Natrix tessellata: A Comprehensive Review


The dice snake (Natrix tessellata) is a widespread Eurasian non-venomous colubrid snake. This review provides a detailed analysis of current knowledge on N. tessellata, encompassing its taxonomy, morphology, distribution, habitat ecology, behavior, reproduction, diet, predators, conservation status, and potential threats. The paper also explores ongoing research avenues and future directions for the study of this fascinating reptile.Snake catchers in Jerusalem make many conservation efforts

1. Introduction

Snakes belonging to the genus Natrix are widely distributed across Eurasia and North Africa. Among them, the dice snake (Natrix tessellata) holds a distinct position due to its vast geographic range, encompassing a large portion of Europe and extending eastward into central Asia [1]. This review aims to comprehensively explore the current scientific understanding of N. tessellata, delving into its evolutionary history, physical characteristics, distribution patterns, ecological preferences, behavioral strategies, reproductive biology, dietary habits, and vulnerability to threats. Additionally, the paper highlights areas requiring further investigation and outlines future research directions for a deeper understanding of this ecologically significant snake species.

2. Taxonomy and Phylogeny

N. tessellata was first described by Josephus Laurenti in 1768 [2]. It belongs to the family Colubridae, subfamily Natricinae, which includes a diverse group of water snakes widely distributed across the globe [3]. Phylogenetic analyses suggest a close relationship between N. tessellata and its congener, the grass snake (Natrix natrix) [4]. However, recent studies based on mitochondrial DNA sequencing have revealed further genetic variation within N. tessellata, potentially indicating the existence of cryptic lineages or subspecies [5].

3. Morphology

N. tessellata exhibits a slender body with a distinct neck and a flattened head. The dorsal scales are strongly keeled, arranged in 19 midbody rows [6]. The ventral scales range from 160 to 197, and the subcaudal scales number between 48 and 86 [7]. Coloration varies considerably across the geographic range, with a typical pattern consisting of a brown or grayish background adorned with a series of dark brown to black squarish or rectangular spots, earning the snake its common name, "dice snake." However, melanistic individuals with entirely black bodies and unpatterned individuals are also documented [8]. The ventral surface is usually pale yellow or cream-colored with dark spots on the throat in some populations [9]. Sexual dimorphism is present, with females generally larger than males, reaching lengths of up to 1.37 meters (54 inches) compared to the male's maximum size of around 1 meter (39 inches) [10].

4. Distribution and Habitat

N. tessellata boasts an impressively vast distribution, stretching across a significant portion of Eurasia. Its range encompasses central and southeastern Europe, extending eastward through Turkey and the Caucasus into central Asia as far east as western China [11]. Further south, it is found in parts of the Middle East, including Iran, Iraq, and Israel [12]. N. tessellata primarily inhabits areas with freshwater bodies, such as rivers, streams, lakes, ponds, and marshes [13]. It demonstrates a preference for well-vegetated riparian zones, often basking on rocks, logs, or emergent vegetation near the water's edge [14]. Interestingly, populations in the Mediterranean region exhibit adaptations to saltwater environments, occasionally venturing into coastal lagoons and brackish waters [15].

5. Habitat Ecology

N. tessellata is a semi-aquatic snake, spending a significant portion of its time near or in water bodies. It is a proficient swimmer, utilizing its laterally flattened tail for propulsion [16]. During the day, it basks in the sun to regulate its body temperature and enhance digestion [17]. At night, it may become more active, especially during warmer seasons, and can be observed foraging on land or in the water [18]. N. tessellata exhibits a strong homing instinct, returning to specific refuges during the winter months to hibernate communally with other individuals [19]. These refuges can include rock crevices, burrows, and anthropogenic structures like abandoned buildings [20].

6. Behavior

N. tessellata displays a range of defensive behaviors when threatened. When startled, it may attempt to flee into the water or coil its body and flatten its head in a display of intimidation [21]. If cornered, it may resort to thanatosis, also known as playing dead, by lying motionless with its tongue hanging out [22]. Additionally, it can release a foul-smelling musk from its cloaca to deter predators [23]. Notably, N. tessellata exhibits a degree of interspecific communication, particularly with its close relative, the grass snake. Studies have

6. Behavior (Continued)

Studies have documented instances where dice snakes and grass snakes appear to recognize and tolerate each other, potentially reducing competition for resources [24]. This behavior suggests a level of social complexity not often observed in solitary reptiles.

