Corallus ruschenbergerii

Scientific Name

Corallus ruschenbergerii   
Corallus ruschenbergerii Photo Danny Cueva
Obtained by Dr. William Samuel Waithman Ruschenberger (1807-1895), a physician in both the U.S. Army and Navy and President of the Academy.  Described and dedicated by Edward Drinker Cope (1840-1897), a renowned zoologist of great merit.

Holotype

ANSP: No. 10325, collected at Panama by Dr. W.S.W. Ruschenberger
USNM: No. 53896, collected by Meek & Hildebrand, Panama.
MNH: No.’s 41808 and 42230, collected by Grant, Canal Zone, Panama.

Type Locality

Panama.

Subspecies

None.

Synonyms

Common Name

Mangrove Treeboa, Ruschenberger’s Treeboa, Black-tailed Treeboa.  On Trinidad the snakes are called Cascabel or Cascabel Dormillon (= patois for “Sleeping Rattlesnake”).  Called the Greater Treeboa on Isla de Margarita.

Description and taxonomic notes

Trinidad:  Laterally compressed body, SVL of 1870 mm*, ventral scales number 252-268, subcaudal scales 100-112, dorsal scale rows at midbody 38-45, scales between supraoculars 3-10 (6 modally), circumorbital scales 11-16 (13 modally), supralabials 10-12, loreal divided, loreal rows 2-3, infralabials 12-15, subloreal scales 2-6 (3 modally), # of scales bordering nasals 4-6, # of scales between supraoculars 3-9, loreolabials 4-8, scales around the eye 12-15, dorsal body blotches 36-39. **

Tobago:  Laterally compressed body, SVL of 1790 mm, ventral scales number 250-264, subcaudal scales 101-111, dorsal scale rows 38-48, scales between supraoculars 3-10 (6 modally), circumorbital scales 11-16 (13 modally), supralabials 10-11, loreal divided, loreal rows 2, infralabials 13-16, subloreal scales 2-4 (3 modally), # of scales bordering nasals 4-6, # of scales between supraoculars 3-9, loreolabials 4-8, scales around the eye 12-15, dorsal body blotches 36-41. **

Isla de Margarita:  Laterally compressed body, total length 900 mm- 2500 mm, ventral scales 250-285, subcaudals 94-118, loreal divided, 1-2 preoculars, small suboculars and several postoculars, supralabials separated from the eyes by a single row of scales, scale rows at midbody 38-49. ***

An interesting graph depicting the weigths of the Corallus species accessible to the author.

*  A preserved museum specimen with a stub tail measured 2311 mm.
** Data from , .
*** Data taken from .
C. ruschenbergerii meristics. *

* Taken from , , .

Corallus ruschenbergerii females, Trinidad locale.

Mole and Urich investigated C. ruschenbergerii from Trinidad. They state that adults attain a length of seven or eight feet (2133 mm – 2438 mm). They report that the body coloration is sometimes yellowish-brown, but more often deep dark brown. Each scale is of a dark brown color at the extremity furthest from its attachment to the skin, but underneath, where they are overlapped by the other scales, they are pale or bright yellow. Many individual scales have a white border at the base of each scale giving the impression, when viewed up close, of emitting light.

Corallus ruschenbergerii

The ventral scales are dark brown and rich yellow, sometimes punctured with black. The authors were fascinated by the beautiful iridescent blueish colors and the pattern the snakes display in direct sunlight. The snakes have large and prominent eyes with a vertical pupil . Brown obtained two live specimens collected by O’Reilly from Trinidad. The specimens were of similar size, total length 1680 mm and 1655 mm, tail length 305 mm each. The coloration of the snakes was greenish brown with an occasional yellow scale, one specimen had no yellow coloration in it .

Two C. ruschenbergerii with different ground color.

Henderson and Boos analysed a total of thirty-five specimens of C. ruschenbergeri from Trinidad and six specimens from Tobago. They found that the tree boas, on average,  were larger than the mainland specimens. The largest specimen from Trinidad had a SVL of 1870 mm and the largest from Tobago measured 1790 mm SVL .  Logic dictates island fauna would tend to be smaller than it’s mainland sister species as a result of habitat and prey, among other limitations.  These island treeboas are testament to the exception rather than the rule.

Distribution

Trinidad, Tobago and Isla de Margarita, and Isla de la Cocche in the West Indies.  The Isla de la Cocche population is newly found, October 2022, and is a range extension for the species.  On the mainland the treeboa is found in Venezuela (north of the Rio Orinoco and north-west of the Guiana Shield), Colombia (in the llanos east of the Andes and north of the Central and Oriental cordilleras), Panama (and the offshore islands Isla de Cebaco,  Isla Contadora, Isla del Ray, Isla Suscantupu) and southern Costa Rica.

