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Natrix
Natrix natrix
Scientific classification Edit this classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Colubridae
Subfamily: Natricinae
Genus: Natrix
Laurenti, 1768
Type species
Natrix natrix

Natrix is a genus of Old World snakes found mainly across Eurasia (although the range of Natrix tessellata extends into Egypt and those of N. astreptophora and N. maura into north-west Africa) in the subfamily Natricinae of the family Colubridae. They are commonly called grass snakes and water snakes, but some other snake species also known commonly as "grass snakes" and "water snakes" are not in the genus.

Species

[edit]

The genus Natrix contains five extant species[1] and at least five extinct (fossil-only) species.

Image Scientific name Common name Distribution
Natrix astreptophora (Seoane, 1885) Iberian grass snake[2] Iberian peninsula (Spain and Portugal), southern France, coastal north-west Africa (Morocco, Algeria, Libya, Tunisia)
Natrix helvetica (Lacépède, 1789) barred grass snake[3] Western Europe, including southern Great Britain
Natrix maura (Linnaeus, 1758) viperine water snake[4] Portugal, Spain, France, north-west Italy and into Switzerland; north-west Africa (Morocco, Algeria, Libya, Tunisia)
Natrix natrix (Linnaeus, 1758) grass snake[4] Mainland Europe from mid Scandinavia to southern Italy, to northern Middle East and Central Asia
Natrix tessellata (Laurenti, 1768) dice snake[4] Much of Eurasia, and Egypt
†Natrix longivertebrata (Szyndlar, 1984) extinct species (Pliocene, Miocene) Poland, Austria, France[5]
†Natrix merkurensis Ivanov, 2002 extinct species (Miocene)[6] Czech Republic, France[7]
†Natrix mlynarskii Rage, 1988 extinct species (Eocene–Miocene) France[8]
†Natrix parva Szyndlar, 1984 extinct species (Miocene) Poland[9]
†Natrix sansaniensis (Lartet, 1851) extinct species (Miocene)[6] Czech Republic, France

Nota bene: A binomial authority in parentheses indicates that the species was originally described in a genus other than Natrix.

Etymology

[edit]

Natrix is classical Latin for a water snake. The word comes from a Proto-Indo-European root meaning "snake", with cognates in the Celtic and Germanic languages, the latter including the English adder. It was probably influenced through folk etymology by the Latin nare and natare meaning "swim";[10][11] it appears to be a grammatically feminine word for "swimmer".

Geography

[edit]

The refuge of a widely distributed Western European lineage regarding the barred grass snake commonly known as Natrix helvetica was most likely located in southern France and outside the classical refuges in the southern European peninsulas. One genetic lineage of the common grass snake (N. natrix) is also distributed in Scandinavia, Central Europe, and the Balkan Peninsula.[12]

References

[edit]

Further reading

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Revisions and contributorsEdit on WikipediaRead on Wikipedia

Natrix

View on Grokipedia
from Grokipedia
Natrix is a of semi-aquatic, non-venomous snakes belonging to the Natricinae within the Colubridae, encompassing five extant species primarily distributed across the from northwestern to temperate and extending eastward to and . These snakes, often referred to as grass snakes or water snakes, are characterized by their slender bodies, distinct heads, and keeled dorsal scales arranged in 17–23 rows, with adults typically measuring around 1 meter in length, though some can reach up to 2 meters. The species within Natrix include the barred grass snake (N. helvetica), the viperine water snake (N. maura), the (N. tessellata), the eastern grass snake (N. natrix), and the Iberian-Maghrebi grass snake (N. astreptophora), each adapted to freshwater habitats such as rivers, lakes, marshes, and coastal wetlands, where they exhibit diurnal activity and strong swimming abilities. Ecologically, they play a key role as predators, feeding predominantly on amphibians like frogs and toads, as well as , small mammals, and occasionally birds or , with females laying clutches of 10–40 eggs in moist, hidden sites during summer. Their distribution reflects post-glacial recolonization patterns, with some species showing into distinct lineages adapted to regional climates, and they are generally classified as Least Concern by conservation assessments due to their wide ranges, though habitat loss poses localized threats.