7. Reproduction

N. tessellata reaches sexual maturity between 3 and 4 years of age [25]. Mating typically occurs in spring, with males engaging in combat displays and scent marking to establish dominance and compete for females [26]. The female lays a clutch of 4 to 20 eggs in a suitable location, such as a compost heap, rotting vegetation, or loose soil [27]. Incubation lasts for 60 to 70 days, with hatchlings emerging at a length of around 15 to 20 centimeters (6 to 8 inches) [28]. Hatchlings are independent upon emergence and immediately begin hunting for small prey items like tadpoles and insects [29].

8. Diet

N. tessellata is an opportunistic predator, with its diet primarily consisting of aquatic prey. Fish, particularly smaller species, form a significant portion of its food intake [30]. It also preys on amphibians such as frogs, toads, and tadpoles [31]. Occasionally, it may consume small invertebrates like earthworms and aquatic insects [32]. N. tessellata possesses a unique feeding strategy for swallowing prey that is too large to ingest whole. It employs a technique known as "opisthophagy," where it swallows the prey head first, utilizing its flexible lower jaw and keeled teeth to maneuver the food item into its stomach [33].

9. Predators

N. tessellata faces predation pressure from various animals across its range. Avian predators, including raptors like hawks, owls, and kites, pose a significant threat, particularly to young and smaller individuals [34]. Mammals such as foxes, badgers, and hedgehogs may also prey on dice snakes, especially when they encounter them on land while foraging or basking [35]. Additionally, aquatic predators like large fish and some reptile species, including certain turtles, may occasionally consume them [36].

10. Conservation Status

The International Union for the Conservation of Nature (IUCN) currently lists N. tessellata as "Least Concern" due to its widespread distribution and relatively abundant populations in many areas [37]. However, localized threats exist in certain parts of its range. Habitat loss due to degradation of wetlands and riparian zones, pollution of freshwater bodies, and fragmentation of landscapes pose challenges for some populations [38]. Additionally, road mortality can be a significant factor in areas with high traffic volume [39]. Climate change may also have future implications, with potential alterations in precipitation patterns and water availability impacting habitat suitability [40].

11. Threats and Challenges

While not currently classified as threatened, N. tessellata faces several challenges that warrant ongoing monitoring and conservation efforts. Habitat loss and degradation remain prominent threats, particularly in areas experiencing rapid development and agricultural intensification. Public education and awareness campaigns can play a crucial role in promoting the importance of healthy riparian ecosystems and fostering tolerance for snakes like N. tessellata [41]. Additionally, research on the specific impacts of climate change on dice snake populations will be valuable in developing effective conservation strategies for the future.

12. Future Research Directions

Despite the existing body of knowledge on N. tessellata, several areas remain open for further investigation. Studies on the specific dietary preferences of dice snakes across their geographic range can provide valuable insights into their ecological role within different ecosystems [42]. Research on the potential impacts of climate change on prey availability and habitat suitability is crucial for predicting future population trends [43]. Additionally, investigating the role of interspecific communication and social behavior in N. tessellata can offer a deeper understanding of its social complexity [44]. Furthermore, exploring the genetic variation within the species and the possibility of cryptic lineages can inform conservation efforts and population management strategies [45].

13. Conclusion

The dice snake (Natrix tessellata) is a fascinating and ecologically significant reptile species with a vast distribution across Eurasia. This review has compiled current knowledge on its taxonomy, morphology, distribution, habitat ecology, behavior, reproduction, diet, predators, conservation status, and future research directions. N. tessellata exhibits remarkable adaptations for a semi-aquatic lifestyle and plays a vital role in maintaining healthy ecosystems. By addressing existing threats and fostering ongoing research efforts, we can ensure the continued survival of this diverse and resilient snake species.

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