of habitats. We released any captured animals at the capture site. In addition, we examined animals killed by people or vehicular traffic. We recorded geographical coordinates and altitudes for all observations using a GPS.
We collected data from the National Museum of Natural History at the National Academy of Sciences of Ukraine in Kyiv in 2021. We did not include published data with unspecified coordinates that could not be georeferenced to a specific locality. We manually georeferenced occurrences without geographical coordinates to the finest scale possible using the information provided by the source and Google Earth (Reference Google Earth2022). The accuracy of published localities was within 5 km, except for the data from Sillero et al. (Reference Sillero, Campos, Bonardi, Corti, Creemers and Crochet2014), which were within 10–50 km. We recorded the geographical coordinates and altitudes of all visited localities as well as other relevant faunistic data. We created maps using QGIS 3.30 (QGIS, 2022). The distribution data of individual species are presented in maps with a grid of 462 10 × 10 km cells. We categorized presence records as: new occupied cells based on our own records; unverified data from the literature, public databases and museum collections; previous records in cells confirmed by our new records; and historical records that have not been reconfirmed in the last 25 years. We calculated species richness of native reptiles per 10 × 10 km grid cell in R 4.2.2 (R Core Team, Reference Core Team2022) using the vegan package (Oksanen et al., Reference Oksanen, Blanchet, Friendly, Kindt, Legendre and McGlinn2019). We obtained shapefiles for protected areas in Ukraine from UNEP-WCMC & IUCN (Reference &2023).
Results
We compiled 662 records of all 14 known native reptile species (200 from our survey data, 27 from museum collections, 362 from published literature and 73 from public databases; Table 1, Fig. 2). This represents 66.6% of the total number of known species in Ukraine. These records include one species of Anguidae (Anguis colchica), six of Colubridae (Coronella austriaca, Dolichophis caspius, Elaphe sauromates, Natrix natrix, Natrix tessellata, Zamenis longissimus), one of Emydidae (Emys orbicularis), four of Lacertidae (Eremias arguta, Lacerta agilis, Lacerta viridis, Podarcis tauricus) and two of Viperidae (Vipera berus, Vipera ursinii). We did not record any new species. In our field surveys we were unable to confirm the occurrence of five of the 14 known species (A. colchica, C. austriaca, Z. longissimus, V. berus, V. ursinii).
The 14 native reptile species recorded in Odesa Oblast, Ukraine (Fig. 1), with number of records (% of total), number of occupied 10 × 10 km grid cells (% of total), number of records in protected areas (% of total), inclusion in the Red Book of Ukraine (Akimov, Reference Akimov2009), IUCN Red List status and Plate reference.
1 LC, Least Concern; NT, Near Threatened; VU, Vulnerable.
(a) Number of reptile species and (b) number of records in 10 × 10 km grid cells across Odesa Oblast (Fig. 1).
Of the 462 10 × 10 km grid cells, we recorded reptiles in 349 (75.2%), of which there were 64 new grid cell records for eight native species. We found 261 records in protected areas (40.4% of all records; Table 1). Emys orbicularis is categorized as Near Threatened on the IUCN Red List (Tortoise & Freshwater Turtle Specialist Group, 1996) and V. ursinii as Vulnerable (Joger et al., Reference Joger, Isailovic, Vogrin, Corti, Sterijovski and Westerström2009). Seven species (L. viridis, C. austriaca, D. caspius, E. sauromates, Z. longissimus, V. berus, V. ursinii) are listed in the Red Book of Ukraine (Akimov, Reference Akimov2009). Emys orbicularis had the most records in protected areas (60.6%). For three species found in protected areas (A. сolchica, Z. longissimus, V. berus) there was only one record of each. Most data are concentrated in Ukrainian Bessarabia and near the city of Odesa, which served as the working base for most of the field trips. In addition, the number of species and records per grid cell were highest in these areas (Fig. 2). The maximum number of records in a single cell was 33 (for six species) between the villages of Mykolaivka and Kurortne in southern Odesa Oblast. The highest number of species (eight) was near Odesa and lakes Yalpuh and Kuhurlui (near the border with Romania).