Taxonomy

Classification

The genus Natrix is classified within the kingdom Animalia, Chordata, class Reptilia, order Squamata, suborder Serpentes, Colubridae, and subfamily Natricinae. The genus was established by Josephus Nicolaus Laurenti in 1768, with Natrix natrix designated as the (originally described as Coluber natrix by Linnaeus in 1758). Phylogenetically, Natrix forms a monophyletic group within the subfamily, closely related to other Eurasian natricine genera such as Rhabdophis and Amphiesma (formerly grouped under Tropidonotus in older classifications). Molecular analyses, including sequences from mitochondrial genes like 16S rRNA and , have robustly supported this , revealing Natrix as a distinct that diverged during the . These studies highlight the genus's evolutionary ties to semiaquatic colubrids in the Palearctic . Taxonomic revisions in recent decades have refined the genus's composition, notably elevating former subspecies to species level based on integrated genetic and morphological data. For instance, in 2017, the barred grass snake (Natrix helvetica) was recognized as a full species distinct from N. natrix, supported by mitochondrial DNA phylogenies showing deep divergence and limited hybridization across contact zones like the Rhine River. Currently, Natrix includes five extant species: N. astreptophora, N. helvetica, N. maura, N. natrix, and N. tessellata. The fossil record documents at least five extinct species, such as N. longivertebrata from the Neogene, indicating a longer evolutionary history in Europe.

Etymology

The genus name Natrix derives from the classical Latin nātrīx, meaning "water snake" or "swimming snake," reflecting the semi-aquatic habits of many in the . This term traces back to the *(s)nh₁-tr-ih₂-, denoting "snake," with cognates in other such as Old High German natar (viper) and English "." The suffix in nātrīx likely emphasizes an aquatic association, distinguishing it from more general Latin terms for snakes like serpens. The genus Natrix was formally established by Austrian naturalist Josephus Nicolaus Laurenti in his 1768 publication Specimen Medicum, Exhibens Synopsin Reptilium Emendatam cum Experimentis Circa Venena et Antidota Reptilium Austriacorum, where he classified several snake under this name. Laurenti's nomenclature drew influence from ancient Roman descriptions of natricine snakes in works by authors like , who referenced similar aquatic colubrids in texts. Species within Natrix bear common names that highlight their habitats and appearances, such as "grass snake" for the more terrestrial N. natrix and "viperine water snake" for the semi-aquatic N. maura. Regional variations include "ringed snake" for N. natrix in parts of , alluding to its distinctive yellow collar pattern. To avoid confusion, Natrix species should be distinguished from North American "water snakes" in the genus Nerodia, which were formerly classified under Natrix but separated based on phylogenetic differences in the 1970s; Nerodia represents a distinct lineage within the subfamily.

Description

Physical Characteristics

Natrix species are medium-sized colubrid snakes characterized by a slender, cylindrical body form adapted for semi-aquatic and . Their dorsal scales are keeled and arranged in 17-23 rows at mid-body, providing some texture for grip on varied substrates, while the anal scale is divided. Females are typically larger than males, with adults generally reaching 60–150 cm in total length, though exceptional individuals can exceed 2 m, as recorded in N. natrix; neonates hatch at 11–22 cm. The head is distinctly separated from the neck, featuring large eyes with round pupils indicative of diurnal vision, and lacking heat-sensing pits typical of pit vipers. These snakes are non-ous rear-fanged colubrids, with no enlarged rear fangs for delivery. They have 155–189 ventral scales along the body. Males possess hemipenes for copulation, and the exhibits an oviparous involving egg-laying. Sensory adaptations in Natrix emphasize chemical and visual cues suited to their active lifestyle. The Jacobson's organ, a vomeronasal structure, facilitates chemoreception by processing scents gathered via the forked tongue. Their eyesight supports diurnal foraging, with round pupils allowing better light regulation compared to nocturnal species.

