Oligodon sublineatus Dumeril , Bibron & Dumeril , 1854

Amarasinghe, A. A. Thasun, Karunarathna, D. M. S. Suranjan, Campbell, Patrick D. & Ineich, Ivan, 2015, Systematics and ecology of Oligodonsublineatus Dumeril, Bibron & Dumeril, 1854, an endemic snake of Sri Lanka, including the designation of a lectotype, Zoosystematics and Evolution 91 (1), pp. 71-80 : 71

Taxon classification Animalia Squamata Colubridae

Oligodon sublineatus Dumeril, Bibron & Dumeril, 1854 Figs 1, 2, 3; Tables 1, 2

Remarks.

Standard morphometric and meristic data of the two syntypes are presented in Table 1. We hereby recognise two syntypes: the larger specimen (MNHN 3238) and the smaller specimen (MNHN 3239). Uncertainties still exist in Oligodon taxonomy and Oligodon sublineatus may represent a cryptic species complex in Sri Lanka (see table 2 showing the wide range of subcaudal and ventral counts within Oligodon sublineatus ), therefore it is necessary to stabilize the name with a recognised lectotype. There are two main reasons for selecting MNHN 3238 as the lectotype: (1) it was used in the original description and its morphometric data has been provided and (2) it is a fully grown, well-developed and well preserved adult specimen in good shape.

Lectotype

(here designated). MNHN 3238, adult female collected from the Philippines (mistakenly so in the original description) [from Java (also in error) according to the museum registry] by an unknown collector [by Bosc (in error) according to the museum registry].

Paralectotype.

MNHN 3239, sub adult male collected at ‘Ceylan’ [= Sri Lanka] by Leschenault. This specimen was previously erroneously considered as the holotype by Wallach et al. (2014).

Diagnosis.

Oligodon sublineatus shows sexual dimorphism in scalation (Table 2) and is distinguished from all congeners by the following characters: SVL 152-310 mm; TAL 20.0-42.0 mm; 130-161 ventrals; 23-42 subcaudals (divided); anal plate divided; loreal present; seven supralabials; temporals 1+2; ventral side with three series of dark brown points forming almost continuous stripes, with the middle series of points absent on the tail; dorsal coloration (live or in alcohol) greyish brown, speckled with small elongated spots irregularly placed; posterior part of the jaws has a large, oblique spot extending along the neck posteriorly; dorsally a “˄” shaped marking between the eyes, which continues laterally across them; an irregular, brown, transversal band from the frontal to the post-parietal region.

English translation of the original French description in Duméril, Bibron & Duméril ( 1854: 57).

Characters. Ventral side with three series of points forming stripes.

This species is mostly characteristic, as its specific name, by having three black stripes along the ventral side, which are made up of a series of points, meeting together. The two stripes outside the ventral plates form a continuous line up to the ventral surface of the tail, but the central one is made up of distinct points in the centre of the ventral plates. These points are quite large, round and wide posteriorly, and are as notched at the front; the median stripe does not prolongate onto the ventral side of the tail.

Dorsal coloration grey, speckled with lines or with small elongated spots irregularly placed; however, around the anterior third of the body and laterally, three of those spots appear enlarged with increased width, having a circular border. The spots are constricted centrally and have white borders. The posterior section of the jaws has a large, oblique patch along the neck posteriorly where it forms a tip pointing in the opposite direction to the characteristic collar of the first species [note from the translator: Oligodon sub-quadratum ].

Dorsal scales are very smooth, and are close to each other; they are slightly overlapping, like roof tiles, mostly around the tail area, and in this respect, very skink-like in appearance.

Rostral plate is notched, and crescent shaped; other plates covering the head are large and clearly distinct as in colubrids.

We were only able to examine one well preserved specimen, having no clues as to the origin of the specimen [the Philippines] and the name ' Oligodon torquatus ' appears along with the letter “R” on the jar.

Another specimen, younger and obviously added much later, had a median stripe made up of numerous spots which were less distinct, was collected from Ceylan by Mr. Leschenault. This specimen bears all the characters previously described: the large, brown, post-maxillary mark set posteriorly on the neck forming a croissant shape; with a laterally set, black mark extending onto the anterior third of the body.