We recorded eight species in grid cells in which they had not been reported previously (Fig. 3). Our new records confirm the occurrence of E. arguta in Odesa Oblast. In Ukraine, this species is limited to the steppe and forest–steppe zone, in habitats with sandy and sandy–shelly soils and sparse psammophilous steppe and halophile herbaceous vegetation (Szczerbak, Reference Szczerbak1993; Plates 1c & 2a). With respect to both the per cent of the total of 654 records and of the 462 grid cells occupied, D. caspius, L. agilis and L. viridis were the commonest and most widely distributed species, respectively (Fig. 3, Table 1). Dolichophis caspius is widespread but probably occurs at a low density and hence is rarely observed; although there are records of this species in 59 grid cells, we confirmed its presence in only eight grid cells. We recorded the widespread and common L. viridis and L. agilis in 54 and 58 grid cells, respectively (Fig. 3).
The distribution of the 14 known native species of reptiles in Odesa Oblast, presented in 10 × 10 km grid cells. (Readers of the printed journal are referred to the online article for a colour version of this figure.)
Representative photographs of reptile species in Odesa Oblast, Ukraine (Fig. 1). (a) Natrix natrix, Lake Yalpuh; (b) Emys orbicularis, Lower Dniester National Nature Park; (c) Eremias arguta, Budak spit; (d) Lacerta agilis, juvenile, Myrne; (e) Lacerta viridis, Reni; (f) Podarcis tauricus, Lake Yalpuh. Photos: O. Oskyrko (a,b,d,f), R. Lysenko (c,e).
Representative habitats of reptiles in Odesa Oblast. (a) Habitat of Eremias arguta, Budak spit; (b,c) habitat of Lacerta agilis, Natrix natrix and Natrix tessellata, Tuzly Lagoons National Nature Park; (d) habitat of Lacerta agilis near the village of Kurortne. Photos: R. Lysenko (a,d), O. Oskyrko (b,c).
The European pond turtle E. orbicularis was found along estuaries, lakes and large rivers such as the Danube and Dniester. Most of the populations of the lizards were syntopic. We did not find A. colchica in the published locality or in other parts of the oblast. We found a new record of E. arguta near the village of Pidhirne (46.261°N, 30.029°E). Some of our records for the other species of lizards are new localities but in areas where these lizards were previously known. We frequently recorded N. natrix and N. tessellata near large estuaries, lakes and large rivers, but these species have a scattered distribution. We found two new records of E. sauromates, near the village of Zelena Balka (45.927°N, 29.585°E) and Burnas estuary (45.858°N, 30.137°E). Dolichophis caspius was the most common snake, with a high number of observations per grid cell, and our findings confirm previous research on the species’ range in Odesa Oblast (Tarashchuk, Reference Tarashchuk2007; Sillero et al., Reference Sillero, Campos, Bonardi, Corti, Creemers and Crochet2014; Nekrasova et al., Reference Nekrasova, Dyadchko, Grandova, Kuzemko, Sadogurskaya, Goldin, Kavurka, Kutsokon and Nekrasova2020).
We found 16 records of four introduced species of reptiles (seven from our survey data, eight from the published literature and one from a public database): Trachemys scripta (Emydidae), Tenuidactylus bogdanovi (Gekkonidae), Podarcis muralis (Lacertidae) and Pseudopus apodus (Anguidae) (Fig. 4). We found five new records for T. scripta, in artificial reservoirs in Odesa. We confirmed the published records for T. bogdanovi and P. muralis and did not observe any expansion of their range. Information about P. apodus has been published previously (Oskyrko et al., Reference Oskyrko, Lysenko and Jablonski2022a,Reference Oskyrko, Sreelatha, Silva-Rocha, Sos, Vlad and Cogălniceanub), and we did not find any new records of this species.
