Members of the genus occur from southeastern Guatemala, through much of Central America (although the distribution can be disjunct), into South America, with a limited distribution west of the Andes in Colombia and Ecuador. East of the Andes the genus is widespread in the Guianas, Amazonia and the Atlantic Forests of southeastern Brazil.
In the West Indies species occur on Isla de Margarita, Trinidad, Tobago, St. Vincent and Grenada banks. Corallus species have conquered a wide range of habitats from sea level to 1100 meters above sea level. All members are arboreal and inhabit contiguously forested areas .
Early map of the Lesser Antilles, 1660.
Taxonomic history of the Treeboas
CHANGE OF SURINAMIC INSECTS. THE XLVL IMAGE. Smelling Jasmin, wafting wildly through malkander in Surinam, like the hedges in Europe, giving such a strong smell of fig that one can smell it from afar. Among these bushes her ordinary remembered a multitude of Lagedifins, Iguanas, and Snakes, therefore I have added here a beautiful and weird Snake, whom I have caught under the Hedge at the foot of these plants; which Snakes have a very famous way of rolling fig together, and hiding her head in their own circles. Drawing of Corallus hortulanus by Mary Merian, 1705.
A taxonomic review is in order to unravel the long and tortuous journey of the name Boa, enydris, hortulanus, Corallus, cookii, ruschenbergerii and grenadensis. McDiarmid, Toure & Savage (1996) went to great lengths to determine the proper nomenclature of the ubiquitous common Treeboa. Linnaeus originally classified nine snake species of the genus Boa in his seminal work. Two of them were Boa enydris (1758: 215) and Boa hortulana (1758: 215-216).
Both the B. enydris and the B. hortulana specimens were from “America”. B. enydris was based on a specimen in the museum collection of Swedish entomologist Carl de Geer. B. hortulana was based on a specimen from Mus. Ad. Fr. by Linnaeus (1754) and 2 plates from Seb. Mus. 2 (Seba 1735). Figure 1 of plate 74 is a specimen Seba called “Vipera, Paraguajana, formosa” or “Vipere du Paraguay” found in Amerique Meridionale. Seba had, in figure 1 of plate 84, drawn what he called “Couleuvre Tlehua, ou Ignee, belle de Nouvelle Espagne” or “Coluber de Tlehua, seu Igneus, perpulcher”.
Linnaeus, in his description of B. hortulana, wrote the head had yellow-golden splotches resembling a garden. Shaw (1802), used this reference by Linneaus to name B. hortulana the “Garden Boa.” The “Garden Phase” in use today is in reference to the brown or dark colored C. hortulanus.
The long and winding (taxonomic) road
As outlined below, one can visualize where and when the three species we are concerned with were described and named. These three species are covered in more detail in their accounts. The synonymy is extrapolated from the individual material listed and .
The genus Corallus was erected by Daudin in 1803 when he was describing the boa Corallus obtusirostris (a synonym of Corallus hortulanus) . He originally reasoned the erection of the new genus as follows (translated from french):
The research I have done so far, in the collections of Paris, convinced me that the boa bojobi (canine boa Lin. ) is a species essentially different in shape, color, scales and its plates, from the snake that Merrem included in his Natural History of Amphibians, fasc. 2, pi. 11. This author calls it the blunt-headed boa, and is uncertain whether it is a separate variety or species from the boas bojobi and enydre. I have noticed, under the neck of the figure of this animal, that the first two plates are double; and as I believe that this character is constant for all individuals, I have used it to establish the genus Corallus.
Stafford provided a brief description of the general characteristics of Corallus: “highly developed arboreal species characterized by a slender, laterally compressed body, a large pear-shaped head well defined from the neck, greatly enlarged anterior teeth and a series of heat sensory pits between the labial scales of the upper and lower jaw. The tail is elongate and strongly prehensile” .
Henderson provided a similar definition of the genus, however, pointing out that Corallus cropanii differs in scalation and overall appearance (body is less compressed). He also noted that Corallus exhibits little sexual dimorphism in traditional meristic characters. Regarding the scalation Henderson wrote: “Dorsal scales are in 29-77 rows at midbody, ventrals 179-294, and subcaudals 51-141. Subcaudals in all species of Corallus except C. cropanii are usually >65. Some supralabials and infralabials have deep pits“.
