Toxicodryas blandingii (HALLOWELL, 1844)
Can you confirm these amateur observations of Toxicodryas blandingii?
|Higher Taxa||Colubridae, Colubrinae, Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata (snakes)|
|Common Names||E: Blandings Tree Snake|
|Synonym||Dipsas Blandingii HALLOWELL 1844: 170|
Triglyphodon fuscum DUMÉRIL & BIBRON 1854
Dipsas Fischeri JAN in DUMÉRIL 1859: 212
Triglyphodon fuscum var. obscurum DUMÉRIL 1861
Dipsas fasciatus FISCHER 1856 (fide HALLERMANN 1998: 202)
Disas valida FISCHER 1856: 87
Dipsas globiceps FISCHER 1856: 89
Toxicodryas blandingii — HALLOWELL 1857: 60
Dipsas regalis JAN 1871: 3
Dipsas globiceps var. tumboensis MÜLLER 1885: 688
Dipsadomorphus blandingii — WERNER 1899
Dipsadomorphus blandingii — STERNFELD 1917
Boiga blandingii — SCHMIDT 1923: 103
Boiga blandingii — MENZIES 1966
Boiga blandingii — PITMAN 1974
Boiga blandingi subfulva STUCKI-STIRN 1979: 381
Toxicodryas blandingii — MEIRTE 1992: 110
Toxicodryas blandingii — TRAPE & ROUX-ESTÈVE 1995: 40
Boiga blandingii — BROADLEY 1998
Toxicodryas blandingii — RÖDEL et al. 1999
Boiga blandingii — HUGHES 2000
Boiga blandingii — GOSSMANN et al. 2002
Toxycodryas [sic] blandingii — TRAPE & MANÉ 2002
Boiga blandingii — PAUWELS et al. 2004
Toxicodryas blandingii — TRAPE & MANÉ 2006
Toxicodryas blandingii — CHIRIO & LEBRETON 2007
Toxicodryas blandingii — ULLENBRUCH et al. 2010
Boiga blandingii — SEGNIAGBETO et al. 2012
Toxicodryas blandingii — WALLACH et al. 2014: 733
Boiga blandingii — CARLINO & PAUWELS 2015
Toxicodryas blandingii — SPAWLS et al. 2018: 511
Toxicodryas blandingii — GREENBAUM Et al. 2021
|Distribution||W Kenya, Uganda, Republic of South Sudan (RSS), Angola, Gabon, |
Cameroon, Equatorial Guinea, Central African Republic, Nigeria, Senegal, Guinea-Bissau, Gambia,
Benin, Togo, Ghana, Ivory Coast, Liberia, Sierra Leone, Guinea (Conakry), Democratic Republic of the Congo (Zaire), Congo (Brazzaville), Zambia
Type locality: "Liberia, West Africa."
|Types||Holotype: ANSP 10083 (fide Greenbaum et al. 2021, although reported as lost by previous authors), a 1670 mm specimen (Blanding) (fide V. Wallach, pers. comm.)|
|Diagnosis||Diagnosis. Toxicodryas blandingii, as recognized herein, is restricted to West Africa and west-central Africa (west of the confluence of the Congo and Ubangi rivers), defined by the following combination of characters: maximum SVL > 1 meter (vs. maximum SVL < 1 meter in T. pulverulenta and T. adamanteus sp. nov.); DSRN 23–25 (vs. 19–21 in T. pulverulenta and 18–23 in T. adamanteus sp. nov.); DSRM 21–25 (vs. 19–21 in T. pulverulenta and 18–21 in T. adamanteus sp. nov.); cloacal plate usually divided (vs. divided or undivided in T. vexator sp. nov., and always undivided in T. pulverulenta and T. adamanteus sp. nov.); adult males glossy or velvety black with a yellow venter, and adult females light brown, gray, or yellowish-brown with light-brown or cream cross-bars on the flanks, with yellowish-brown venters (vs. both sexes brown to pink with darker cross-bars that often enclose a whitish spot, and the dorsum and venter sprinkled with fine dark brown or black spots in T. pulverulenta and T. adamanteus sp. nov.); hemipenis relatively short and massive (i.e., broad), proximal third covered with spines, distal two-thirds dimpled with a flattened apex (vs. relatively long with long spines mid-way along the shaft that decrease in size towards the apex and base, and with a domed apex in T. pulverulenta and T. adamanteus sp. nov.); venom toxicity LD50 = 2.85–3.55 mg/kg in mice (vs. venom toxicity LD50 = 4.88 mg/kg in mice for T. vexator sp. nov.) (Greenbaum et al. 2021).|
Variation. Morphometric variation of Toxicodryas blandingii is shown in Table 1. Müller (1885:688) provided data for a snake from Ghana with 15 infralabials and noted that most of its scales have two “Endgruben” [terminal pits], which likely refer to apical pits. In his description of Dipsas globiceps var. tumboensis Müller (1885) noted his specimen from Guinea (Fig. 7) had 147 subcaudals. In snakes from West Africa (without separating by sex), Angel (1933) noted a temporal formula of 2 + 2 or 2 + 3, 21–25 scales at midbody, 240–289 ventrals, 120–147 subcaudals, either an undivided or divided cloacal plate, and a maximum total size of 2290 mm, and nearly verbatim variation was listed by Villiers (1950a), Doucet (1963), Stucki-Stirn (1979), Chippaux (2006), and Trape & Mané (2006). However, in snakes from Ghana, Swiecicki (1965:302) noted a maximum total length of 2450 mm for a “black form” individual, Gauduin (1970) listed the maximum total length as 2700 mm (600 mm tail) for Cameroon, Chirio & LeBreton (2007) provided a slightly larger total length of 2740 mm for Cameroon, and Luiselli et al. (1998a) noted a maximum size of 2800 mm, presumably for Nigeria. Villiers (1951) noted an unsexed individual from Benin with 115 subcaudals. Cansdale (1965) documented 21–25 scales at midbody, and Segniagbeto et al. (2011) documented snakes from Togo with 19–24 scales at midbody and 102–159 subcaudals.
