Dice snake
Dice snake | |
---|---|
![]() | |
N. tessellata capturing a Gobius fish. | |
![]() | |
Small (possibly immature) tessellated water snake, Umbria, Italy. | |
Conservation status | |
![]() Least Concern (IUCN 3.1)[1] | |
Scientific classification ![]() | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Order: | Squamata |
Suborder: | Serpentes |
Family: | Colubridae |
Genus: | Natrix |
Species: | N. tessellata |
Binomial name | |
Natrix tessellata (Laurenti, 1768) | |
![]() | |
Distribution of the Natrix tessellata | |
Synonyms | |
Coronella tessellata Laurenti, 1768 |
![](http://upload.wikimedia.org/wikipedia/commons/thumb/9/99/Schlange_frist_Fisch.jpg/230px-Schlange_frist_Fisch.jpg)
The dice snake (Natrix tessellata), also known as the Eurasian, European or tessellated water snake (or simply 'water-snake'), is a species of highly amphibious, aglyphous (non-venomous) squamate (snake) of the water-snake genus Natrix (family Colubridae, subfamily Natricinae).[3]
Brief description
Female dice snakes are bigger than males, as is typical in many snake species; however, the mature size is typically between 1.0–1.3 m (39–51 in) long, for any average specimen. The coloration of their scales varies by region, by habitat, and even by individual, though these snakes are generally a yellowish-gray to an olive-green hue, though some are darker, being a dirty-brown to almost black. Having muted, "plain" colors, with minimal flashy scales, aids the water snake in camouflaging against larger predators (such as storks or raptors), especially when swimming or submerged in murky water; the species' rather subdued coloration also aids the dice snake in stealthily ambushing fish underwater, its primary choice of prey. Additionally, as dice snakes are cold-blooded reptiles, and thus have to consciously adjust their body temperatures, having a darker-colored belly enables them to warm themselves faster and more effectively, simply by laying on a sun-heated rock—naturally, darker colors absorb heat more readily when compared to lighter shades.
N. tessellata is commonly known as the 'dice' snake as its body is patterned with many black spots, somewhat resembling dice (used in gambling or games). The squared, checkered scales on the snake's belly and underside, which may feature a vivid yellow or orange backdrop, also earn the snake its common name.
Biology
Living mainly near rivers, streams and lakes, it frequently feeds on fish. Sometimes, it feeds also on amphibians such as frogs, toads, and tadpoles.
Classified as nonvenomous, N. tessellata produces a potent antihemorrhagin in its serum[4] and has been said to produce a neurotoxin through a gland in its mouth.[5] As a defence, it spreads a very bad-smelling secretion from its cloaca. Another defence mechanism is thanatosis, playing dead.
During the mating season (March–May), they congregate in large groups. Egg-laying is usually in July, and one clutch consists of 10–30 eggs. The young snakes hatch in early September.
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/06/Natrix_tessellata_frombosnia.jpg/230px-Natrix_tessellata_frombosnia.jpg)
![](http://upload.wikimedia.org/wikipedia/commons/thumb/7/79/Sea_Snake.jpg/230px-Sea_Snake.jpg)
Dice snakes hibernate from October to April in dry holes near the water.
Distribution
The dice snake is found throughout much of Eurasia, in climates ranging from hot or semi-arid to temperate with freezing winters. The species is known from Central, South and Western Asia, the Levant, Asia Minor, and the Caucasus region, as well as some parts of the Middle East where permanent sources of water may be located. Additionally, it is known to inhabit the Balkans, Southern Europe, and the general Mediterranean basin regions, as well as portions of Central, Eastern and Western Europe.
The dice snake has been observed in the following countries and regions: Afghanistan, Albania, Armenia, Austria, Azerbaijan, Bosnia and Herzegovina, Bulgaria, (western) China, Croatia, Cyprus, Czech Republic, Egypt, France, Georgia, Germany, Greece, Hungary, India, Iran, Iraq, Israel,[6] Italy, Jordan, Kazakhstan, Kyrgyzstan, Lebanon, Montenegro, North Macedonia, Pakistan, Poland,[7] Romania, Russia, Serbia, Slovakia, Slovenia, Switzerland, Syria, Tajikistan, Turkmenistan, Turkey, Ukraine, Uzbekistan, and Yemen.
