B. c. longicauda
[Main Page]


Natural History



Back To The Boas


We have purposely omitted tables and some data such as maps for now.  These will be included at a later date.





* Present Address: 1450 Blue Spruce Lane, Wantagh, N.Y. 11793 USA
Department of Biology, Nassau Community College, Garden City,
N.Y. 11530 USA

Abstract:  The taxonomy of the genus Boa is poorly elucidated as a result of the spotty systematic fieldwork on this wide-ranging genus.  Given current suggested modifications of the species concept, the insular taxa, nebulosa and orophias, warrant specific recognition.  Evidence for the occurrence of Boa constrictor imperator in southern Ecuador and Peru is lacking, and its retention on checklists of Peru is a literature artifact.  A new Boa, restricted to Tumbes, Peru, merits at least subspecific recognition, as it differs from all conspecifics in length of tail and hemipenis, color pattern, and is geographically isolated.

The systematics of the species Boa constrictor is in a lamentably poor state considering that it has been known to the scientific community since at least the time of Linnaeus, is one of the most widely distributed terrestrial vertebrates known, and is arguably the- most widely recognized snake in the world.  Boa constrictor is polytypic on two continents comprising a geographic range of over 6 million square miles, including five known distinguishable insular populations (at least one of which has not been formally recognized) and at least two mainland forms apparently allopatric with either of the major continental subspecies.   Our incomplete knowledge of this species is likely a result poor sampling over the extensive distributional range which has dissuaded investigators from pursuing any comprehensive study.

Recently dissatisfaction among herpetological taxonomists with the old Biological Species Concept and suggestions for new specific and subspecific criteria does allow for more latitude in analysis of the populations and demes of Boa constrictor, but will, of course, fall short of satisfying the more extreme interpretations.  We have chosen to base our determinations on the more conservative, traditional rule that two populations are subspecifically different if they different in a suite of characters to the degree of at least 75% (full species differing at the 100% level).  In many interpretations of this rule, an area of parapatry and intergradation must occur for- subspecies recognition.  We emphasize that time frame may create operational difficulties in this theory, as a current observation may not provide adequate data as to long term characteristics and fates of evolving populations.  Nonetheless, this method of subspecific determination (with minor variations) is supported by Smith (1990), who emphasizes that recognition of dichopatric populations as different species is subjective and subject to opinion, Janis Roze (pers. comm.), and Herndon Dowling (pers. comm.).

  If one accepts the Phylogenetic Species Concept of Rosen (1978, 1979), the smallest diagnosable populations of Boa constrictor with a derived character difference would be full species, including the undescribed pallid population from Islas de Bahia and Cayos Cochinos, Honduras, the new Peruvian population described herein, the isolated subspecies ortonii, and the insular Caribbean orophias and nebulosa.  The somewhat more conservative, cladistically influenced Evolutionary Species Concept (ESC) of Frost and Hillis (1990) would also elevate orophias, nebulosa, and likely the new Peruvian population to full species, as they are allopatric and appear not be reproductively compatible with other Boa.  Lazell (1964), in describing nebulosus (which should have been named nebulosa, as Boa is a feminine genus), expressed some misgivings about not according full species status to orophias and nebulosa, especially as he was concerned about their ability to interbreed with mainland forms.  He stated that he would have described orophias as a full species had nebulosa not existed to form a cline from the mainland form.  Proponents of the ESC consider allopatric clinal subspecies to be full species, particularly if they will be subsumed into the larger species in future.  We see no reason to infer that the islands of St. Lucia and Dominica (as a single unit) will afford boas opportunity for genetic exchange with the mainland barring major tectonic catastrophe.  Stull (1935) placed these Lesser Antillean forms of Boa in the species orophias, as a consequence of their insular occurrence on St. Lucia and Dominica and their substantial phenotypic differences from mainland Boa.  We concur, these snakes being 100% genetically isolated from the mainland, although it is uncertain whether they comprise one species or two.

  Insufficient data is available on the Honduran insular populations to make a determination of their proper taxonomic rank.  Peters and Orejas-Miranda (1970), and Vanzolini (1986) consider the insular Panamanian sabogae a subspecies based on traditional methodology.  The distance from Saboga Island to Panama is not sufficient for a determination of reproductive isolation to have been conclusively made.   Zweifel (1960) has placed sigma in the synonymy of imperator based on traditional criteria.  Again, the distance from the Tres Marias Islands to Mexico proper is insufficient for isolation or important character variation.