We counted 15 scale rows on that specimen, 155 ventrals and 25 subcaudals.

Total length was 180 cm [sic]; among them 155 for SVL and 25 for the tail.

Description of the designated lectotype, MNHN 3238.

Adult female, SVL 254 mm; tail length 35 mm; head elongate (HL 4.3% of SVL), twice as long as wide (HW 43.5% of HL), slightly flattened, distinct from neck; snout elongate (ES 31.5% of HL), moderate, blunt in dorsal view, rounded in lateral profile, forming an oval shape, rather depressed.

Rostral shield large, hemispherical, distinctly visible from above, pointed posteriorly; interorbital width broad (IO 78.7% of HW); internasals semicircular; nostrils rather large; nasals completely divided by nostrils into two scales unequal in size; anterior nasal larger, in anterior contact with rostral, internasal dorsally, 1st SUP ventrally; posterior nasal in contact with internasal and prefrontal dorsally, loreal posteriorly, 1st and 2nd SUP ventrally; prefrontal rather large, broader than long, and subhexagonal; frontal large, subhexagonal, elongate posteriorly and longer than its width; supraoculars narrow, elongated, subrectangular, posteriorly wider; parietals large, butterfly wing-like in shape, bordered by supraoculars, frontal, upper postoculars anteriorly, anterior and upper posterior temporals, and six dorso-nuchal scales posteriorly; loreal large, slightly elongated, subrectangular, in contact with prefrontal dorsally and preoculars posteriorly, ventrally only touching the 2nd SUP; one preocular (both sides), vertically elongated, subrectangular, in contact with prefrontal and loreal anteriorly, supraocular dorsally, and 3rd SUP ventrally; eye moderate (ED 15.7% of HL), elliptical, nearly a half of the size of snout length (ED 50% of ES), pupil rounded; two postoculars, upper postocular smaller, quadrangular, contact with supraocular and parietal broad, in narrow contact with anterior temporal; lower postocular crescent in contact with 4th and 5th SUP ventrally, anterior temporal posteriorly; temporals 1+2, elongated, hexagonal; anterior temporal larger and longer than posterior temporals, in contact with parietal dorsally, 5th and 6th SUP ventrally; posterior temporals smaller, lower one in contact with 6th and 7th supralabials ventrally.

Supralabials 7 (on both sides), 4 th– 7th larger in size; 1st SUP in contact with rostral anteriorly, nasals dorsally, 2nd supralabial with posterior nasal and loreal dorsally, 3rd SUP with preocular and orbit dorsally, 4th SUP with orbit and the lower postocular dorsally, 5th SUP with lower postocular and anterior temporal dorsally, 6th supralabial with anterior temporal and lower posterior temporal dorsally, and 7th SUP with lower posterior temporal dorsally and body scales posteriorly.

Mental of moderate size, triangular; first infralabial pair larger than mental plate and in broad contact with each other, in contact with anterior chin shield posteriorly; eight infralabials, 1 st– 5th in contact with first chin shield, 5th infralabial largest in size in narrow contact with the anterior chin shield and in broader contact with the posterior chin shield; 6 th– 8th infralabials in contact with gular scales; two larger anterior chin shields, and two smaller posterior chinshields all in broad contact; posterior chin shield bordered posteriorly by six gular scales.

Body robust, elongate and sub cylindrical; costal scales in 17-15-15 rows, all smooth and bluntly pointed; 150 ventral scales; anal plate divided. Tail comparatively short (TL 13.8% of SVL), robust and thick; subcaudals 28, divided.

Description of the paralectotype, MNHN 3239, and an additional specimen, NMSL 5161.

The values of NMSL 5161 (when different) included within parenthesis. Sub adult male (adult male), SVL 150.0 (183.3) mm; head elongate, HL 5.4 (5.6)% of SVL, twice as long as wide, HW 50.6 (53.9)% of HL, slightly flattened, distinct from neck; snout elongate, ES 31.4 (33.3)% of HL, moderate, blunt in dorsal view, rounded in lateral profile, forming an oval shape, rather depressed.