Coloration and Patterns

Species in the genus Natrix exhibit a range of dorsal colorations, typically olive-green, brown, or gray, which provide effective camouflage in their wetland and riparian habitats. The ventral surface is generally yellowish or white, often marked with a black checkered pattern that aids in blending with substrate during foraging. These base colors vary geographically and by species, with northern populations tending toward darker gray tones and southern ones showing more reddish or olive hues. Common patterns include transverse bands, spots, or blotches arranged in four longitudinal rows along the dorsum, creating a mottled appearance that disrupts the snake's outline. Many feature a distinct , , or orange collar bordered in behind the head, serving as a key identifying trait. For instance, N. tessellata displays a more tessellated pattern of alternating dark and light scales. Melanistic forms, where the body is predominantly , and rare albino variants with reduced pigmentation are documented across the genus, though they occur sporadically and increase in frequency at higher latitudes. Dorsal scales in Natrix are weakly to strongly keeled, arranged in 17–23 rows at midbody, contributing to a relatively smooth gliding motion over surfaces despite the keeling. This scale structure, combined with the cryptic coloration, supports predation by minimizing visibility to prey and predators in vegetated or aquatic environments. Sexual dichromatism is minimal, with no pronounced color differences between sexes, though subtle variations in brightness may occur in males during the breeding season in some populations. Ontogenetic changes are evident, particularly in juveniles, which often display bolder patterns and more contrasting collars for enhanced against avian and mammalian predators. In adults, these markings typically fade, resulting in a more uniform coloration that aligns with their larger size and altered microhabitat use. Such shifts are observed across species like N. helvetica and N. astreptophora, where juvenile spots diminish with age.

Distribution and Habitat

Geographic Range

The genus Natrix is primarily distributed across the Palearctic region, encompassing temperate from —including the and the —eastward to and , with northern limits reaching southern and southern extensions into and northwest . This range spans diverse continental areas without evidence of transoceanic dispersal, relying instead on land bridges for expansion. Biogeographically, the genus dominates temperate Eurasian zones, with disjunct populations in , such as N. maura in . For instance, N. tessellata extends to , marking the southernmost extent in Africa. The historical spread involved post-glacial colonization of approximately 10,000 years ago, originating from Mediterranean and Caucasian refugia, with expansions following river systems like the into . Introduced populations are rare and typically not established; for example, N. maura was likely introduced to by human activity, while escapes in non-native areas like UK islands have not led to viable populations. is particularly high in the Mediterranean, with distinct clades restricted to the and Ibero-Maghrebian regions, such as N. astreptophora.

Habitat Preferences

Natrix snakes, as a , exhibit semi-aquatic to terrestrial lifestyles, with a strong dependence on proximity to permanent or semi-permanent water bodies such as rivers, , lakes, ponds, marshes, swamps, and coastal wetlands for , , and shelter. These habitats provide essential and opportunities for basking on emergent or banks, while surrounding terrestrial areas support movement and refuge. In terms of vegetation, the favors diverse landscapes including temperate forests, grasslands, mixed woodlands, dense scrublands, and riverine corridors, often selecting sunny, open micros with ample cover such as reed beds, fallen logs, dense undergrowth, or rocky outcrops for concealment and . Species show a marked preference for ecotones and habitat edges over dense interiors like closed-canopy forests or intensively cropped fields. Climatically, Natrix species are adapted to temperate zones characterized by mild winters and moderate , typically avoiding arid deserts or extreme cold beyond their range; occurs during colder months (November to February) in sheltered sites like burrows, rock fissures, cellars, or even underwater in milder conditions, with activity resuming in spring (March to October). The altitudinal distribution extends from up to 2,000–3,200 meters, encompassing lowlands to montane regions but excluding high-altitude extremes or hyper-arid environments. Natrix tolerates certain human-modified habitats, such as agricultural farmlands, ditches, ponds, and humid meadows, where they can exploit altered water sources; however, they are sensitive to habitat degradation from drainage schemes, , and , which reduce suitable availability and affect body condition. Species within the genus display some variation in habitat use, with more aquatic preferences in species like N. maura compared to the semi-aquatic N. natrix.

Behavior

Activity Patterns

Species of the Natrix are primarily diurnal, and basking during daylight hours to regulate body temperature and capture prey, with activity peaking in the morning and afternoon in temperate regions. They frequently bask in open sunlit areas to achieve preferred body temperatures around 30–34°C, which optimize locomotion and . In hotter climates, some species shift toward crepuscular or nocturnal patterns to avoid midday heat, as evidenced in N. tessellata, and recent observations (as of 2024) indicate occasional nocturnal activity in N. natrix under certain conditions such as warmer nights or urban environments. In temperate zones, Natrix species follow a distinct seasonal cycle, emerging from brumation sites in early spring (typically –) and remaining active through autumn (–), with inactivity during winter lasting approximately 5–7 months when temperatures drop below 10°C. Brumation occurs in communal hibernacula such as burrows or rock crevices, where metabolic rates decrease significantly to conserve energy. Activity levels are highest from May to , aligning with warmer weather that supports and growth. Movement patterns in Natrix are generally territorial yet flexible, with individuals maintaining home ranges of 0.3–5 hectares, though linear distances traveled can reach up to 500 meters daily during active periods. Seasonal migrations occur, particularly to aquatic habitats for breeding, but snakes return to established ranges afterward. On land, locomotion involves lateral undulation for efficient travel over and soil, while in , they employ side-to-side undulating motions for ; climbing on low is occasional but not a primary mode. Optimal activity temperatures range from 25–35°C, within which and movement efficiency peak; below 18°C or above 35°C, snakes reduce activity, seeking refuge by burrowing into or submerging in to avoid . For instance, N. tessellata may exhibit increased nocturnal activity in warmer southern ranges to mitigate daytime overheating.