The Peruvian Boa Fauna

    Despite the facts that Boa constrictor has never been reviewed in its entirety and the relationships between the two major contiguous subspecies, constrictor and imperator, are poorly elucidated, there exist several insular and/or relictual subspecies recognized by nearly all workers (vide supra).  Several American  workers (Wilson and Meyer, 1985) have argued against new or additional Boa subspecies and have, in fact, called a taxonomic system archaic. While the authors stand apposed to the naming of gratuitous or dubiously documented taxa at any level, as has recently been the case with Lampropeltis Triangulum, and possibly with Boa constrictor Melanogastor, (Lang hammer, 1983), we are compelled to formally report as new such taxon as merits hierarchical level.  Having found a population of Boa  which has evolved sufficiently to appear unique, we herein describe a new subspecies from a relictual area in Tumbes, Peru.

  Part of problem in assessing subspeciation in Peruvian Boa constrictor is the lack of certain geographic ranges for the known taxa.  Stimson (1969) and Peters and Orejas-Miranda (1970) both list the southernmost range B. c. imperator and the only range of B. c. ortonii as northwestern Peru.  Schmidt and Walker (1943), list only B. c. ortonii as occurring from Piura south to Libertad.  Assuming acceptance of the validity of ortonii, only the province of Tumbes lies outside its range on the northwest coastline of Peru, and the snake inhabiting this province is unique.  We would accord it specific status, were we absolutely certain that no intergradation with B. c. imperator occurs, although none has been documented.

  With regard to Boa constrictor melanogastor, Langhammer’s (1983) poor taxonomic procedure renders this name a nomen dubium, although it may well be a recognizable taxon.  His most egregious error is his blatant disregard for the high dorsal scale counts of B. c. constrictor documented by such respected workers as Lazell (1964), Dixon and Soini (1977, x=929.2 for seven specimens) and Vanzolini, Ramos-Costa and Vitt (1980).  These counts were later supported by Chippaux (1986) who examined 15 specimens from Guyana with 91 to 95 mid-dorsal scales.  Langhammer stated that snakes with dorsal counts in excess of 88 were most likely misidentified melanogastor.  The inference that melanogastor inhabits Guyana and Caatingas, Brazil as well as Ecuador is untenable.  Also worthy of note is Langhammer’s (1983) contention that melanogastor has mid-dorsal saddles only 4-7 scales in length; his photograph of the holotype shows that while this is true for saddle number 10, saddles number 6 and 7 cover 10 scales, and saddle number twelve covers 8 scales.  Langhammer admits to being unsure of the range of melanogastor; he states (1983) that the range should overlap into the Amazonian areas of northern Peru, where Dixon and Soini (1977) have, in fact, documented the occurrence of subspecies of constrictor.  Finally, we are left with no criterion to distinguish this population from constrictor except the dark ventral surface, whose status at the area of intergradation with constrictor remains uncertain.  Nonetheless, Langhammer's tables of meristic counts are fairly complete and well documented.  His assertion that imperator has 22 or more dorsal saddles is supported by hundreds of observations, however, his support for the traditional assumption that B. c. constrictor has 21 or fewer saddles is not entirely correct, as we have seen 2 specimens from Colombia with 22.   This being the case, ortonii, which have 15-19 body saddles and the Tumbes "black boas" with 19-21 cannot be imperator sensu Langhammer (1983).  The inference that imperator occurs in Peru at all thus lacks support.  Its retention as a Peruvian taxon in recent accounts (Langhammer, 1983; Peters and Orejas-Miranda 1970) is thus either artifactual or suppositional, as the Tumbes population was not well known until 1987.  We thus propose a restriction of the range of imperator to southern coastal Ecuador, an area poorly represented in museum collections.

With regard to the "black boas" of Tumbes Province, Peru, the data for taxonomic recognition is much more convincing.  These snakes differ in numerous respects from both subspecies imperator and constrictor, and are isolated from the latter by mountains almost 3000 meters feet in elevation.  We thus describe them below as:

Boa constrictor longicauda subsp. nov.

Holotype. --Museum of Comparative Zoology (MCZ) 176002, a subadult male, was collected on June 14, 1988, east of Tumbes, Tumbes Province, Peru, by a native collector.

Paratypes.--MCZ 176003, an adult male (illustrated on cover plate), collection data same as for holotype, is represented by a complete shed skin, the specimen still extant (RMP 551, collection of the senior author) to be donated to MCZ upon its demise.   RMP 553, a subadult male, was collected in 1989 in Tumbes Province, Peru, obtained from importer, no further data available.