Research
Czech Nature Conservation Agency
The dice snake is considered Critically Endangered in the Czech Republic, mostly due to destruction of habitats and the introduction of an invasive species, the American mink. In order to combat this, the Czech Nature Conservation Agency began a project in 2007 to figure out what factors determine the distribution of the dice snake. The predictive model suggested that the most influential factors were watercourses and bodies, average annual temperatures, altitude, slope inclination, and precipitation seasonality. At the conclusion of the study, researchers proposed that the next route of study should be focused on areas that should but don't contain dice snake populations based on the predictive model. These areas might become the focus for conservation/migration efforts.[8]
Fluctuating asymmetry in urban dice snake populations
Urbanization is one of the greatest reasons that habitats for dice snake populations are on the decline. As a result, some dice snake populations have been forced to live in artificial lakeside habitats. A study published in 2023 researched the effects of urban living on the dice snake and found that urban environmental factors influence the fluctuating asymmetry, body condition, and size of dice snake populations.[9]
Fluctuating asymmetry (FA), a measure of developmental instability, was found to be significantly influenced by local environmental variables. Specifically, larger harbors were associated with poorer body condition in dice snakes. This correlation suggests that larger harbors may harbor higher pollutant concentrations or increased human disturbance, leading to adverse effects on snake health and fitness. Proximity to main roads was identified as a significant factor influencing the level of fluctuating asymmetry in dice snake populations. Snakes living closer to main roads exhibited higher levels of asymmetry, indicating potential negative effects of road-related factors on snake development and health.[9]
The study concluded that conservation efforts should focus on mitigating the negative impacts of urbanization on dice snake populations. Strategies may include reducing pollutant release into the environment, exploring alternative road materials to minimize the adverse effects of roads, and implementing measures to reduce human disturbance in snake habitats.[9]
Population bottlenecks and resulting loss of genetic variation
Another study in 2001 studied the effect of bottlenecks on the dice snake population when dice snakes were introduced into several lakes in Switzerland.[10] A bottleneck on a population is "an event that drastically reduces the size of a population"[11]
The study followed two introduced populations, one that was serially bottlenecked and one that was only bottlenecked once. Both populations had much less allelic diversity and resulting heterozygosity (due to inbreeding) than populations that had never been bottlenecked, but the one that was serially bottlenecked displayed a greater severity of these conditions.[10]
Scale anomalies were another factor that was studied during this project. Scale anomalies are often a sign of developmental stress, and the introduced populations had a greater frequency of scale anomalies than normal. The occurrence of scale anomalies correlated with the degree of bottlenecking and individual heterozygosity. Developmental stability, reflected in the ability to withstand environmental and genetic perturbations, is indirectly linked to individual fitness. Studies on other snake species indicate a negative relationship between scale anomalies and traits such as locomotion speed and growth rate, which affect survival.[10]
Researchers argue that population decline should be prevented and large populations maintained in order to conserve allelic diversity and genetic variability. But the root problem of habitat destruction must be addressed as well. Habitat protection and restoration are crucial for protecting natural populations of dice snake. Demographic and genetic monitoring of populations can aid in detecting declines and assessing genetic variability. Introduction of new genes from different populations can enhance genetic variability, but careful selection of source populations is essential to avoid harming existing populations and outbreeding depression.[10]
Parasitic threat
One of the most numerous populations lives in the vicinity of the ruins of Histria, in the Dobruja region, Romania. This population has been recently discovered to be threatened by a parasitic nematode of the genus Eustrongylides. Since 2005, the population from Histria has been receiving researchers' attention. For example, a joint Romanian–Swedish–Czech research program is focused on population biology studies and parasitic threats of this unique coastal population.[12]
References
- ^ Mebert, K.; Amr, Z.S.S.; Al Johany, A.M.H.; Aloufi, A.A.H.; Jiang, J.; Meyer, A.; Sterijovski, B.; Baha El Din, S.; Pleguezuelos, J.; Sá-Sousa, P.; Corti, C.; Ajtic, R.; Tuniyev, S.; Orlov, N.L.; Ananjeva, N.B.; Cogălniceanu, D.; Andrén, C.; Crnobrnja-Isailović, J.; Aghasyan, A.; Avci, A.; Tuniyev, B.; Lymberakis, P.; Wilkinson, J.; Üzüm, N.; Podloucky, R.; Kaya, U.; Vogrin, M.; Pérez Mellado, V.; Cheylan, M.; Nettmann, H.K.; De Haan, C.C.; Schmidt, B.; Lau, M.; Borkin, L.; Milto, K.; Golynsky, E.; Belouskova, A.; Rustamov, A; Nuridjanov, D.; Munkhbayar, K. (2021). "Natrix tessellata". IUCN Red List of Threatened Species. 2021: e.T157256A745071. doi:10.2305/IUCN.UK.2021-2.RLTS.T157256A745071.en. Retrieved 21 February 2022.