Defense Mechanisms

Species in the genus Natrix employ a suite of anti-predator strategies that emphasize evasion, , and chemical deterrence, reflecting their non-venomous nature and reliance on behavioral adaptations for survival. Primary defenses include the release of foul-smelling from cloacal glands, thanatosis (feigning ), and bluffing displays that mimic more dangerous species. These tactics are particularly effective against avian and mammalian predators, allowing many individuals to escape unharmed, though they offer limited protection from human activities such as road traffic. A key chemical defense is the cloacal discharge of malodorous produced by anal glands, which serves to repel close-range threats by creating an unpleasant odor and sticky coating on the predator. This behavior is widespread across Natrix species; for instance, the (N. tessellata) frequently everts its and smears during capture, combining it with other displays for enhanced deterrence. In grass snakes (N. natrix and N. helvetica), musking often accompanies handling or restraint, providing a non-lethal barrier against mammalian predators like foxes or . The secretion's insecticidal properties may also prevent secondary infections from post-release. Thanatosis represents a passive yet dramatic defense, where individuals feign to convince predators that the prey is unpalatable or already deceased. In N. natrix, this involves inverting the body to expose the bright yellow ventral side, gaping the mouth with the tongue protruded, and remaining immobile for minutes to hours, often after initial escape attempts fail. The (N. tessellata) exhibits an elaborate version, incorporating cloacal and even cloacal bleeding () to simulate decay, which has been shown to reduce predator interest in experimental settings. This strategy is more common in adults than hatchlings and correlates with lower attack persistence from predators like birds. Studies suggest that feigning can increase survival in simulated predatory encounters. Physical evasion prioritizes flight over confrontation, with Natrix species leveraging their agility for rapid escape. Semi-aquatic forms like the and viperine snake (N. maura) excel at swift swimming to reach water refuges, while terrestrial species such as the climb vegetation or burrow into cover. Tail thrashing accompanies these efforts, distracting attackers and aiding disentanglement without true , as Natrix lack the regenerative caudal structures seen in some . These maneuvers are most effective in open habitats, allowing evasion from many initial predatory encounters in field observations. Bluff displays further enhance survival by intimidating potential threats through morphological exaggeration. Hissing and neck flattening, observed in N. helvetica and N. maura, mimic the hooding of venomous vipers, potentially serving as to deter visually oriented predators. Mouth gaping reveals enlarged teeth associated with mildly toxic Duvernoy's gland secretions, bluffing venomous capability despite the saliva's low potency. These displays are size-dependent, with larger individuals more likely to employ them aggressively. Coloration patterns, which integrate for initial hiding, support these tactics by breaking the outline during static threats (see Coloration and Patterns section). Overall, these mechanisms contribute to moderate to high efficacy against natural predators. However, anthropogenic threats like collisions bypass these defenses, leading to significant mortality in populated areas.

Ecology

Diet and Predation

Species of the genus Natrix are opportunistic carnivores, with diets dominated by amphibians and , supplemented by small mammals and depending on availability and habitat. In N. natrix (), anurans account for approximately 63% of prey items, small mammals 25%, 10%, and birds 1%, reflecting a generalist feeding strategy influenced by local prey abundance. Conversely, N. tessellata () is more specialized, with comprising over 80% of its diet across 87 taxa, while amphibians and other vertebrates make up the remaining 20%, particularly in arid or montane regions where are scarce. N. maura (viperine snake) shows a similar pattern, with amphibians constituting 86.6% of consumed prey. Prey selection varies seasonally; for instance, N. natrix targets during spring spawning, shifts to newts in summer, and focuses on frogs and toads from onward. Hunting occurs via tactics or active pursuit in both aquatic and terrestrial settings, leveraging the snakes' lifestyle for access to prey. Natrix species typically swallow prey alive but may employ for larger items or mild from the Duvernoy's gland—a posterior oral gland producing toxins that aid in immobilization without rapid lethality. Prey size generally reaches up to 50% of the snake's body length, with larger individuals consuming bigger items while smaller snakes (<400 mm snout-vent length) focus on juveniles or tadpoles. As predators, Natrix snakes face threats from such as hawks and , mammals including foxes, and larger reptiles, with juveniles experiencing particularly high mortality rates due to their vulnerability. Ecologically, they play a key role in controlling and populations in and riparian zones, helping maintain balance in aquatic food webs; their dependence on healthy amphibian communities also positions them as bioindicators of wetland integrity.

