In Water Matters we wrote some time ago about the common osprey Pandion haliaetus – a majestic raptor bird, perfectly adapted to life above water, close to extinction in Poland and saved with no small effort under the LIFE project. A reptile with this name can also be found in Poland. The osprey Natrix tesselata is still an object of debate. Its status remains unclear in our country. Scientists cannot decide whether it should be protected, as a climatic relic, or rather the other way around: humanely but decisively removed (trapped and sent back to areas where it is native) as an alien species.
Osprey snake – its own or a stranger?
One of the most important problems of biogeography is explaining the origin of sparse populations of species typical of other climate-plant zones. Some of them are fully native. They are relicts of the former climates of our lands, e.g.: populations of dwarf birch in the bryophytes of the Karkonosze Mountains and the Linje peat bog in Kuyavia. Others are newcomers brought here by man and/or benefiting from anthropogenic habitat transformations, e.g.: the Variegated and Bukhansha racemes from the Black Sea basin.
Sometimes the status of a particular species at a particular site raises disputes among experts. Examples are the smotrava specimen in the Bieszczady Mountains or the mud crayfish in the waters of Central Poland. This is not a purely academic discussion! Relict species and their habitats are covered by various forms of species and area protection. Alien species, on the other hand, meet a completely different fate – they are sometimes eradicated ex officio, or at least their further spread is mitigated. Both types of measures entail new responsibilities for investors, conservation services, local governments, anglers, and finally all citizens.
A great example of this type of problem is the discussion that has been going on for 15 years about the status of the grass snake Natrix tesselata in Poland. On the scale of Eurasia, it is still a fairly common species, widely distributed from Western Europe to western China, in climates slightly warmer than Poland, and associated with aquatic environments even more strongly than the familiar grass snake Natrix natrix [1, 4, 5, 7, 8].
The species’ northern range extends to, among other places. Don in Russia, Ukraine, Slovakia, the Czech Republic and Germany. This year marks the 10th anniversary of its inclusion in the list of species protected by law in Poland(Regulation 2014, 2016). However, voices are not silent that it is an alien newcomer and poses a threat to native fauna and pond management. The protection of the osprey snake is all the more inconceivable, since the status of protected species is still not lived up to by the colchid scavenger Anguis colchica – a species as native as the eastern hedgehog, gray nightingale or forest creeper [7, 9].
Whoever saw, whoever knows…
Keys and atlases of the 20th century, e.g.: Młynarski 1960 or Juszczyk 1987, denied it the status of a native species within the borders of 1945-present Poland, although it occurs wild in neighboring countries. There were also a paucity of poorly documented reports and pure speculation about the possibility of its natural occurrence in our fresh waters. For example, in the 19th century, the famous zoologist (remembered today as an entomologist) Alexander (Sandor) Pongracz was said to have seen it, and even caught it, in Ludynia (today’s Świętokrzyskie Province).
The well-known museologist (and entomologist rather than herpetologist) Stefan Stobiecki in 1883. cited stories from fishermen fishing in streams about the occurrence of the water snake Tropidonotus hydrurus (then a synonym for N. tesselata), perching in crayfish burrows and under stones in streams at the foot of Babia Góra. However, he admitted that he had not seen this reptile species himself [4, 5, 7, 9].
Save the osprey or save from it?
In 2009. The presence of one young specimen was documented in Cieszyn, Poland. The impetus for further searches for N. tesselata came when an overly numerous and previously unknown population was found in Havířov in Czech Silesia, just 10 km from the Polish borders. In 2012. anglers picked up and photographed a sizable individual (0.40-0.45 m) in nearby Pogwizdów (Hażlach commune, Silesian voivodeship). The inability to confirm the osprey’s presence in Poland, and above all doubts about its indigeneity (nativeness) in the Baltic Sea basin, led some herpetologists to call for its removal from the list of legally protected species.