Costa Rica Corallus ruschenbergerii in Quepos, Puntarenas. Mainland boas are more boldly marked. Photo Randall Jimendez
Panama C. ruschenbergerii. Photo Loes Roos
Venezuelan Corallus ruschenbergerii. The Venezuelan and Colombian forms are much more brightly colored than the insular locales.  Photo Danny Cueva
Eastern Tobago Corallus ruschenbergerii. Photo Renoir J. Auguste
Trinidad C. ruschenbergerii in the Caroni Swamp Bird Sanctuary. Photo Ryne Rutherford
Colombia Corallus ruschenbergerii, Riohacha La Guajira. Photo Russ Manning

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Habitat

On Trinidad and Tobago the mean annual temperature is 26.05°C and the mean annual precipitation is 1604.99 mm.  Average rainfall in the north and northeast is 2880 mm and 1200 mm in the west and southwest. The Trinidad weather is tropical and there are only two seasons which can be observed throughout the year: those are the wet season and the dry season. The first six months each year are considered the dry season while the second half would be the wet season with a three week dry spell around September and October.  Most of the winds to hit the island come from the northeast. Because of its location Trinidad is usually safe from hurricanes though some in the past have come really close to causing damage. The temperatures are usually very stable in Trinidad.

Trinidad is traversed by three distinct mountain ranges that are a continuation of the Venezuelan coastal cordillera. The Northern Range, an outlier of the Andes Mountains of Venezuela, consists of rugged hills that parallel the coast. This range rises into two peaks. The highest, EI Cerro del Aripo, is 940 meters high; the other, EI Tucuche, reaches 936 meters. The Central Range extends diagonally across the island and is a low-lying range with swampy areas rising to rolling hills; its maximum elevation is 325 meters. The Caroni Plain, composed of alluvial sediment, extends southward, separating the Northern Range and Central Range. The Southern Range consists of a broken line of hills with a maximum elevation of 305 meters.

There are numerous rivers and streams on the island of Trinidad; the most significant are the Ortoire River, fifty kilometers long, which extends eastward into the Atlantic, and the forty-kilometer long Caroni River, reaching westward into the Gulf of Paria. Most of the soils of Trinidad are fertile, with the exception of the sandy and unstable terrain found in the southern part of the island.  The forest make-up of Trinidad can be classified as lowland moist, degraded lowland moist, submontaine, montane, degraded montane, swamp, mangrove and dry.  There are approximately 17 areas consisting of mangroves ranging from 9 ha (Godineau Swamp) to 37.3 km² in the Caroni Swamp .

Tobago is mountainous and dominated by the Main Ridge, which is 29 kilometers long with elevations up to 640 meters. There are deep, fertile valleys running north and south of the Main Ridge. The southwestern tip of the island has a coral platform. Although Tobago is volcanic in origin, there are no active volcanoes. Forestation covers 43 percent of the island. There are numerous rivers and streams, but flooding and erosion are less severe than in Trinidad. The coastline is indented with numerous bays, beaches, and narrow coastal plains.  Tobago has several small satellite islands. The largest of these, Little Tobago, is starfish shaped, hilly, and consists of 120 hectares of impenetrable vegetation.

Mohammed and co-workers could find Corallus ruschenbergerii in four different habitat types at their study site in south east Trinidad.  These were forest edge, littoral woodland, palm forest, swamp forest .  According to Schwab the species could be found in the Aripo Savannah .  Mole and Urich state that the species is frequently found in bamboo clumps, and in bushes in the vicinity of or overhanging streams and are often found in the trees on the banks of the Caroni river .

C. ruschenbergerii resting in a tree in the Caroni Swamp, Trinidad. Photo Rich Kostecke

Auguste found the species in three different sites on Trinidad and Tobago. These were the Caroni Swamp, Nariva Swamp located on Trinidad and the Main Ridge Forrest Reserve on Tobago (the oldest forest reserve in the New World)  . Sexton and Heatwole reported from Panama that they collected three adult specimens and one juvenile near the mouth of the Canclon River. The Canclon area is heavily forested except on the river banks which were at the time inhabited by Choco Amerindians. One boa was found 10 meters above the water in a tree, another 3 meters above water level in a tree. .