Rostral shield large, hemispherical, distinctly visible from above, pointed posteriorly; interorbital width broader, IO 80.5% of HW; internasals semicircular; nostrils rather large; nasals divided into two scales unequal in size; anterior nasal larger, in contact with the rostral plate anteriorly, internasal dorsally, 1st SUP ventrally; posterior nasal in contact with internasal and prefrontal dorsally, loreal posteriorly, 1st and 2nd SUP ventrally; prefrontal rather large, broad, and subhexagonal; frontal large, subhexagonal, elongate posteriorly and longer than its width; supraoculars narrow, elongated, subrectangular, posteriorly wider; parietals large, butterfly-like in shape, bordered by supraoculars, frontal, upper postoculars anteriorly, anterior and upper posterior temporals, and six dorso-nuchal scales posteriorly; loreal large, slightly elongated, subrectangular, in contact with prefrontal dorsally, preoculars posteriorly, posterior nasal anteriorly, ventrally just meets the 2nd SUP; one preocular in both sides, vertically elongated, subrectangular, in contact with prefrontal and loreal anteriorly, supraocular dorsally, and 3rd SUP ventrally; eye moderate, ED 17.3 (17.6)% of HL, elliptical, nearly a quarter of the snout length, ED 51.9 (56.2)% of ES, pupil rounded; two postoculars, upper postocular smaller, quadrangular, in contact with supraocular and parietal broad, in narrow contact with anterior temporal; lower postocular crescent in contact with 4th and 5th SUP ventrally, anterior temporal posteriorly; temporals 1+2, elongated, hexagonal; anterior temporal larger and longer than posterior temporals, in contact with parietal dorsally, 5th and 6th SUP ventrally; posterior temporals smaller, lower one in contact with 6th and 7th SUP ventrally.

Supralabials 7 on both sides, 4 th– 7th larger in size; 1st SUP in contact with rostral anteriorly, nasals dorsally, 2nd SUP with posterior nasal and loreal dorsally, 3rd SUP with preocular and orbit dorsally, 4th SUP with orbit and the lower postocular dorsally, 5th SUP with lower postocular and anterior temporal dorsally, 6th SUP with anterior temporal and lower posterior temporal, and 7th SUP with lower posterior temporal dorsally and body scales posteriorly.

Mental moderate, triangular; first infralabial pair larger than mental and contact with each other broad, in contact with anterior chin shield posteriorly; eight infralabials, 1 st– 5th in contact with first chin shield, 5th infralabial largest in size in narrow contact with anterior chin shield and contact with posterior chin shield broad; 6 th– 8th infralabials in contact with gular scales; two larger anterior chin shields, and two smaller posterior chinshields all in broad contact; posterior chin shield bordered posteriorly by six gular scales.

Body robust, elongate and sub cylindrical; costal scales in 17-15-15 rows, all smooth and bluntly pointed; 138 (142) ventral scales; anal plate divided. NMSL 5161 has an everted hemipenis covered by lobes, non-bifurcated, slightly clavate; base naked; sulcus spermaticus single and deep; spinous ornamentation present on each lobe, shorter spines at the apex; apex not divided into segments (Fig. 2E); tail comparatively short, TL 18.0 (20.5)% of SVL, robust and thick; subcaudals 36 in both specimens, divided.

Distribution.