It was not until 2019-2021 that further confident observations of this species could be made at Pogwizdow ponds [9]. The prevalence of juveniles and the nature of the fish farm suggest the existence of a stable, perhaps even developing, population, brought in on fishing equipment or with construction material, stocking or fuel (this is how the much rarer Aesculapian snake spreads in our country). It is less likely (although it cannot be completely ruled out) that there was a deliberate attempt to enrich the domestic fauna, as in the case of the release of green or wall lizards in our country. Or breeding snakes for European collectors and/or traditional Chinese medicine. [5, 7, 8, 9]
It seems unlikely that the young specimens would have traveled nearly 60 km on their own, either by watercourses or along them. This favors the hypothesis of a recent appearance and foreign origin of the pogwizd population. Also, genetic studies of a number of European populations seem to indicate the foreign nature of osprey snakes in Cieszyn Silesia. This is because they show a higher similarity of the newly discovered populations of the Baltic basin with distant evolutionary lines of southern Europe (Austria, Slovenia, Hungary and Romania), rather than with the geographically closest, rather native, populations of Germany, the Czech Republic and Slovakia [6, 8, 9].
More questions than answers
Natrix tesselata has also been listed in inland Poland. At a Warsaw terrarium exchange, one osprey was tried to be sold as an exotic snake. However, the buyer realized that he was dealing with a scaly one native to Europe and protected as a species in Poland, so he notified the Epicrates Foundation from Lublin. The mysterious individual wandered to southeastern Poland and lived out its days there. The seller was from Bielsko-Biala, so it is impossible to exclude the osprey’s capture in Czech or Polish Silesia. Disposal of the fallen individual made genetic testing impossible.
Instead, the body of another specimen, found a few years ago in Krakow, on Majora Street, has been examined. We are waiting for the publication of the results. Analyses of cytochrome c diversity across Europe suggest that during the Pleistocene, populations of N. tesselata reached further north, up to and including Polish lands, disappeared again and again, then expanded again to the rhythm of climate change in successive interglacials. Therefore, the native, relict nature of the Pogwizdów lineage cannot be denied [1, 2, 6, 8].
In the article, I used, among other things. z:
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- GUICKING D., HERZBERG A., WINK M. 2004. Population genetics of the dice snake(Natrix tessellata) in Germany: implications for conservation. Salamander 40, 3: 217-234.
- IOANNIDIS Y., MEBERT K. 2011. Habitat preferences of Natrix tessellata at Strofylia, northwestern Peloponnese, and comparison to syntopic N. natrix. Mertensiella, 18, 302-310.
- KACZMARSKI M. 2015. Gerard Gierlinski, Joanna Grabowska, Michal Grabowski, Radomir Jaskola, Illustrated encyclopedia of amphibians and reptiles of Poland. Fenix Publishing House, 2015 [recenzja]. Cosmos 3(316): 509-513.
- KOLENDA K., SKAWIŃSKI T., KACZMARSKI M. 2019. Review of “new” species of amphibians and reptiles occurring in Poland. Kosmos 68, 1: 209-221.
- MAROSI B., ZINENKO O.I., GHIRA I.V., CRNOBRNJA-ISAILOVIĆ J., LYMBERAKIS P., SOS T., POPESCU O. 2012. Molecular data confirm recent fluctuations of northern border of dice snake(Natrix tessellata) range in Eastern Europe. North. West. J. Zool. 8, 2: 374-377.
- SURA P. 2018. The osprey snake Natrix tessellata (Laurenti, 1768). 120-122. In: GŁOWACIŃSKI Z., SURA P. (Editor). Atlas amphibians and reptiles of Poland. Status – distribution – protection, with keys for determination. Published. PWN, Warsaw.
- VLČEK P., NAJBAR B., JABŁOŃSKI D. 2010. First records of the Dice Snake(Natrix tessellata) from the North-Eastern part of the Czech Republic and Poland. Herpetol. Notes 3: 23-26.
- HARE B., MŁONIEWICZ L., SOLECKI A., MATUSIAK R., DURAJ M.,. & JABŁOŃSKI D. (2022). Stable population of the grass snake Natrix tessellata in Cieszyn Silesia. Nature Review, 33(1): 35-48.