Diagnosis. --Boa constrictor longicauda may be distinguished from all conspecifics by the much longer tail (in the male) and hemipenis.  Additionally, it may be distinguished from B. c. imperator by fewer dorsal body blotches (20-21 in longicauda, 22 or more in imperator), the longitudinal mid-dorsal band without projections to the eyes, and the generally darker head and body coloration, without tan or red color on the tail in adults; from B. c. constrictor by lack of red coloration on the tail, fewer midbody scale rows (a maximum of 76, usually fewer in longicauda, a minimum of 81, usually several more in constrictor), the darker body pattern without tan color, and the grey, black-spotted head in adults; from B. c. ortonii by the much darker overall coloration, lack of red tail color and lower ventral count (246-252 in ortonii); from B. c. melanogastor (sensu Langhammer, 1983) by the much longer tail, lack of melanistic ventral coloration, and fewer middorsal scale rows (86 or more in melanogastor); from B. c. amarali by the overall darker coloration, greater number of subcaudals (43-52 in amarali), and fewer dorsal body saddles (22 or more in amarali); and from B. c. occidentalis by the greater number of subcaudals (45-46 in occidentalis), and the very different color patterns (a blackish network or reticulum on a cream ground color in occidentalis).

  Description of Holotype. --The following description was made postmortem on the as yet unpreserved specimen.  The holotype is a small adult male 159.5 cm in length with a 23.6 cm tail.  The tail/total length ratio of 0.148 is the longest documented for any specimen of Boa.  The head is grey with a few black-specks and a mid-dorsal longitudinal spear-shaped black band which bulges laterally at the level of the eyes.  It has thick black pre-ocular stripe from the nostril narrowing at the eye, and a post ocular stripe underlined with a narrow white band extending past the angle of the jaw.  The tip of the snout is slightly abraded.  It has 19 mid-dorsal body saddles, 7-10 scales in length at midbody.  The first 4 saddles are connected by lateral bands.  These saddles are almost entirely black, numbers 4 to 14 having elongate white patches in their lateral expansions.  There are 23 lateral body blotches, charcoal gray and 5 scales long anteriorly, originating on the third or fourth scale row, becoming progressively darker and longer posteriorly, reaching a maximum of 18 scales in length, originating on scale row 1 posteriorly.   Several of the posterior body blotches have white centers.  The flanks are grey, the interspaces between the saddles dark brown.  The ventral ground color is cream and almost without spotting on the anterior 1/3 of the body, laterally spotted and flecked with black on the middle 1/3, and heavily spotted with black on the posterior 1/3 of the body.  'There are 4 black dorsal tall blotches with a black tail spine.  The underside of the tall is cream, with 4 large black spots, each 4 to 4 1/2 subcaudals long.  There is no red coloration on the tail.  The ground color of the tail is yellow.

There are 247 ventrals and 62 subcaudals.  The dorsal scutellation is 54 at the neck, 66 at midbody, and 38 at the tail.  There are 20 supralabials and 22 infralabials.  The infralabials are lightly flecked with black.  The hemipenis probed 40 subcaudal scales while the animal was alive, and the right organ subtended 29 subcaudals when everted (but not fully turgid, retractor muscle not cut).  The left hemipenis is partially everted.

Remarks. --The holotype is one of only 2 specimens with 19 dorsal saddles; it appears to be congenitally missing the first dorsal body saddle.

Variation. -A total of IO males and IO females were included in this study.  Males mature sexually at about 150 cm, and both sexes attain lengths in excess of 280 cm.  There are 19 to 21 black dorsal body saddles, 7-10 scales in length at midbody, often joined anteriorly by lateral stripes, but separate posteriorly.   There are 4 to 6 black or brown-black dorsal tall blotches.  The head surface ranges from gray to charcoal with a coal black longitudinal middorsal spear shaped band which may send small lateral projections toward, but not reaching the eyes, and there may be a sub ocular black projection not reaching the upper labials.  Suffusion of black on the head, snout, and infralabials is highly variable, the paratype having numerous dark flecks and spots.  There is pronounced ontogenetic variation in the color of the flanks; juveniles having brown flanks which change to gray or black in a period of less than two years as maturity is reached.  Adults may develop extensive white patches on the flanks and in the lateral aspects of the saddles.  The interspaces between the saddles are brown in younger specimens, but become strongly suffused with black in larger snakes (see illustration of paratype).  There are 50 to 58 (x=54.0) dorsal scales around the neck, 60 to 76 (x=67.7) at midbody, and 32 to 40 (x=37.9) posteriorly.  Ventrals range from 223 to 247 (x=239.2), and subcaudals from 60 to 67 (x=62.8) in males and 50 to 54 (x=52.7) in females.  The tall is long, comprising 11.1 to 12.0 percent of the total body length in females, and 12.8 to 14.8 percent in males.  There is significant sexual dimorphism in tail length.  The hemipenis probes 36 to 40 subcaudals.

