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Psammophis schokari (FORSKAL, 1775)

Photo thanks to David Oudjani

     
Identification "The anal is paired. The ventrals number 162 to 195, the subcaudals
93 to 149 pairs and the dorsals 17 to 19 in the row. The limit of recorded
length is 1210 mm."(Corkill 1935)

"Long, thin snake with a fl at head. Eyes are relatively large with a rounded pupil. Eight to ten upper labials, 5th and 6th entering the eye. Rostral broader than deep, visible from above. Nostril between two or three shields; internasals much shorter than the prefrontals. Frontal twice to two and a half as long as broad, about half as broad, in the middle, as the supocular, as long as or a little longer than its distance from the end of the snout, as long as the parietals. Loreal three to four times as long as deep. One PO (rarely divided), in contact with the frontal; two (rarely three) PtO. Temporals 2 + 2 or 3 (rarely 1 + 2). Nine (rarely eight or ten) UL, 3rd or 4th deepest, usually 3rd, 4th and 5th in contact with the preocular, 5th and 6th (rarely 4th and 5th or 6th and 7th) entering the eye. Five or six LL in contact with the anterior chinshields, which are shorter than the posterior (Fig. 78). One elongated loreal, three to four times as long as wide. Scale rows 17, VS 162 – 194 (160 – 173 in males and 162 – 180 in females), CS 95 – 149 (106 – 121 in males and 104 – 116 in females). Anal divided. Maximum length may reach 150 cm." (Amr and Disi 2011)

Derivatio nominis Brandstätter refers to Corkill & Cochrane (1966) who derive the name schokari from the Arabic 'shigari', which would mean 'from the trees'.
Common Names

Schokari Sand Racer, Sandrennatter, Schlanke Sandrennatter, Gröszaugige Sandrenn-Natter, Forskål’s Sand Snake, Schokari Sand Snake, Afro-Asian Sand Snake.
The latter names are accurate, as the eyes indeed seem large in relation to the oblong head, and the animal in comparison with P. sibilans is considerably slimmer built.

Also:
Variable sand snake, Afro-Asian sand snake, Sind sand snake, Tree snake, Forskal's sand snake, Serpent des sables.
Synonym Coluber schokari FORSKAL 1775
Coluber lacrymans REUSS 1834
Psammophis moniliger — DUMÉRIL & BIBRON 1854: 891
Psammophis punctatus DUMÉRIL & BIBRON 1854: 896
Psammophis sindanus STOLICZKA 1872 (fide SMITH 1943)
Psammophis schokari BOULENGER 1896: 157
Psamophis schokari [sic] — SCHMIDT 1939
Psammophis schokari — SMITH 1943: 363
Psammophis schokari — HAAS 1957: 81
Psammophis schokari — LEVITON 1959: 457
Psammophis schokari — FRYNTA et al. 1997
Psammophis schokari — SCHLEICH, KÄSTLE & KABISCH 1996: 515
Psammophis schokari — SCHMIDT & KUNZ 2005  
 

Known distribution of Psammophis schokari (shading) including sample sizes of specimens from each country used in the study of Cottone and Bauer 2009 (distribution source: Brandstätter, 1996).

Distribution NW India (Rajasthan, Punjab, Kashmir), Afghanistan (LEVITON 1959: 461), Pakistan, S Turkmenistan, Western Sahara ? Morocco, Algeria, Libya, Egypt, Sinai, Israel, Mali, Niger, Benin, Mauritania, Nigeria, Sudan, Ethiopia, Eritrea, Somalia, Saudi Arabia, Oman, United Arab Emirates (UAE), Kuwait, Syria, Jordan, Iraq, Iran (Kavir desert), Yemen

Type locality: Yemen  

Habitat:

Typically arid semi-desert. The presence of bushes and shrubs is important. In Egypt these animals streak from bush to bush in the heat of the afternoon. In real deep desert it does not penetrate. Sand dunes are in Egypt a typical element of the habitat.
"TheSchokari sand racer occurs in well-vegetated areas, including cultivated areas, among trees and shrubs, as well as in areas of sand and gravel where low shrubs and grasses occur. It can be found from sea-level to high-altitude mountainous regions" (Hellyer, P. and Aspinall, S. 2005)

Less expected: a swimming schokari.

Müller 1994: Disi a.o. (1988) indicate that P. schokari inhabits in many areas habitats that do not seem to correspond with their known preference of desert areas. This was confirmed by his observance of a dead P. schokari in Jordania in a valley with relatively dense vegetation and amply watered, which remembered of a dry mediterranean habitat. He found an overridden animal on a road that divided an arid and a more moist area, and he concluded that the animal would have visited the moist area at least once. Strictly taken, this could be not true, because the snake could just have used the hot road surface to warm up.