The distribution of the four known introduced species of reptiles in Odesa Oblast, presented in 10 × 10 km grid cells. See Fig. 3 for key. (Readers of the printed journal are referred to the online article for a colour version of this figure.)
Discussion
Reptile distribution
There is less species distribution data available for Ukraine in general compared to other European countries (Sillero et al., Reference Sillero, Campos, Bonardi, Corti, Creemers and Crochet2014), which is typical of countries of the former USSR (Zizka et al., Reference Zizka, Rydén, Edler, Klein, Aronsson and Perrigo2020), and much of the published research on the reptiles of Odesa Oblast dates from the Soviet era (e.g. Tarashchuk, Reference Tarashchuk, Bilanovskyi, Voinstvenskyi, Kasyanenko, Markevich and Pidoplichko1959; Bannikov et al., Reference Bannikov, Darevsky and Rustamov1971; Yablokov, Reference Yablokov1976). Some of the records from that era do not contain location information (e.g. Tarashchuk, Reference Tarashchuk, Bilanovskyi, Voinstvenskyi, Kasyanenko, Markevich and Pidoplichko1959; Kurylenko & Verves, Reference Kurylenko and Verves1999) and were therefore not included in our analysis. Our present compilation, however, is the most complete database to date of reptile occurrences in Odesa Oblast, although the distribution of five of the 14 species (A. colchica, C. austriaca, Z. longissimus, V. berus, V. ursinii) remains poorly known and we were unable to confirm their presence. Our survey efforts and those of earlier researchers were not evenly distributed across the oblast and this may partly explain why there are more records in some grid cells, especially near Odesa, for example (Figs 2 & 3).
Anguis colchica was found in the 1990s in Savran Forest (Kotenko, Reference Kotenko, Fedorenko, Rogatko, Lysenko, Kotenko and Volovnik1990) but the species has not been recorded since then (Dotsenko & Radchenko, Reference Dotsenko and Radchenko2005). The rarity of records could be a result of the low detectability and secretive habits of this species. The earliest record of C. austriaca was in 1827 in Holodna Balka (Dotsenko & Radchenko, Reference Dotsenko and Radchenko2005) but some individuals were subsequently found in Odesa Oblast (Brauner, Reference Brauner1923; Volyansky, Reference Volyansky1928; Tarashchuk, Reference Tarashchuk1987; Dotsenko & Radchenko, Reference Dotsenko and Radchenko2005). The rarity of this species in the Oblast is probably because of habitat alteration by agriculture. Zamenis longissimus was recorded in 1985 (and there was an earlier record; Nikolsky, Reference Nikolsky1916) but has not been recorded since, despite intensive searches. We believe this species could still occur in Odesa Oblast as there are suitable habitats near the Dniester River. The earliest recorded observations for V. ursinii were in the 1920s (Brauner, Reference Brauner1923; Volyansky, Reference Volyansky1928), and for V. berus in the 1990s (in Savran Forest; Kotenko, Reference Kotenko1999), but we did not record either species. However, confirmation of the distribution of V. ursinii in this area was recently published (Mizsei et al., Reference Mizsei, Zinenko, Sillero, Ferri, Roussos and Szabolcs2018). Both of these species are threatened by past and ongoing habitat loss and fragmentation. As these five species are rare, further surveys in their preferred habitats are required.
In the south, species richness was higher in the vicinity of the city of Odesa than in the northern part of the oblast. This could indicate synanthropy for some species and/or a result of the greater number of surveys in this area. Species richness was also high along the Black Sea coast (Fig. 2), perhaps as a result of the protected areas in this region (Fig. 1). Compared to the neighbouring Mykolaiv Oblast (935 records), Odesa Oblast has fewer reptile records (Oskyrko & Jablonski, Reference Oskyrko and Jablonski2021). This could be because of fewer surveys and/or fragmentation of habitats and uncontrolled pressure from infrastructure projects in Odesa Oblast (Kotenko & Panchenko, Reference Kotenko and Panchenko1992).