Reproduction

Natrix species exhibit a polygynous , in which males compete for access to females during the spring breeding season, typically from to . Male-male often involves ritualized combat behaviors, such as body twining and wrestling, where larger males tend to achieve greater success within aggregations known as mating balls. These interactions align with the snakes' seasonal activity patterns, peaking shortly after emergence from . All in the genus Natrix are oviparous, with females producing a single of eggs annually. Clutch sizes typically range from 10 to 40 eggs, though this varies with female body size and environmental conditions, with larger females laying more eggs. Eggs are laid in or , measuring 2-3 cm in length with soft, leathery shells, and are deposited in communal nesting sites such as rotting , manure heaps, or compost piles that provide suitable humidity and heat. Incubation occurs externally in these warm, humid microhabitats, with optimal temperatures around 25-30°C facilitating embryonic development. Hatching takes 4-10 weeks, depending on temperature, with higher temperatures accelerating the process but potentially affecting hatchling morphology if extremes are reached. Females provide no parental care after oviposition, leaving eggs vulnerable to high predation rates by mammals, birds, and other reptiles. Sexual maturity is reached at 3-5 years of age, corresponding to a snout-vent length of approximately 50-70 cm, after which individuals breed annually. In the wild, Natrix snakes have a lifespan of 10-15 years, though captives can live up to 25 years under optimal conditions.

Species

Extant Species

The genus Natrix comprises five extant species of non-venomous colubrid snakes in the subfamily , primarily distributed across , western Asia, and northwestern . These species exhibit varying degrees of semi-aquatic habits, with distinct morphological and ecological adaptations. Natrix astreptophora, known as the Iberian grass snake or red-eyed grass snake, is characterized by a reddish iris, reduced ventral scale counts (typically 150-170), and a dorsal pattern of alternating dark oval spots or bold bands on an olive-gray background; it inhabits wetlands and grasslands in the , , and northwestern (Morocco, , ), reaching lengths up to 100 cm. Natrix helvetica, the barred grass snake, features a distinctive barred or dorsal pattern, yellow collar, and black dorsal spots; it occurs in western and central including the , , west of the , , and northern Spain, with adults typically measuring 90-150 cm. Natrix maura, the viperine water snake, has a slender body, viper-like head shape, and often uniform grayish or olive dorsal coloration with faint bands; it is the most aquatic species, favoring rivers and lakes in the , , (Sardinia), and northwestern , growing to about 80-100 cm and specializing in a fish-based diet. Natrix natrix, the common grass snake, displays a variable olive-green to brown dorsum with a prominent yellow or white collar and dark vertebral stripe; it ranges widely from Scandinavia and western (east of the ) across central and eastern to western Asia (including parts of Russia, the Middle East, and northwestern China), attaining lengths of 100-150 cm (up to 205 cm maximum) and primarily preying on amphibians. Natrix tessellata, the dice snake, exhibits a checkered or tessellated dorsal pattern of dark spots on a grayish to yellowish background, adapted for camouflage in aquatic environments; it inhabits rivers, lakes, and coasts from central through eastern and western Asia to northeastern Egypt and northwestern China, reaching 100-130 cm and being predominantly piscivorous. Key differences among the species include habitat affinity and trophic specialization: N. maura and N. tessellata are highly aquatic and fish-oriented, while N. natrix and N. helvetica are more terrestrial with amphibian-focused diets; N. astreptophora shows intermediate traits with bolder patterning for open habitats. The following table summarizes comparative traits:
SpeciesMaximum Size (cm)Dorsal PatternPrimary DietGeographic Range
N. astreptophora100Bold bands or oval spotsAmphibians, fishIberia, S France, NW Africa
N. helvetica150Barred or zigzagAmphibiansW/C Europe, UK, N Spain
N. maura100Faint bands, uniform oliveFishIberia, S France, NW Africa, Sardinia
N. natrix150 (max 205)Yellow collar, vertebral stripeAmphibiansEurope (east of Rhine) to W Asia
N. tessellata130Checkered/tessellated spotsFishC/E Europe to W Asia, NE Egypt
Data compiled from species accounts. The genus includes approximately 20 subspecies across its species, reflecting regional morphological variation; notable examples include N. helvetica sicula ( and ), N. natrix scutata ( and ), and N. astreptophora algerica ( and ). Among these, the Cyprus population (N. n. cypriaca) is recognized as a critically endangered subspecies (as of 2021), confined to temporary wetlands on the island and threatened by loss. Recent taxonomic revisions have clarified species boundaries through genetic analyses; for instance, N. helvetica was elevated from a subspecies of N. natrix in 2017 based on divergence exceeding 5% and nuclear markers indicating ancient separation (ca. 3.5 million years ago), with the hybrid zone along the River. Similarly, N. astreptophora was distinguished as a full in 2016 using multilocus , confirming its isolation from N. helvetica despite in .