C. ruschenbergerii habitat Venezuelan llanos, Apure Province. Photo Danny Cuevas

These observations are largely in line with Henderson’s work, stating that the distribution of the species largely excludes tropical rain forest on the mainland . However, Barrio-Amorós notes that Corallus ruschenbergerii has been reported occassionally in lowland coastal rainforests in the states of Aragua, Carabobo, and Miranda. He added observations from Daniel Calcaño of an adult C. ruschenbergerii observed at El Playón, Río Caura, Estado Bolívar (6º19’37”N, 64º31’43”W, 55 m asl), in deep Orinoquian rainforest. The observer stated that C. hortulanus and C. ruschenbergerii occur in microsympatry, however, C. hortulanus has been observed 10 times more in these habitats than C. ruschenbergerii .

On Isla de Margarita C. ruschenbergerii is found in coastal mangroves, deciduous and semi-deciduous forests .  Found at San Francisco de Macanao (Roze, 1964), Los Cedros (Roze 1966), Quebrada Piedra Goteadora, near Punta Arenas on the western portion of the island , 10 km west-southeast La Asuncion (Henderson 1997) and around Cerro El Tamoco in Paraguachoa.  Locals report the treeboa is common around Laguna Las Marites .  Isla de Margarita is the second largest island off the coast of Venezuela; only Trinidad has a larger surface area.  The treeboa can be found up to 400 meters.

Longevity

It is unknown how long lived the boa is in situ.  In captivity they are long lived; one of the authors had a specimen that was imported as an adult in 1993 and it passed away in 2012.

Reproduction

Mole and Urich note on the reproductive biology: “These snakes couple in the months of February, March, and April. Mr. O’Reilly caught a pair coupling in February, and the young were produced the following August. They have coupled in our cages in February, March, and April. They produce some 20 or 30 young ones at a time, generally about August and September“. However, they state that they obtained a very young wild caught snake in May, thus, questioning the reliance of a specific breeding time. They state that “The young ones are very small and thin, with enormous heads, and probably their first meals consist of small lizards, such as Anoles alligator, very young birds, mice, and rats. The lizards they constrict. They are soon able, however, to catch full-grown mice, and it is really wonderful how the young snakes manage to pass down their excessively slender necks, which are not so thick as a lead-pencil, adult mice” .

Ball of C. ruschenbergerii in the Caroni Swamp, Trinidad. Photo Chris Charlesworth
The waxy appearance of the scales is a complex process that involves lipid changes in the males. Males will remain like this throughout breeding season until they shed again.

The breeding time for mainland specimens seems to differ from the island animals as observed by Barrio-Amorós; he found a total of seven C. ruschenbergerii in the gallery forest of the Río Apure (Llanos ecosystem). One large female about 180 cm long and six males, one of which was mating and the others approaching. The author felt reminded of the mating balls seen in Anacondas (Eunectes) in an arboreal fashion. He did not observe this behavior before or after and thus questions whether this was a common occurrence or just an extraordinary event. He found very young treeboas usually high in the canopy during the rainy season (May through September). . The observation by Mole and Urich seems to confirm this observation. They report that during breeding season, many snakes are found in the localities they frequent in close proximity .

Trinidad C. ruschenbergerii mating.
Gravid Corallus ruschenbergerii, Trinidad locale.

Henderson and Boos report a litter of C. ruschenbergerii from Trinidad; the young measured 415 mm – 452 mm SVL and weighed 18g – 20g .

The difference in mating time from island to mainland is an interesting phenomenon and and one can conclude that while seasonal changes in daylight hours might contribute to mating  activities, they are not strongly dependent on them, but rather a result of seasonal climate variation such as precipitation, humidity and temperature.

In captivity mating in C. ruschenbergerii from Costa Rica takes place during the months of  December through March and September through December with litters born in August (Booth, McPeek pers. comm.).  Potential litter size is 14.

C. ruschenbergerii from Trinidad mate in May and June with parturition occurring in October and November.  Litter size ranges eight to thirteen large neonates.  Average weight of a newborn ranged from 20.57 g in one litter to 21.49 g in another.  Average SVL of a neonate is 38.53 mm.  All boas shed between four and 10 days after birth and started feeding on large fuzzy mice or pink rats on day nine and afterwards.  The neonates showed a preference for larger rodents than experience dictated.  Of the ten neonates, 8 fed on hot frozen thawed rodents.  The ninth neonate refused food for four months and then went through a third shed.  At this point it started feeding on live Anolis sagrei.  The 10th neonate refused all food for 8 months.  After the second shed it started feeding on live Anolis sagrei as well.

Collecting data from the newborn boas.
Corallus ruschenbergerii neonate, born 27 October, 2020.
C. ruschenbergerii unfertilized ovum, 14.25 g.
C. ruschenbergerii unfertilized ovum, opened shortly after parturition.
This Trinidad locale C. ruschenbergerii refused all food items for 8 months. After the second shed it started feeding on live Anolis sagrei.