Odesa Oblast has the highest number of introduced species of reptiles of all Ukrainian oblasts. We confirmed the presence of all except P. apodus (Fig. 4). Pseudopus apodus is included in the Red Book of Ukraine (only for the Crimea; Akimov, Reference Akimov2009) and is categorized as Least Concern on the IUCN Red List (Aghasyan et al., Reference Aghasyan, Avci, Tuniyev, Crnobrnja-Isailovic, Lymberakis and Andrén2021). This species is distributed in the Western Palearctic from the Balkans through to Anatolia and Central Asia; in Ukraine it is native only in Crimea (Sindaco & Jeremcenko, Reference Sindaco and Jeremcenko2008; Oskyrko et al., Reference Oskyrko, Lysenko and Jablonski2022a). We did not find increased ranges for T. bogdanovi and P. muralis compared to earlier studies (Matvyeyev et al., Reference Matvyeyev, Kukushkin and Sokolov2013; Krasylenko & Kukushkin, Reference Krasylenko and Kukushkin2017; Oskyrko et al., Reference Oskyrko, Laakkonen, Silva-Rocha, Jablonski, Marushchak, Uller and Carretero2020). These species are not included in the Red Book of Ukraine and are categorized as Least Concern on the IUCN Red List (Böhme et al., Reference Böhme, Pérez-Mellado, Cheylan, Nettmann, Krecsák and Sterijovski2009; Nazarov, Reference Nazarov2017). Tenuidactylus bogdanovi is native to Uzbekistan, southern Tajikistan, Kazakhstan and parts of Turkmenistan (Nazarov, Reference Nazarov2017). These geckos in Ukraine comprise the only European population and were probably imported with cargo from Central Asia (Duz et al., Reference Duz, Kukushkin and Nazarov2012). Podarcis muralis is distributed from the Iberian Peninsula to Asia Minor, but is also native to extra-Mediterranean regions in eastern Central and Eastern Europe (Sindaco & Jeremenko, Reference Sindaco and Jeremcenko2008; Schulte et al., Reference Schulte, Veith and Hochkirch2012). These lizards were introduced into Ukraine via cargo boats on the Danube River from Romania (Oskyrko et al., Reference Oskyrko, Laakkonen, Silva-Rocha, Jablonski, Marushchak, Uller and Carretero2020). We found new records of T. scripta near the city of Odesa. Its native range is central, southern and south-eastern USA and north-eastern Mexico (Semenov, Reference Semenov2010; Rhodin et al., Reference Rhodin, Iverson, Bour, Fritz, Georges, Shaffer, Rhodin, Iverson, van Dijk, Stanford, Goode, Buhlmann and Mittermeier2021). There were numerous sightings of this species in various oblasts of Ukraine at the beginning of the 21st century (Кurtyak & Kurtyak, Reference Кurtyak and Kurtyak2013; Kukushkin et al., Reference Kukushkin, Doronin, Tuniyev, Ananjeva and Doronina2017; Nekrasova et al., Reference Nekrasova, Tytar, Pupins and Čeirāns2022) and in other European countries (Cadi & Joly, Reference Cadi and Joly2004; Pupins & Pupina, Reference Pupins and Pupina2011; Kornilev et al., Reference Kornilev, Lukanov, Pulev, Slavchev, Andonov and Vacheva2020; Rhodin et al., Reference Rhodin, Iverson, Bour, Fritz, Georges, Shaffer, Rhodin, Iverson, van Dijk, Stanford, Goode, Buhlmann and Mittermeier2021). This species requires monitoring as it can be a threat to local biodiversity (Ficetola et al., Reference Ficetola, Rödder, Padoa-Schioppa and Francis2012). The number of introduced species is increasing in Europe (Asztalos et al., Reference Asztalos, Wielstra, Struijk, Ayaz and Fritz2021; van Doorn et al., Reference van Doorn, Speybroeck, Brys, Halfmaerten, Neyrinck, Engelen and Adriaens2021; Oskyrko et al., Reference Oskyrko, Sreelatha, Silva-Rocha, Sos, Vlad and Cogălniceanu2022b), and requires monitoring in Ukraine.