Kenmerken/
characteristics
This is one of the oldest known species of the genus, and the most studied. Nevertheless the taxonomic confusion has been rather great. In Egypt P. schokari and P. sibilans are sympatric, and it was questioned whether they are different morphological varieties or different species. Marx (1958) studied museum sepcimens with well documented origin. His conclusion was that these two species are distinguished in the following ways.
The number of ventrals and subcaudals in P. schokari is statistically rather larger than in P. sibilans, which corresponds to what is clear on superficial examnination: P. sibilans is a stouter bodied than P. schokari, which is more slender build with a more slender head, giving it a longer impression.

The colour pattern is also different. P. sibilans is characterized by a clearly visible vertical striping of the cheek portion, by a thin light striping along the middle of the dorsum, a broad dark lateral line on the first three scale rows and a yellowish belly. P. schokari has a thin dark line from the nose through the eye backwards, a dark longitudinal band over the ventral scales, and a thin broken striping at the edges of the ventral scales.

Psammophis (schokari) aegyptius is described by Marx in 1958 as a single species. Later authors did not follow his opinion, but considered it as a subspecies. Recently there is a return to the opinion of Marx. But Marx too admitted in 1958 that the correspondence between the species is very great, with an overlap of characteristics. For these characteristics, see P. aegyptius.

P. schokari occurs in Israel and the Sinai peninsula (Egypt) in three morphological forms not differing in scalation: (1) striped with four dark longitudinal stripes; (2) non-striped, non-marked or with a light dotted marking; and (3) striped on the hind part, overflowing to the front part. Each variety has a different and unique habitat within the studied area. Striped specimens are mainly found in the central, north and mediterranean coastal area, and not in the southern Negev or Sinai desert area. There we mainly find the non-striped specimens that do not occur in the north of Israel. In the intermediate area most of the snakes were caught that were half striped, half not-striped, as well as striped and non-striped specimens. These area's correspond with ecologicial differences.

"A physiological difference appears between the striped and non-striped snakes in skin resistance to water loss (Lahav & Dmi’el, 1996). Skin resistance to water loss is considered a reliable parameter for comparing different reptiles. Resistance to water loss was tested in two individuals of each of the two common morphs, at three body temperatures (25°C, 30°C, 34°C). At all three temperatures resistance was much higher in the non-striped morph, which in principle inhabits the more arid zone (Lahav & Dmi’el, 1996). Unfortunately it remains unknown whether these experimental animals had been collected in the allopatric or the sympatric parts of the morph distributions, precluding any systematic and evolutionary interpretation at this stage."(Kark, Warburg & Werner, 1997).

A study by Boaz Shacham (SCHACHAM 2004) is the first to report empirical evidence of polymorphism in P. schokari: both rear striped and fully striped hatchlings (in a 50:50 ratio) were born from a clutch laid by a single female; he found no evidence of sibling species within this taxon in
Israel and suggests considering the classification of the non-striped morph as a very light variant of the rear-striped (at least within Israel).

Brandstätter (1995) quotes Llabador (1947) who describes an almost black mutation from Algeria that he calls P. schokari var. nigra.

Reproduction: oviparous

Pictures: see the photographic index.

Psammophis aegyptius Marx, 1958, was formerly considered as a subspecies of Psammophis schokari but is currently recognized as a distinct species (Schleich et al. 1996). In Morocco/Western Sahara, three distinct morphotypes have been recorded for P. schokari: the striped form that occurs in the Atlantic Coast and occasionally in the High Atlas Mountains; the unicoloured form typically present in the High Atlas; and the Western-Sahara form with a slightly less slender body, weakly striped pattern and greyish belly (Bons & Geniez 1996). The First two co-occur in Southern and Central Morocco, while the Western-Sahara morph is the only form in this region. The occurence of striped and unicoloured morphotypes has also been recorded in Israel and Sinai, Egypt (Kark et al. 1997).

Rato et. al (2007) compared the genetic diversity between these three different morphotypes using mtDNA sequence data from North African specimens. They conclude that Psammophis aegyptius is the sister-taxon of Psammophis schokari,and since the level of genetic divergence between these two taxa (10.7%) is similar to that between the other species, these results are not in conflict with the recognition of Psammophis aegyptius as a distinct species. Within P. schokari four genetic lineages (Morocco/Western Sahara, Mauritania, Israel and Algeria) can be identified that are geographically coherent. The lineages from Morocco/Western Sahara and Mauritania are sister taxa, while the samples from Algeria form the basal split within the species. Thus the geographically close Moroccan and Algerian lineages are genetically the most divergent.

All three morphotypes from Morocco/Western Sahara are closely related and part of the same Moroccan clade. This indicates that colour patterns in Psammophis schokari do not reflect phylogenetic divergence.