Extinct Species

The fossil record of the genus Natrix spans from the Early Miocene to the Pleistocene, documenting approximately 10-15 named extinct species primarily from European deposits, with the temporal range extending from about 20 million years ago to 10,000 years ago. These fossils reveal an early diversification of natricine snakes in aquatic and semi-aquatic environments, with key occurrences in central and western Europe, including sites in the Czech Republic, Poland, France, and Hungary. Asian records, such as Pliocene fossils from Moldova, indicate a broader historical distribution before the Pleistocene. Notable extinct species include Natrix merkurensis Ivanov, 2002, from the Early (MN 3a) Merkur-North locality in the , representing one of the earliest records and characterized by vertebrae with moderately developed subcentral ridges. Natrix sansaniensis (Lartet, 1851), known from Middle sites like Sansan in , features typical Natrix-like vertebral morphology, including a bulky centrum and low neural arch, and marks an early appearance of the in . Natrix rudabanyaensis Szyndlar, 2005, from the Late (MN 9) of Rudabánya, , is a small-sized form with rounded haemal keels, suggesting to forested habitats. Further examples encompass Natrix longivertebrata Szyndlar, 1984, which has one of the longest stratigraphic ranges among fossil colubrids, from the to Upper across sites in , , and , with elongated vertebrae (centrum length 4.27–5.58 mm) indicating a transitional form toward extant N. natrix. Natrix parva Szyndlar, 1984, from deposits in (possibly extending to ), is distinguished by its small size and straight hypapophyses, though its taxonomic status remains debated due to limited material. These species often co-occur with fossils of amphibians and in fluvial and lacustrine sediments, pointing to paleoenvironments dominated by ancient wetlands and riparian forests. Evolutionary trends in the Natrix fossil record show a progression toward greater body size and enhanced aquatic specialization, with vertebral features like deepened prezygapophyseal accessory processes evolving from ancestors. The of many pre-Pleistocene forms, including N. longivertebrata and N. rudabanyaensis, correlates with post-Pleistocene cooling and , reducing suitable areas across . This paleontological evidence underscores the genus's resilience, as surviving lineages adapted to changing conditions leading to modern diversity.

Conservation

Status Across Species

The genus Natrix comprises species that are predominantly assessed as Least Concern (LC) on the as of the latest assessments (e.g., 2021), reflecting their wide distributions across and , though many populations exhibit fragmentation and local declines due to alterations. For instance, N. natrix (now often split into N. helvetica in , recognized as a distinct species since 2017) is classified as LC globally and in , but regional assessments indicate vulnerability in isolated populations, such as in the where it is considered a priority species under the with evidence of population declines. Recent European Red List updates (2025) confirm stable LC status for N. helvetica. Species-specific statuses vary, with most remaining stable or LC but certain taxa facing heightened risks. N. helvetica, the of , is LC overall, but the N. h. cetti is classified as Endangered due to its restricted range and ongoing loss in . N. maura, the viperine snake, is LC across its Iberian and North African range, with stable populations in core habitats. N. tessellata, the , is also LC but with a decreasing trend noted in peripheral populations, such as in the where degradation has led to local extirpations and a national status of Critically Endangered. N. astreptophora, the Iberian grass snake, lacks a global IUCN assessment but is regarded as LC in and , though vulnerable in parts of Iberia due to agricultural intensification affecting riparian zones. The N. n. cypriaca () stands out as Critically Endangered, with sparse populations confined to ephemeral on and recent evidence of local extinctions, prompting calls for its formal inclusion on the . Population trends across the genus show stability in core Eurasian ranges but declines in peripheral and fragmented areas where wetland loss has reduced suitable habitats over recent decades. These declines are most pronounced in isolated populations, such as those of N. helvetica in the UK and N. tessellata in , while central Asian and eastern European core areas remain relatively secure. Several Natrix species receive legal protections under European frameworks, including Annex V of the EU , which mandates strict regulation of exploitation for N. helvetica, N. tessellata, N. maura, and N. astreptophora to maintain favorable conservation status in designated sites. Additionally, they are listed under Appendices II and III of the Bern Convention, affording protection against deliberate killing or trade in signatory countries. Conservation monitoring relies on initiatives and genetic studies to assess viability, such as ongoing surveys by the and Reptile Groups of the (ARG ) for N. helvetica and targeted population censuses for N. n. cypriaca using and field observations to track in small, isolated groups.