- ^ Boulenger, G.A. 1893. Catalogue of the Snakes in the British Museum (Natural History), Volume I. London. pp. 233-234
- ^ Guicking, Daniela; Joger, Ulrich; Wink, Michael (25 August 2009). "Cryptic diversity in a Eurasian water snake (Natrix tessellata, Serpentes: Colubridae): Evidence from mitochondrial sequence data and nuclear ISSR-PCR fingerprinting". Organisms Diversity & Evolution. 9 (3): 201–214. Bibcode:2009ODivE...9..201G. doi:10.1016/j.ode.2009.03.001.
- ^ Borkow, Gadi; Gutierrez, Jose Maria; Ovadia, Michael (December 1994). "A potent antihemorrhagin in the serum of the non-poisonous water snake Natrix tessellata: isolation, characterization and mechanism of neutralization". Biochimica et Biophysica Acta (BBA) - General Subjects. 1201 (3): 482–490. doi:10.1016/0304-4165(94)90080-9. PMID 7803481.
- ^ "Wildest Europe - Swimming Snake". www.facebook.com. Discovery Channel UK. Retrieved 2018-03-17.[unreliable source?]
- ^ Academy, Reptile (2024-04-06). "Natrix tessellata: A Comprehensive Review". לוכד נחשים - מוקד מחוז ירושלים (in Hebrew). Retrieved 2024-04-06.
- ^ Vlcek, Petr; Bartlomiej Najbar and Daniel Jablonski. (2010) First records of the Dice Snake (Natrix tessellata) from the North-Eastern part of the Czech Republic and Poland. Archived 2010-04-14 at the Wayback Machine Herpetology Notes 3:23-26
- ^ Chmelař, Jan; Civiš, Petr; Fischer, David; Frynta, Daniel; Jeřábková, Lenka; Rudolfová, Veronika; Rehák, Ivan (28 December 2023). "Protecting isolated reptile populations outside their main area of distribution: a predictive model of the Dice snake, Natrix tessellata, distribution in the Czech Republic". Biodiversity Data Journal. 11: e114790. doi:10.3897/BDJ.11.e114790. PMC 10767748. PMID 38188184.
- ^ a b c Mészáros, Boglárka; Bürgés, József; Tamás, Mónika; Gál, Blanka; Bohus, Attila; Schmera, Dénes (December 2023). "Effects of the urban environment on the developmental stability, size and body condition of dice snakes (Natrix tessellata) living in artificial lakeside habitats". Ecological Indicators. 156: 111117. Bibcode:2023EcInd.15611117M. doi:10.1016/j.ecolind.2023.111117.
- ^ a b c d Gautschi, Barbara; Widmer, Alex; Joshi, Jasmin; Koella, Jacob C. (September 2002). "Increased frequency of scale anomalies and loss of genetic variation in serially bottlenecked populations of the dice snake, Natrix tessellata". Conservation Genetics. 3 (3): 235–245. doi:10.1023/A:1019924514465.
- ^ "population bottleneck". Scitable. Nature Education.
- ^ Mebert, Konrad (2011). The Dice Snake, Natrix Tessellata: Biology, Distribution and Conservation of a Palaearctic Species. DGHT. ISBN 978-3-9812565-4-3.[page needed]
External links
![](http://upload.wikimedia.org/wikipedia/en/thumb/4/4a/Commons-logo.svg/30px-Commons-logo.svg.png)