In our examined specimens, temporal formula includes the variation noted by Angel (1933), but is more extensive (2 +5, 3 + 4, 3 + 3, 1 + 5, 3 + 2, or 2 + 4), and either supralabials 3–5 or 4–6 contact the eye, which is consistent with the observations of Angel (1933), Villiers (1950b), and Chippaux (2006); the latter author also noted that sometimes only 2 supralabials contact the eye. Rasmussen (1997a) noted specimens with the 4th–5th, 5th–7th, or 4th–7th supralabials in contact with the eye, and in general, this species has sloping and smooth scales with apical pits, and the vertebral row is greatly enlarged. The holotype, one male and one female from Liberia (Loveridge 1941; Johnsen 1962), one male from Gabon (Pauwels et al. 2002b), one male from DRC (RBINS 10888), and a juvenile from Cameroon (Werner 1897) are unusual in having an undivided cloacal plate, because all other examined specimens have a divided cloacal plate, including the type specimens of Dipsas fasciata, D. valida, and D. globiceps (Fischer 1856). Rasmussen (1997a) remarked that his specimens have either a divided or undivided cloacal plate. In his book on West and Central African snakes, including countries west of the Congo River, Chippaux (2006:154) noted the anal [cloacal plate] is sometimes entire, but more often divided. Trape & Mané (2006) stated that the cloacal plate is almost always divided. Segniagbeto et al. (2011) noted individuals with divided or undivided cloacal plates in Togo.
Combined descriptions by Fischer (1856) of the teeth of Dipsas fasciata, D. valida, and D. globiceps (all now synonyms of T. blandingii) suggest the species has 9 maxillary teeth that increase in size posteriorly, followed by two fangs (three on the right side in one specimen), and 12 mandibular teeth, which decrease in size posteriorly. In snakes from Ghana, Leeson (1950) noted 10–11 maxillary teeth, becoming larger posteriorly, and two fangs followed by a shorter fang; fourteen large palatine and pterygoid teeth, and 15 mandibular teeth (anterior ones largest). Taylor & Weyer (1958:1217) described a Liberian specimen with 9–10 maxillary teeth (on different sides) that increase in size from the 1st to 4th tooth, and then become subequal; two fangs occur after this series of teeth, and after a short diastema, there is a third fang with only traces of a groove. A second Liberian specimen had 10 maxillary teeth followed by three fangs, the last of which had only “a suggestion of a groove.” Based on specimens ranging from Guinea to Congo, Rasmussen (1997a:98) noted 10 maxillary teeth followed by three enlarged, furrowed venomous teeth, with the 3rd fang slightly smaller than the previous two.
Fischer (1856) provided detailed descriptions of the color patterns of West African Dipsas fasciata, D. valida, and D. globiceps (all now synonyms of T. blandingii), which seem to suggest he examined a subadult male that had been kept in alcohol for a long (unspecified amount) time (D. fasciata), an adult female (D. valida), and a subadult that retained juvenile coloration (D. globiceps). In his description of Dipsas globiceps var. tumboensis Müller (1885:689) noted his specimen from Guinea (Fig. 7) had a gray-reddish dorsum with 30 black transverse bands, usually containing milky white spots. The frontal, supraoculars, and occipital scales had large black spots, the labial scales and postoculars were edged with black, and the head shields had multiple milk-white speckles. The tail was bright red with dark, irregular transverse bands. Aspects of this coloration description are highly unusual for this species (e.g., bright red tail), and more typical of T. pulverulenta, but the black edging of the labial scales, number of preoculars (3), supralabials in contact with the eye (5 and 6), ventrals (269), and subcaudals (147) clearly indicate this taxon is a synonym of T. blandingii (Fig. 7, Tables 1–2).