This species has never been recorded outside of Sri Lanka, hence we here restrict terra-typica to Sri Lanka. Wall (1921), Smith (1943), Deraniyagala (1955), De Silva (1980), de Silva (1990), Das and de Silva (2005), Somaweera (2006), Karunarathna and Amarasinghe (2010, 2011, 2012), Botejue and Wattavidanage (2012), and Karunarathna et al. (2010, 2013) recorded this species from Bellanwila–Attidiya, Beraliya, Colombo, Galle, Gammaduwa (Knuckles), Kitulgala, Kotmale, Kukulugala, Matugama, Nilgala, Peradeniya, Ratnapura, Veyangoda, Welimada, and Yatiyantota (Fig. 3). In addition to the above locations, during our fieldwork operations of the last decade we have recorded (not collected) Oligodon sublineatus from a 10-1600 m altitude range, including all vegetational zones of Sri Lanka: Ambalangoda (6°14 ’42.35’’ N, 80°03 ’44.56’’ E), Anuradhapura (8°20 ’46.43’’ N, 80°25 ’43.77’’ E), Atweltota (6°31 ’33.87’’ N, 80°18 ’12.02’’ E), Baduraliya (6°30 ’53.70’’ N, 80°13 ’41.81’’ E), Bibile (7°10 ’58.02’’ N, 81°13 ’43.61’’ E), Chilaw (7°35 ’11.49’’ N, 79°49 ’16.54’’ E), Deniyaya (6°20 ’11.54’’ N, 80°34 ’10.44’’ E), Elpitiya (6°17 ’39.31’’ N, 80°08 ’44.78’’ E), Eluwankulama (6°20 ’11.54’’ N, 80°34 ’10.44’’ E), Gampaha (7°05 ’03.68’’ N, 79°58 ’25.66’’ E), Habarana (8°11 ’12.43’’ N, 80°50 ’17.89’’ E), Horana (6°42 ’24.74’’ N, 80°03 ’02.77’’ E), Illukkumbura (Knuckles) (7°35 ’46.09’’ N, 80°46 ’14.10’’ E), Kalutara (6°35 ’13.29’’ N, 80°58 ’21.49’’ E), Kanneliya (6°12 ’37.49’’ N, 80°24 ’04.60’’ E), Kegalle (7°14 ’10.26’’ N, 80°19 ’57.27’’ E), Kottawa-Homagama (6°47 ’07.00’’ N, 79°57 ’52.17’’ E), Kurunegala (7°30 ’25.80’’ N, 80°23 ’46.95’’ E), Kuruwita (6°46 ’29.02’’ N, 80°22 ’35.50’’ E), Maharagama (6°50 ’52.54’’ N, 79°55 ’45.54’’ E), Mahiyanganaya (7°20 ’06.03’’ N, 81°00 ’34.51’’ E), Matara (5°57 ’08.63’’ N, 80°31 ’59.74’’ E), Monaragala (6°52 ’40.25’’ N, 80°20 ’27.39’’ E), Naula (7°44 ’18.42’’ N, 80°43 ’38.22’’ E), Nugegoda (6°51 ’35.26’’ N, 79°53 ’08.19’’ E), Panadura (6°42 ’42.76’’ N, 79°54 ’24.44’’ E), Pidurutalagala (7°01 ’08.11’’ N, 80°47 ’23.47’’ E), Polonnaruwa (7°56 ’15.64’’ N, 81°01 ’15.38’’ E), Puttalam (8°02 ’42.88’’ N, 79°51 ’38.84’’ E), Rakwana (6°28 ’03.23’’ N, 80°36 ’32.84’’ E), Ritigala (8°12 ’35.71’’ N, 80°35 ’02.78’’ E), Sinharaja (6°24 ’59.18’’ N, 80°24 ’28.33’’ E), Tanamalwila (6°27 ’00.66’’ N, 81°09 ’07.66’’ E), Tissamaharamaya (6°16 ’52.45’’ N, 81°16 ’41.40’’ E), Trincomalee (8°35 ’57.38’’ N, 81°10 ’15.73’’ E), Udawalawe (6°26 ’48.46’’ N, 80°52 ’26.25’’ E), Wasgomuwa (7°43 ’23.36’’ N, 80°58 ’06.01’’ E), Wilpattu (8°30 ’51.13’’ N, 79°57 ’44.67’’ E), Yagirala (6°22 ’47.13’’ N, 80°10 ’23.93’’ E) (see Fig. 3 for the distribution map).

The result of the application of the IUCN (2013) B2 a, b (iii) Red List criteria shows that Oligodon sublineatus as Least Concern (LC): recorded from an altitude range of 10-1600 m in all vegetation zones of Sri Lanka. Its area of occupancy is 6,000 km2, and its extent of occurrence is 40,000 km2.

Natural history.

