Natrix astreptophora soumiafahdae, Mármol & Geniez & Neumann & Glaw & Fritz, 2025

Natrix astreptophora soumiafahdae subsp. nov.

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Holotype. Naturhistorisches Museum Wien , NMW 32908 View Materials ( Fig. 8 View FIGURE 8 ), young adult (male?), Middle Atlas [ Morocco], don. Erich Sochurek, 6 June 1982.

Paratypes. Collection BEV (housed in the CEFE-CNRS of Montpellier), BEV.6431 (adult female) and BEV.6432 (adult male), stream west of Oulmès, 33.4412, -6.0394, 1,069 m a.s.l. ( Middle Atlas, Morocco), leg. Jean Garzoni 1964 ( Fig. 9 View FIGURE 9 ) .

Diagnosis. A medium-sized grass snake, with a known maximum TL of 133 cm in females and 95 cm in males; tail relatively long, representing 22–26% of TL. Iris red-colored. Differs from Natrix helvetica and N. natrix by the presence of a speckled dorsal pattern without pronounced side-bars, the bicolored pileus in hatchlings and small juveniles, and the red-colored eyes. Differs from N. a. algerica by the closed light neck collar and the presence of black dorsal and lateral markings in adults, except for very large aged females. Differs from most N. a. astreptophora by the presence of light spots on the parietal scales, the light color of the upper postocular scale, and the big black spot on the pileus that only disappears in aged individuals, whereas in N. a. astreptophora it is only present in some hatchlings.

Description of the alcohol-preserved holotype. SVL 49.4 cm, 15.4 cm TaL, corresponding to a TL of 64.8 cm; the tail represents approximately 23.8% of the TL. Body robust, with 19 longitudinal rows of keeled dorsal scales at midbody, 171 smooth ventral scales, 76 pairs of smooth subcaudal scales, anal scale smooth and divided. Body coloration greenish grey with two dorsal rows and two lateral rows of approximately 50 dark markings, those in the dorsal region smaller than the lateral ones. Venter: anterior half of the body yellow with large black quadrangular markings, posterior half of the body inclusive of tail almost completely black. Head well differentiated from body, with big eyes; pholidosis: on both sides, nasal scale divided, 1 loreal, 1 preocular, 3 postoculars, 1 anterior temporal, 2 posterior temporals. Dorsally closed light collar in the neck. Pileus bicolored; brown anteriorly and black posteriorly. In front of the white collar supralabial scales with broad black seams, on each side a large black blotch present, extending downwards from the black pileus spot. Two small round greenish spots on parietal scales.

Variation. The adult female paratype (BEV.6431) has a SVL of 106 cm; its estimated TL is 130 cm (tail incomplete); 19 scale rows at midbody and 168 ventrals are present, subcaudals were not counted; the body has a long slit ventrally ( Fig. 9 View FIGURE 9 ). The SVL of the adult male paratype (BEV.6432) is 75 cm, its TL is 98 cm; the TaL of 23 cm represents 23.4% of the TL. Nineteen scale rows are present at midbody, and there are 166 ventrals and 73 subcaudals. BEV.6432 is the largest known male of this subspecies; BEV.6431 is close to the largest known female (TL 133 cm; Fahd 2001). As in all grass snakes, the snout of N. a. soumiafahdae subsp. nov. is rounded, and there are 7 (rarely 8) supralabial scales on each side of the head, the 3 rd and 4 th supralabials are in contact with the eye. Generally, there are 1 (rarely 2) loreal scale, 1 preocular scale, 3 postocular scales, 1+2 temporal scales, and 19 rows of dorsal scales at midbody, which are keeled, the anal scale is divided. Aged females may have a very big head ( Figs 9 View FIGURE 9 , 10 View FIGURE 10 ). The contrasting hatchling coloration is present at least until an age of 3 years, i.e., the bicolored pileus as described above, the contrasting body pattern, and a well-pronounced light collar posteriorly bordered by two black blotches. In individuals exceeding 70 cm TL (i.e., older than 3 years) the collar fades and the head turns greyish to greenish, so that the pattern may disappear in older individuals.Among the ten adult specimens examined for coloration, the collar and the adjacent black blotches have completely faded out in three very large aged females, and only the lateral black body spots are still slightly visible in one specimen ( Figs 9 View FIGURE 9 , 10 View FIGURE 10 ).