Kark et al. (1997) reached the same conclusions regarding the striped and unicoloured morphotypes in Israel. This colour polymorphism is therefore probably an ecological adaptation to the environment. The striped morph may be advantageous in a more densely covered vegetation zone, where it is mainly found, whereas the unicoloured morph may be more cryptic in the more open Saharo-Sindian desert vegetation habitat.

Climate changes in, with humid periods alternating with arid ones, are probably the cause of the genetic divergence between the geographically adjacent populations of Algeria and Morocco/Western Sahara.

 

Descriptions Wall 1911:

Psammophis schokari. (Forskal).
Several specimens from Quetta, Toba, Marachak, Jhalawan, Kishingi, Chaman and Khost. The specimen from Khost is exactly like specimens of condanarus in colouration, there being a median and two lateral narrow stripes of buff, the median involving the vertebral row only, and the lateral the contiguous halves of the 3rd and 4th rows above the ventrals. The specimen from Marachak is very similar, but the buff stripes are broader, the median involving the vertebral, and half the adjacent rows, and the lateral invol- ves the 4th and half the 3rd and 5th rows. The striping is not so well defined and conspicuous as in the previous specimen. The rest have a dark vertebral stripe involving the vertebral, and the adjacent half rows, and there is a series of blackish narrow apical stripes on the scales of the 6th row. There are no light stripes at all anteriorly, but the buff stripes typical of condanarus are obscurely indicated posteriorly. It seems to me very dubious whether all these specimens should be considered schohari, I incline to the opinion that there may be two species judging from the peculiarities of the subcaudals, the supralabials, and the number of scales in the posterior part of the body as will be seen from the annexed tabulated details.

Video

Three captive specimens from Egypt. 

 

Pictures

P. schokari swallowed a lizard, picture by Abdellah Bouazza (https://www.facebook.com/abdellahbiho?fref=photo)

Picture by David Oudjani. Schokari racer swallowing an Arabian lizard snake.

Picture by David Oudjani. Schokari racer swallowing an Arabian lizard snake.

Habitat, picture by David Oudjani

Habitat, Picture by David Oudjani

Picture by David Oudjani

Picture by David Oudjani

Picture by David Oudjani

 

Food In the study of Cottone and Bauer (2009) 79% of the extracted contents of the stomach consisted of mainly terrestrial lizards and scincids, with variable temperal activity patterns. Larger P. schokari tended to switch to endothermic vertebrates.

As for its venom: a three weeks old small mouse, when caught by the head, is motionless within a minute.

In Libya "The Schokari sand racer occurs in well-vegetated areas, including cultivated areas, among trees and shrubs, as well as in areas of sand and gravel where low shrubs and grasses occur. It can be found from sea-level to high-altitude mountainous regions.
An agile and active daytime predator, when chasing prey it is capable of reaching speeds of up to 16 kilometres per hour, and can even climb trees in order to reach adult birds and nestlings.
Prey includes lizards, small birds, rodents and other snakes, which are captured with a swift bite followed by a chewing motion to deliver the snake’s venom. Once immobilised, the prey is swallowed head first.
Despite being a venomous species, the Schokari sand racer is not dangerous to humans, and in response to threats its main form of defence is to use its speed to escape."
(Rentokil Libya, website, pest control guide)
Breeding P. schokari displays no sexual dimorphisme in body size and shape, though males tend to have larger mean body traits. This is similar to almost all of the psammophiids. 
Males and females exhibit their highest levels of sexual activity in synchrony and exhibit prenuptial spermiogenesis and a Type 1 vitellogenic cycle,  respectively.
Mating occurs at the end of the rainy season. These findings from a Northern Hemisphere temperate sand snake are consistent with previous results for both tropical and south temperate Psammophis.

Clutch size is always 10 or less (average 7.3).
See: Cottone en Bauer 2009.

"The Schokari sand racer mates during the rainy season, between April and June. The female lays a small clutch, usually of six to ten eggs. The males reach sexual maturity at slightly a smaller size than the female." (Rentokil Libya)

References
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    Kark, Salit, Ittai Warburg & Yehudah L. Werner. Polymorphism in the snake Psammophis schokari on both sides of the desert edge in Israel and Sinai. Journal of Arid Environments (1997) 37: 513–527
  • Trape, J.-F. & Mane, Y. 2006. Guide des serpents d’Afrique occidentale. Savane et désert. [Senegal, Gambia, Mauritania, Mali, Burkina Faso, Niger]. IRD Editions, Paris, 226 pp.
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Sources

Pictures

Pictures of the infertile eggs in 2015:

 

Slide from 1990: adult striped specimen from Egypt Egg, laid by a wild caught female in 1990
Hatching egg in 1990: a twin! Bad slide, but still...
One of the hatchlings in 1990 One of the hatchlings in 1990
One of the hatchlings in 1990    
 

Pictures by David Oudjani