He describes the dorsal color and patterning in the genus as highly variable, whereas the ventral ground color is white, cream, beige, bright yellow, or dingy yellow. The venter may be immaculate to heavily patterned and the posterior portion of the venter is almost invariably more heavily patterned than the anterior portion. He noted that no other New World boine can be confused with any species of Corallus .
Taxonomic history Part II
The easily recognizable species Corallus caninus (sensu lato) revealed only recently its cryptic diversity and is now considered as two separate species: Corallus batesii and Corallus caninus . Much more complex is the situation of the members of the Corallus hortulanus complex: Corallus annulatus, Corallus blombergii, Corallus cookii, Corallus grenadensis, Corallus hortulanus and Corallus ruschenbergerii.
Each of these Treeboa species shows a high degree of variation in color and pattern and at the same time shows similarities or overlaps to its congeners. Therefore, confusion while identifying boas of the Corallus hortulanus complex has been and still is commonplace. Add to the story the difficult nomenclature situation and you will understand that hobbyists as well as scientists could be talking about the same species yet using different scientific names, or could talk about different species using the same name.
The misrepresentation and hybridization (intentional or unintentional) of different species/subspecies by hobbyists and professionals alike, hasn’t exactly helped to improve the situation. Thanks to the large body of work contributed by Robert W. Henderson and other scientists, insights about taxonomy, natural history, ecology and conservation continue to shape, and reshape, our picture of the Genus.
Three species are known to inhabit the West Indies. These are Corallus cookii occurring on St. Vincent, Corallus grenadensis occurring on Grenada and some of the Grenadines as well as Corallus ruschenbergerii, occurring on Trinidad and Tobago . It should be noted that an initial genetic analysis of Corallus cookii and C. grenadensis did not justify their separation from C. hortulanus. The authors state, however, that additional studies of these taxa that include better sampling, additional loci and explicit tests of alternative species hypotheses using coalescent methods for species delimitation are needed to properly address their status .
Henderson, the authoritative person on C. grenadensis and C. cookii, (and Corallus in general) argues from an ecological perspective that their rank as species is justified by insular distribution as well as based on their (trophic) ecology . We here follow his argumentation and treat both forms as full species, because we think that while genetics are currently pointing in the opposite direction, the differences in natural history and ecology are vast and justify treatment of these forms separately from hortulanus. Moreover, we think that information about these forms needs to be independently comprehendible and not blended with information about mainland forms.
In regards to other Corallus species on the West Indies Mole and Urich, as well as Brown, recorded two more species species from Trinidad. These have not been recognized by later publications about the Island. Brown noted that Xiphosoma hortulana (= Corallus hortulanus) occurs on Trinidad. He obtained a specimen collected by Mr O’Reilly and differentiated this from the Corallus ruschenbergerii from Trinidad, which he described in the same publication, by pholidosis as well as coloration . It appears unclear if the collection data of this specimen was falsely assigned or if a population of C. hortulanus or other Corallus species existed (still exist?) on Trinidad. Furthermore Mole and Urich report a species they refer to as Corallus cooki var. (variety) melanea next to Corallus cookii var. ruschenbergeri (= Corallusruschenbergerii) .
Stafford was, to our knowledge, the last to mention the name and considers C. cookii var. melanea as a color form of – what was then considered – C. cookii . Presumably, Gray was the first to describe the subspecies or variety var. melanea. In his Catalogue of the Specimens of Snakes in the Collection of the British Museum, he specifies four different varieties based on coloration and pholidic characters of Corallus hortulanus (sensu lato). The two specimens which were used to define the “var. melanea” originated both from the West Indies, unfortunately only one of them was with the exact island location of Saint Vincent . Further work on the history of these museum specimens as well as on Trinidad will hopefully solve this puzzle.