A nocturnal snake, sometimes active during day time. Temperature, humidity, and light intensities for daytime activity were respectively measured at 24.8-27.2 °C, 67-82%, and 38-365 lux, based on 50 observations in dense forested areas. It usually does not bite, but if this does occur then it will lead to soreness, pain and temporary bleeding in the victim. Biting has been occasionally observed during touching or handling attempts by the victim. When frightened, the snake either coils up and hides its head within its coiled up body; or it quickly tries to escape to a safe hiding place inside the leaf litter. When the snake coils, it enlarges its body and displays its vivid skin colours (white, pink and brown), which is visible between the scales around the mid body. We observed, on a number of occasions, the snake practicing thanatosis (death mimicry) for up to 10-15 minutes after carrying out our own handling attempts. Once the snake had noticed that threat had disappeared, it quickly escaped and hid itself in the leaf litter. We have observed this species living in sympatry with other snakes of several families such as Aspidura guentheri Ferguson, 1876 ( Natricidae ); Hypnale zara (Gray, 1849) ( Viperidae ); and Sibynophis subpunctatus ( Duméril, Bibron & Duméril, 1854) ( Colubridae ).

Based on our observations, its diet consists mostly of lizards (saurophagy) and small snakes eggs (oophagy), small spiders, beetles, other insects and the larvae of other invertebrates. More specifically, we observed the snake feeding on ground dwelling skinks ( Lankascincus sp.) and geckos ( Hemidactylus frenatus and Cnemaspis sp.). If the prey is large, the snake wraps itself around it and squeezes it until it suffocates. In captivity, it was fed with jumping spiders, small wild cockroaches, annelid worms, meal-worms, small frogs, and the freshly detached tail tips of geckos.

During the breeding season ( May–June) 3-5 individuals can be observed close by and we observed several copulations in the evenings just after dark (18.0-19.0 hrs). The species lays 3-5 eggs at a time on dry, cool, loose soil or under decaying logs on the ground (soil temperature 26.2-27.9 °C; humidity 58-73%; light intensity 0-27 lux, based on observations of 10 ovipositions). Eggs are cream in colour and oval in shape (12-14 mm long and 4-5 mm wide, n = 40). The lectotype MNHN 3238 is a gravid female with three eggs in its genital tract. The incubation period is 38-45 days (based on observations of 10 incubating clutches). We did not see the parents close by during the incubation nor shortly afterwards, indicating the lack of parental care of the eggs or hatchlings. The new born juveniles were 4-5 cm in total length and their body colour varied from dark brown to black. We noticed that ants were their main egg predators on about ten occasions. We also observed on several occasions, this snake attempting to avoid ant-nests when moving or resting.

We have found this species inside termite mounds on many occasions, an observation also made by Smith (1943). This may indicate either a strategy used by the snake to avoid ants (because we never observed ant nests in or around termite mounts) or a neat way for the snake to have instant access to food (may be feeding on termite eggs). Further studies on habitat ecology would be interesting. Even though this is a ground dwelling species, we observed it climbing on rock boulders which have crevices, indicating that this snake may be searching for geckos or their eggs for food. During floods, the snake is usually found off the floor, in trees at 1-2 m above ground level. It is also found deep inside forests, and has been observed under old coconut harnesses, decaying logs on the ground, and inside termite mounds (as mentioned earlier) set in well maintained home gardens.

Road kills are identified as a major growing threat in addition to forest fragmentation and habitat loss. People are also a threat, killing the snake out of fear, believing that it to be venomous, especially because as it displays such vivid head and body colours. We observed natural predators including birds: the yellow-billed babbler [ Turdoides affinis (Jerdon, 1845)], southern coucal ( Centropus parroti Stresemann, 1913), common mynah [ Acridotheres tristis (Linnaeus, 1766)], white-throated kingfisher [ Halcyon smyrnensis (Linnaeus, 1758)], and the Sri Lankan grey hornbill ( Ocyceros gingalensis Shaw, 1811); ophiophagous snakes including: two elapids, the Sri Lankan krait ( Bungarus ceylonicus Günther, 1864), and the Indian krait ( Bungarus caeruleus Schneider, 1801); and amphibians including forest toads ( Duttaphrynus sp.). In addition, Karunarathna and Asela (2007), and Karunarathna (2009) have observed the common rat snake ( Ptyas mucosus Linnaeus, 1758) feeding on Oligodon sublineatus and Oligodon calamarius (Linnaeus, 1758) in Sri Lanka