Natrix astreptophora soumiafahdae subsp. nov. resembles N. a. algerica in that the dark part of the bicolored pileus persists much longer during ontogeny than in the nominotypical subspecies. As outlined above, in European hatchlings and small juveniles, the pileus can be even unicolored, a trait we did not observe in any North African specimens. The largest measured Moroccan grass snake with a bicolored pileus has a TL of 70 cm. As in N. a. algerica, Moroccan grass snakes always have the loreal scales black or almost entirely black, whereas in N. a. astreptophora individuals with light colored loreal occur. In all N. a. algerica hatchlings (n=4) and in all Moroccan hatchlings, juveniles, and young adults (n=8) the parietal scales bear light spots. Only 1.2% of the 920 studied N. a. astreptophora have such light spots. Furthermore, the upper postocular scale is always whitish or pure white, like the collar, in Moroccan and Algerian-Tunisian specimens. In contrast, in N. a. astreptophora the upper postocular has the same color as the supraocular scales. A unique trait of the Moroccan grass snakes is that the collar is always closed, without dorsal interruption as in N. a. astreptophora and N. a. algerica. This was already highlighted by Fahd (2001) and confirmed in the present study. In many N. a. astreptophora and in all known N. a. algerica, the collar is in its dorsal center interrupted by at least one dark scale.

Fahd (2001) reported for three males a ventral scale count of 167–173 and for two females, 166. We counted in the male and female paratypes from Oulmès 166 and 168 ventrals. A male from Moulay Abdeslam had 170 ventrals, a female from the same locality, 166, and the holotype from the Middle Atlas has 171 ventrals. This suggests that Moroccan N. astreptophora have more ventral scales than the nominotypical subspecies (maximum of 166; Pokrant et al. 2016). However, J.P. González de la Vega informed us of three Andalusian grass snakes with 170 and 175 ventral scales, and E. Fernández Meléndez found two specimens with 167 and 170 ventral scales in Andalusia. For a comparison of ventral counts of N. a. algerica, see above .

Etymology. We dedicate the new subspecies to the Moroccan herpetologist Soumia Fahd, who contributed significantly to the knowledge of Moroccan grass snakes in her doctoral thesis (Fahd 2001) and publications ( Fahd & Pleguezuelos 1992, 2001; Mediani et al. 2015).

Biogeography. Natrix astreptophora soumiafahdae subsp. nov. is only known from Morocco. Together with its counterpart N. a. algerica in Algeria and Tunisia, its distribution pattern matches a well-known phylogeographical paradigm for the Maghreb, with two deeply divergent lineages, (1) in Morocco west of the Moulouya River and (2) east of the Moulouya River to Algeria and Tunisia ( Beddek et al. 2018; Kindler et al. 2018). This pattern has been described for many biota, among them scorpions ( Buthus : Sousa et al. 2012), salamanders ( Pleurodeles : Carranza & Arnold 2004; Veith et al. 2004; Salamandra : Merabet et al. 2016), frogs ( Hyla : Dufresnes et al. 2019; Pelophylax : Nicolas et al. 2015; Dufresnes et al. 2024), freshwater turtles ( Emys : Stuckas et al. 2014), lizards ( Ptyodactylus : Metallinou et al. 2015; Timon : Paulo et al. 2008), snakes ( Daboia : Martínez-Freiría et al. 2017; Malpolon : Carranza et al. 2006; Natrix maura : Guicking et al. 2008), and rodents ( Meriones : Lalis et al. 2016).

Distribution and habitat. The geographical and altitudinal distribution of N. a. soumiafahdae subsp. nov. is determined by humidity and the presence of water bodies. The habitats can be streams, rivers, permanent ponds, and small lagoons or lakes ( Fig. 11 View FIGURE 11 ), including water reservoirs with dams. The distribution range is fragmented and resembles that of Emys orbicularis occidentalis in Morocco ( Bons & Geniez 1996; Velo-Antón et al. 2015). The range of N. a. soumiafahdae subsp. nov. includes disjunct occurrences in the Rif Mountains, the Middle Atlas, and a few records on the Atlantic plains (see Appendix 2 for a list of localities). The southernmost records reach the northern foothills of the High Atlas ( Fig. 3 View FIGURE 3 ). Most of the records are near rivers, streams, lagoons and other water bodies close to habitats with well-preserved old forests with Quercus pyrenaica , Cedrus atlantica , and Pinus pinaster as dominant tree species, but some sites are also near crop fields (Fahd 2001). Most records are in areas with high seasonal precipitation, and range from sea level to 1,960 m elevation at the Tanout ou Filal pass (Martínez del Mármol et al. 2019). In the Middle Atlas, most records are near Ifrane and Azrou; N. a. soumiafahdae subsp. nov. was also recorded near Oulmès. It has been recently recorded in the Jbel Tazzeka ( Kindler et al. 2018). In the Rif Mountains, it was recorded at Tamorot (Beni Halet) by Galán (1931), and subsequent research increased the number of sightings for these mountains ( Fahd & Pleguezuelos 1992, 2001; Mediani et al. 2015), suggesting that the Rif Mountains are currently the stronghold for grass snakes in Morocco.