Evolution
The genus Corallus is a member of the Subfamily Boinae, a group with clear Gondwanan origins . The work of Colston et al. suggests that Corallus initially emerged within mainland South America during the Eocene and diversified multiple times within mainland South America (C. annulatus, C. caninus, C. cropanii, C. hortulanus, C. ruschenbergerii) dating to the Oligocene and Miocene .
It was previously suggested that dispersal events lead to the colonization of the West Indies and Central America . The study of Colston et al. solidified this hypothesis as it provided evidence for two dispersal events over water: once to Central America (C. annulatus) and once to the Lesser Antilles (C. cookii, C. grenadensis) and a third dispersal to Central America via the traditionally recognized Panamanian land bridge (C.ruschenbergerii). The timing of speciation events within South America suggest possible roles for marine incursions, and the uplift of the Andes, but all South American species arose prior to the Pleistocene, rejecting a role for refugia in speciation.
Corallus Species Tree, Colston et al. 2013.
Species
Corallus annulatus– The Annulated Tree Boa from Costa Rica, Panama, Guatemala. Nicaragua, Belize, Honduras, Colombia. This boa is strikingly beautiful and has been kept and bred in terraria for, at least, the second half of the last century .
Corallus batesii – The Amazon Basin Emerald Tree Boa occurs in Brazil, Colombia, Ecuador, Peru and is restricted to the Amazon Basin rainforest. Only recently was it elevated to full species status; populations from south of the Rio Negro are significantly distinct from the northern congeners with which they were once considered one species (Corallus caninus) . Corallus batesii is and always was considered a very beautiful and highly sought after species in terraria.
Corallus blombergii – Blomberg’s Tree Boa. Initially thought to be restricted to Ecuador, recently discovered from Colombia . We are unaware of any specimens in private collections or Zoos outside of Ecuador. The pholidosis and color/pattern largely overlap with Corallus annulatus making the justification of the rank as species doubtful.
Corallus caninus – Has a wide distribution in the Guyana Shield in South America and is commonly kept and bred in terraria in Europe and the Americas.
Corallus cookii– This species occurs only on the island of St. Vincent in the West Indies. The population in Terraria is small. Genetic analyses did not provide convincing evidence that this species is different from Corallus hortulanus .
Corallus cropanii – This boa was discovered in 1953 and occurs in the tiny remnants of the Atlantic Rainforest of Brazil. It was thought to be extinct and was only recently rediscovered . It is highly threatened by habitat loss.
Corallus grenadensis– This boa occurs only on Grenada and some of the Grenadine Islands (West Indies). A small population exists outside its natural habitat in terraria in Europe and America. Genetic analyses did not provide convincing evidence that this species is different from Corallus hortulanus .
Corallus hortulanus – This boa occurs widespread on the south American continent and commonly kept in terraria in America and Europe.
Corallus ruschenbergerii– This boa occurs from Venezuela to Costa Rica on the South- and Mesoamerican continent. In the West Indies it occurs only on the islands Trinidad and Tobago. Small populations of this species exist in terraria in America and Europe.
Tree Boas in vivaria
Tree boas of the Genus Corallus have a long history as precious gems in hobbyist and zoo collections alike (see e.g.
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Murphy, J. B., Barker, D. G., & Tryon, B. W. (1978). Miscellaneous Notes on the Reproductive Biology of Reptiles. 2. Eleven Species of the Family Boidae, Genera Candoia, Corallus, Epicrates and Python. Journal of Herpetology, 12(3), 385. https://doi.org/10.2307/1563620
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Pinto-Erazo, M. A., & Medina-Rangel, G. F. (2018). First record of Corallus blombergi (Rendahl & Vestergren, 1941) (Serpentes, Boidae) from Colombia. Check List, 14(1), 183–188. https://doi.org/10.15560/14.1.183
Polanco, J. M. (2006). Emerald Gems (Corallus caninus): Captive Husbandry and Propagation Part I: Introduction and Habitats. IGUANA, 13(1), 37–41.
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Stafford, P. (1986). Notes on the distribution, habits, and various color morphs of Cook’s tree boa (Corallus enydris cookii Gray). Litteratura Serpentium, 6(4), 147–153.
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