Threats and Protection

Natrix species face significant anthropogenic threats that contribute to population declines across their range. , primarily through drainage and , is a leading risk, fragmenting essential aquatic and riparian environments critical for and . mortality exacerbates this issue, with vehicles causing high rates of fatalities, particularly among juveniles dispersing from natal sites; studies on Natrix natrix have recorded mortality peaks exceeding 200 individuals per kilometer annually on suburban roads. driven by misconceptions of venomousness leads to illegal killings, as these non-venomous colubrids are often targeted out of fear in rural and urban fringes. Secondary threats include , which disrupts cycles and breeding ; long-term data from northern populations of N. natrix indicate shifts in survival rates and body size linked to warming temperatures. from pesticides diminishes prey availability, such as amphibians, while introduce competition for resources in altered habitats. These factors compound , reducing overall population viability. Conservation efforts emphasize habitat restoration through initiatives like the EU LIFE projects, which have targeted recovery and landscape connectivity in regions such as to benefit Natrix populations. Education campaigns aim to dispel myths about snake danger, reducing persecution, while programs for endangered , including the Cyprus grass snake (N. natrix cypriaca), have been established since around 2010 to bolster genetic stocks and support reintroductions. In protected areas like the Biosphere Reserve, enhanced management has contributed to favorable conservation statuses for N. tessellata through population stabilization and habitat safeguards. Successes include observed recoveries in isolated populations within restored wetlands, such as those for N. tessellata , where protected zones have facilitated increased abundances amid broader declines elsewhere. Looking ahead, creating corridors is essential to enhance connectivity between fragmented habitats, while ongoing research into will inform targeted interventions to maintain adaptive potential in the face of escalating environmental pressures.

References

  1. https://reptile-database.reptarium.cz/advanced_search?genus=Natrix&exact%5B0%5D=genus&submit=Search
  2. https://www.danieljablonski.com/a/soubory/grass%20snakes_natrix_natrix_group_aquatic%20snakes_250523.pdf
  3. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/natrix
  4. https://doi.org/10.1093/cz/zoad008
  5. http://reptile-database.reptarium.cz/search.php?submit=Search&genus=Natrix
  6. https://reptile-database.reptarium.cz/species?genus=natrix&species=natrix
  7. https://academic.oup.com/biolinnean/article-abstract/87/1/127/2691663
  8. https://www.nature.com/articles/s41598-017-07847-9
  9. http://reptile-database.reptarium.cz/advanced_search?genus=Natrix&exact%5B0%5D=genus&submit=Search
  10. https://www.researchgate.net/publication/281589987_Natrix_longivertebrata_from_the_European_Neogene_a_snake_with_one_of_the_longest_known_stratigraphic_ranges
  11. https://reptile-database.reptarium.cz/species?genus=Natrix&species=natrix
  12. https://en.wiktionary.org/wiki/natrix
  13. https://ddescholar.acemap.info/field/2023241457
  14. http://www.animalbase.uni-goettingen.de/zooweb/servlet/AnimalBase/home/reference?id=1194
  15. https://www.researchgate.net/publication/364284689_The_reptiles_of_Turkiye_An_etymology
  16. https://reptile-database.reptarium.cz/species?genus=Natrix&species=maura
  17. https://www.inaturalist.org/taxa/29342-Natrix-natrix-natrix
  18. https://repfocus.dk/Nerodia.html
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