Food spectrum. Bons (1967) mentioned for the Middle Atlas the anurans Discoglossus scovazzi and Pelophylax saharicus , and for Oulmès, the skink “ Chalcides chalcides ” as prey for Moroccan grass snakes. We wonder whether the latter food item is due to a confusion with a Malpolon monspessulanus , a typical skink eater, whereas there are not any other records of grass snakes eating skinks in the literature ( Braña 1998; Pleguezuelos 2018). Unicolored aged N. astreptophora are sometimes confused with M. monspessulanus , even by herpetologists or naturalists ( López Seoane 1884), so that any non-vouchered identification should be treated with caution. Martínez del Mármol et al. (2019: fig. 714) figured an adult N. a. soumiafahdae subsp. nov. trying to swallow an adult Berber toad Sclerophrys mauritanica , suggesting that large individuals prey on big bufonids, as known for other grass snakes ( Madsen 1983; Kabisch 1999).

Defensive behavior. When Natrix astreptophora soumiafahdae subsp. nov. cannot escape, they triangle the head and make puffing noises, or are feigning death, with open mouth, as known from other grass snake taxa ( Kabisch 1999; Pokrant et al. 2017). A death feigning individual from Chefchaouen with open mouth is figured in Martínez del Mármol et al. (2019: fig. 715). Also, a bad-smelling liquid can be secreted from the cloaca. There are no reports of autohemorrhaging in this taxon, a behavior reported for N. natrix sensu stricto ( Gregory et al. 2007; İğci et al. 2017) and N. helvetica ( Amat et al. 2024) , and very rarely for N. a. astreptophora (only reported in one specimen from Huesca, northeastern Spain; E. Ruiz Ara pers. comm.). Also, the ‘cobra stance’, known from European N. a. astreptophora ( Pokrant et al. 2017) , has not yet been described for Moroccan populations.

Reproduction. Fahd (2001) reported that a male with SVL of 38 cm had a great testicular volume, and two females of SVL 67 cm and 107 cm contained 11 and 28 eggs, respectively. This is in line with Bons (1967), who indicated for Moroccan populations clutch sizes of 10– 50 eggs.

Conservation status. In the European distribution range, Natrix astreptophora is widespread and in some regions abundant. However, in North Africa the species is generally rare, with a fragmented relict distribution ( Bons & Geniez 1996; Schleich et al. 1996; Martínez del Mármol et al. 2019; Fig. 3 View FIGURE 3 ). The number of historical and recent observations is low (e.g., Bons & Geniez 1996; Kalboussi & Achour 2018). Starting with Gervais (1848) and the general mention of the species for Algeria by Guichenot (1850), we traced a total of only 27 records for Tunisia and Algeria (excluding the questionable localities Gafsa and “Südalgier”) and 55 records for Morocco (Appendix 2), confirming the rarity of this snake species in the Maghreb.

The new subspecies Natrix astreptophora soumiafahdae subsp. nov. is distributed allopatrically and endemic to northwestern Morocco ( Fig. 3 View FIGURE 3 ). It is largely confined to montane areas in temperate habitats characterized by high humidity and dense plant cover, usually near streams, ponds, and lakes ( Fahd & Pleguezuelos 1992, 2001; Martínez del Mármol et al. 2019; Fig. 11 View FIGURE 11 ), with a few isolated records from the Atlantic plains ( Fig. 3 View FIGURE 3 ), remarkably in the same region from where also European pond turtles ( Emys orbicularis occidentalis ), another taxon with a relict distribution in the Maghreb, have been recorded in the past ( Bons & Geniez 1996). Apart from the Rif Mountains, where several populations were found ( Fahd & Pleguezuelos 2001; Mediani et al. 2015), records from other regions are scattered and scarce, despite targeted searches by experienced herpetologists, including us. Fahd & Pleguezuelos (2001) characterized Moroccan grass snakes to be very rare compared to the congeneric viperine snake N. maura (which might be a strong competitor) and as belonging to the rarest reptiles of Morocco.

Due to its strong genetic differentiation from both N. a. astreptophora and N. a. algerica, its relict distribution, and exceptional rarity N. a. soumiafahdae subsp. nov. should be considered as an evolutionarily significant conservation unit that deserves strict protection, continued research to improve the knowledge about its current distribution, and proactive conservation measures (especially prevention of habitat destruction and degradation) to ensure its long-term survival.