  Distribution. --B. c. longicauda is known only from Tumbes Province, Peru, the only coastal tropical wet forest in Peru.

  Etymology. --The name longicauda is Latin for "long-tailed."

  Discussion  Boa constrictor longicauda has a longer tail than other subspecies, and there is significant sexual dimorphism at the .02 level by Student's t test, the males' tails averaging 14.1% of total body length, the females 11.6%.  Although the literature contains inadequate analyses of tail length to total length ratio in other populations to make a statistically valid statement, it is worthy of note that there are no records for other males with tails as long as B. c. longicauda.  Dixon and Soini (1977) list figures of 11.9 and 11.4% for males and females of B. c. constrictor from Iquitos, Peru, although their samples were quite small.  We have found similar measurements in Colombian constrictor.  Our ratios for 3 male specimens of Colombian imperator and 2 ortonii fall between 10.6 and 11.0%.

  In the past many workers considered Boa to possess a proportionately small hemipenis.  This may be a result of' Cope's (1900) often cited 85 mm hemipenial illustration of a specimen from Brazil.   Cope died before the plate section of this text was finished, however, and there is no further data or scale included with the drawing.  The authors have observed an everted hemipenis estimated to be in excess of 220 mm on the specimen herein illustrated.  Inverted, the same organ subtended 38 subcaudals on the 221 cm specimen.  The maximum hemipenial probes we have recorded for other subspecies are: constrictor, 27 subcaudals; imperator, 23 subcaudals; melanogastor, 28 subcaudals; ortonii, 14 subcaudals.  Given the differences, it is questionable whether large male longicauda could successfully copulate with other subspecies.  The single male observed in copula shows no interest in females of other subspecies.

  Boa constrictor longicauda is almost certainly confined to Tumbes Province, a wet tropical refugium surrounded to the north, east, and south by cordillera rising to at least 3000 km.  The only possible access for other subspecies to Tumbes would be by Pacific coastal drift from Ecuador.  The large Peruvian collection at the Museum of Comparative Zoology at Harvard University includes no Boa specimens from Tumbes or adjacent southern provinces of Ecuador (Jose Rosado, pers. comm.).

  While the phylogeny of the subtaxa of Boa remains speculative, Stull (1932) implies the existence of a constrictor group within the genus, with amarali intermediate between constrictor and occidentalis geographically and with respect to the mental shield.  Melanogastor sensu Langhammer (1983), must be added to this group based on meristic and mensural characters.  An imperator group is also implied by Schmidt and Walker (1943) and Zweifel (1960) consisting of at least subspecies imperator, sigma, and ortonii.  The derivation of the insular orophias and nebulosa is problematical; Lazell (1964) correctly points out that their geographically closest neighbor is constrictor of Trinidad and Tobago, some 350 kilometers to the south, and that a stepped cline series exists with respect to meristic and mensural characters.  It must be bourne in mind that the Isthmus of Panama has only existed for 3-4 million years in recent times, therefore imperator may be a relative newcomer to Central America and Mexico.  The likelihood that it crossed over 2000 kilometers of the Caribbean to reach St. Lucia and Dominica in such a short time is slim.  The likelihood of a recent relationship between imperator and longicauda is greater, as their ranges approach parapatry and the scale meristics are close.  Ultimately, many of these relationships may only be resolved through biochemical analyses, if at all.

  Specimens Examined.--With the exception of the holotype, all 20 specimens are currently in private collections,  including 7 in the collections of the authors. All counts and measurements were done at least two times on living snakes except for the holotype and shed skin of the paratype.

[Back To Top] [Back To The Boas] [Main Page]



Longicauda1HDTP.jpg (79384 bytes)

Longicauda2HDTP.jpg (56958 bytes)

Longicauda3HDTP2.jpg (68756 bytes)

BclongicaudaTimeMeade91male.jpg (68293 bytes)

1991 Male - Photo courtesy of Tim Meade.

BclongicaudaTimMeade91female.jpg (78948 bytes)

1991 Female - Photo courtesy of Tim Meade.

BclongicaudaTimMeade92female.jpg (54581 bytes)

1992 Female - Photo courtesy of Tim Meade.

BclongicaudaTimMeademalewildcaught.jpg (65440 bytes)

Wild caught male - Photo courtesy of Tim Meade.

[Back To Top] [Back To The Boas] [Main Page]