Mocquard (1887:80) described a recently collected, unsexed subadult (“la longueur du tronc” [trunk length] 1.1 m) from Gabon as having a dorsal color of a general tint of Burgundy with slightly darker spots on the flanks that have a dirty white spot a little above their lower edge. Mertens (1938) described an adult male from Cameroon as solid black dorsally and ventrally, with the exception of the anterior third of the venter, which was white, but the ventral scales had dark gray edges. The labial scales were gray with vertical black borders. Villiers (1950b) described the color pattern of an unsexed individual from Ivory Coast as sooty black or brownish in places on the dorsum; underside iridescent dark gray posteriorly, becoming whitish anteriorly, with the posterior edge of the ventrals edged with gray; underside of head white, and labials whitish and edged in black. Another unsexed individual from Liberia was described as bluish black above, yellow below; supralabials yellow with black edges, and posterior part of venter and underside of tail black. A third unsexed individual from Liberia had identical coloration to the latter one, except for the presence of whitish bars on the neck. Leeson (1950) noted that snakes from Ghana have a dull green or gray dorsum. Monard (1951:162) described an unsexed individual from Cameroon as a beautiful light red-brown, “barré” [barred] with dark brown. Taylor & Weyer (1958:1217) described a Liberian brown-phase female with pale grayish green on the ventral side of the head and neck, merging into gray with “a greenish cast” 12.7 cm posteriorly, and at 40.6 cm behind the head, it transitioned into plain tan to the tip of the tail. Isemonger (1962:12) remarked that this species has a “delicate bloom on the skin.” Cansdale (1965:43) described a highly unusual color pattern for juveniles by noting that “the young brown form is pink with irregular chocolate markings that break up its outline very effectively and make it difficult to pick out in a tree or shrub.” Leston & Hughes (1968:753) described an unusual specimen from Ghana as “pale grey with darker greyish-green transverse bands, the bands irregular but more or less diamond shaped on each side. The ventrals are also grey but more glossy.”
Groves (1973:107) described the coloration of hatchlings from a captive Liberian female as “light grey background colour with pinkish undertones; black, roughly oval, lateral blotches narrowing as they approach the mid-line, where many of them fail to conjoin; top of head light grey; belly dark grey.” Rasmussen (1997a:98) noted the scales of his specimens were dull and almost dusty, a sentiment also shared by Cansdale (1965). Adult males were solid black on the dorsum and yellow on the venter (becoming black posteriorly), whereas adult females were noted to be gray, brown or yellow-brown on the dorsum and yellow-brown on the venter, sometimes without transverse bands. Hughes (2000:8) noted juvenile and subadult (approximately 1 meter in total length or less) snakes had a dorsal coloration that was “a distinctively bright and contrasting pattern of chocolate brown blotches.” He noted that most male specimens lose this coloration as they age, becoming increasingly melanistic, and although exceptions are possible, this melanistic progression does not seem to occur in females.
Chippaux (2006:154) noted there are two dorsal color morphs: (1) uniform black or dark blue with “reflets veloutés” [velvety reflections] or (2) gray with darker, poorly defined transverse spots. The venter was noted as dull yellow to charcoal gray, and juvenile coloration as light brown with darker transverse ring-shaped spots. Stucki-Stirn (1979), perhaps confused by the two color morphs (Lawson 1993; Rasmussen 1997a), described Boiga blandingi occidentalis for Cameroonian specimens that were uniform black or bluish black, whereas B. blandingi subfulva was named for Cameroonian specimens that were yellowish brown with faint whitish or dark brown diamond-shaped blotches. Lawson (1993) attributed these color morphs to sexual dimorphism, but Hughes (2000) suggested exceptions are possible. Trape & Mané (2006:168) added, although there are a few exceptions, the differences in coloration are clearly associated with the sex and age of the specimens. Greenbaum & Carr (2005:15) documented the color in life of an adult female from Guinea as “dorsum and flanks were pinkish tan with 39 brown blotches outlined in a creamy tan border along the flanks. The dorsum of the head is brown; the labials are tan with brown outlines, and the venter is white.” Pauwels et al. (2020) documented an adult specimen from Gabon that was uniformly beige in life. Based on photos of a subadult of unknown sex from Mbiliki, Cameroon (Fig. 5G) and a juvenile of unknown sex from Gamba, Gabon (Fig. 5H), the base of the tongue is bluish black, and the forked tip is silvery gray (Greenbaum et al. 2021).
Sexual dimorphism: This species is highly sexually dimorphic, with blotchy brown females and subadults, and black and yellow phase adult males.
Similar species: Pseudohaje goldii (similar to adult males), T. vexator Greenbaum et al. 2021.
RASMUSSEN (cited as “pers. comm.” in GOSSMANN et al.) states that there are no constant differences between African and Asian Boiga species.
Types: The types of Dipsas valida and Dipsas globiceps appear to be destroyed accodring to J. Hallermann (pers. comm.). The type locality of D. valida is “Edina (Grand Basso County, West Africa)”.
Type species: Dipsas Blandingii HALLOWELL 1844: 170 is the type species of the genus Toxicodryas HALLOWELL 1857.
Habitat: fully arboreal (Harrington et al. 2018).
|Etymology||Named after Dr. William Blanding (1772-1857), American naturalist and a friend of Hallowell.|
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