Conservation
The main threats to reptiles in Europe are agriculture, residential/commercial development, competition for biological resources and habitat fragmentation (Visconti et al., Reference Visconti, Elias, Sousa, Fischer, Ali-Zade, Baldi, Rounsevell, Fischer, Torre-Marin Rando and Mader2018). The steppe biome, which has undergone significant anthropogenic transformation in south-west Ukraine (Kotenko & Panchenko, Reference Kotenko and Panchenko1992), is particularly threatened (Wesche et al., Reference Wesche, Ambarlı, Kamp, Török, Treiber and Dengler2016). Odesa Oblast contains c. 2.5 million ha of agricultural land, including 2 million ha of arable land and 80,000 ha of vineyards and orchards (Kotenko & Panchenko, Reference Kotenko and Panchenko1992). In addition, there is significant tourism related to the Black Sea and the therapeutic mud of the region and its mineral waters (Kotenko, Reference Kotenko1999). Tourism related activities can damage the natural steppe areas, which are amongst the largest in Europe (Kotenko, Reference Kotenko1999; Kotenko & Panchenko, Reference Kotenko and Panchenko1992). In addition, war has a significant destructive impact on nature (Daskin et al., Reference Daskin, Stalmans and Pringle2015; Gaynor et al., Reference Gaynor, Fiorella, Gregory, Kurz, Seto, Withey and Brashares2016; Braga-Pereira et al., Reference Braga-Pereira, Peres, Campos-Silva, Santos and Alves2020), and the current war with Russia is affecting the steppe zone of Ukraine, including in Odesa Oblast (Vasyliuk, Reference Vasyliuk2023). The most extensive of these negative consequences are fires caused by the firing of ammunition and explosions from mines, but also the explosions of other munitions and the destruction of military equipment, which together can cause long-term soil and surface water pollution.
Conservation of the remaining unique habitats of Odesa Oblast is important for its flora and fauna, including for its reptile species. In this context, distribution data is vital for informing conservation management decisions. The data we have compiled will inform investigations of population changes and modelling of the potential consequences of environmental and climate change. We recommend that future research on the reptiles of Odesa Oblast should focus on: (1) Surveys for the five previously recorded species that we were unable to confirm. (2) Further surveys in the north, which has been less surveyed than the south. (3) The expansion of existing or creation of new protected areas, as the habitats of Odesa Oblast face significant further losses and fragmentation. (4) Raising awareness of reptiles and involving local communities in their conservation, as these are essential to ensure the success of any conservation actions and to establish sustainable land use. (5) Further research in conjunction with local and governmental support for the development of species conservation programmes.
Author contributions
Study design: OO; fieldwork and data collection: all authors; data analysis: OO; writing: all authors.
Acknowledgements
We thank the administration and employees of Tuzly Lagoons National Nature Park and Danube Biosphere Reserve for supporting our research; the staff of the National Museum of Natural History at the National Academy of Sciences of Ukraine in Kyiv for help with museum collections; all the volunteers for their help with fieldwork and data collection; and the editor and reviewers for their valuable comments. This study was supported by a Rufford Small Grant ‘Setting conservation priorities for reptiles and their habitats in the Ukrainian Bessarabia’ (ID 34322-2).
Conflicts of interest
None.
Ethical standards
This research abided by the Oryx guidelines on ethical standards.
Data availability
The data that support the findings of this study are available at doi.org/10.15468/uq7qrv.
Open access