Litters produced in captivity so far include:
10/27/2020  10 live/1 unfertilized ovum by J. Murray
11/14/2021  13 live by J. Murray
11/15/2021  12 live/1 stillborn by J. Murray

Behavior

Nocturnal in nature, arboreal in habit.  C. ruschenbergerii tend to loosely coil on a branch vs. tightly coil around it like several other species in the genus.  According to Mole and Urich these snakes sometimes lie in water, but only occasionally. They lie in the slender twigs at the furthest extremities of the thick branches of the tree partially screened by the leaves and are singularly inconspicuous. They note that the snakes are quick to bite when disturbed , a behavior many present day keepers of Corallus ruschenbergerii can attest to.

Corallus ruschenbergerii female, Trinidad locale.

Diet

Diet in the wild consists of squirrels, rats, opossums and bats.  Lizards as a prey item has  been documented on Trinidad (Henderson 1993, Murphy 1997).

Mole and Urich investigated the species on Trinidad and assume that probably their first meals consist of small lizards, such as Anolis alligator (=Anolis richardii), very young birds, mice, and rats. They note that as they grow, are soon able, to catch full-grown mice. They state that the porcupine rat Makalata didelphoides (in the article Loncheres guianae = syn) is its chief food .

Pizzato et. al described a difference in prey items from young to mature snakes from Lizards and Frogs to Birds and Mammals . Henderson and Pauers analyzed the stomach contents of various Corallus species and confirmed the shift from ectothermic to endothermic prey items . More recently in a C. ruschenbergerii from Colombia (132,6 SVL) an owl was found as a prey item, making this the first record of birds as prey for C. ruschenbergerii and the first record of a bird of prey for the genus Corallus .

Sexton and Heatwole analyzed the stomach contents of three captured C. ruschenbergerii in Panama (named Boa hortulana in their article). While two specimens had empty stomachs, the third contained the remnants of a gravid Basilicus basiliscus . Henderson reported four instances where bats were consumed by animals from Colombia, Costa Rica, Panama and Trinidad . Henderson and Boos analysed prey items from preserved museum specimens of C. ruschenbergeri. While they found that the diet of C. ruschenbergeri on Trinidad and Tobago is not, in basic composition, different from mainland populations (it includes birds, bats, and rodents), Corallus ruschenbergerii attains a greater size on Trinidad and Tobago and correspondingly, their diet includes larger prey items than elsewhere, with representatives of mammalian orders (Carnivora, Marsupialia) that are not represented in the mainland sample .

C. ruschernbergerii in captivity take an assortment of appropriately sized rodents (mice and rats) and fowl.  Newborn have fed on white fuzzy mice (fm), white small mice (sm), black sm,  and chick fuzz covered hot sm.  Some required anole scenting to voluntarily feed (Booth, pers comm).  Approximately half the litter took frozen thawed mice, with and without chick fuzz,  left in overnight (LIO) (pers. exper.)

Captive management and captive population

The Mangrove Treeboa is kept and bred by various institutions and private keepers worldwide.  However, very few animals with a confirmed origin of Trinidad in captivity.  We are aware of a colony of ten Boas (4.6 sub-adults and adults) in the possession of three  collectors in the USA.  They are currently collaborating on a scientific program to perform a genome study that will guide the development of a Species Survival Plan (SSP) and establishment of a stud book for this locale of insular treeboa.  They hope to include, if possible, the treeboas from Tobago and Isla de Margarita in the genome study at a future date.

One of the many variations of insular C. ruschenbergerii.

Conservation Status, threats and population size

CITES:  Appendix II
Trinidad and Tobago joined CITES on 19 Jan 1984; entry into force on 18 Apr 1984.

IUCN Red List:  Least Concern (LC)

The National Center for Biotechnology Information:  (click here)

CITES import/export data:  (click here)

The IUCN 20 July, 2015 rating of LC is described as follows:

Listed as Least Concern in view of the large range, large number of locations, apparently large population size, occurrence in several protected areas, and apparently stable trend.

The islands Trinidad and Tobago are relatively large in size. Trinidad has a surface are of 4830 km2 and Tobago 300 km2.  Wildlife protection laws are enforced and several nature reserves are present on the islands; the oldest nature reserve in the New World is located in Tobago.  Almost all of Tobago’s forests are designated as protected forests.  The first protected area, a game sanctuary, was created in 1928 .

Taylor et al. provided an analysis of the population densities of Corallus ruschenbergerii in the Caroni Swamp. Population studies that are conducted over a short time period often bear a large degree of uncertainty in the results. The authors were aware of this and conclude a cautious number of 11.022 Treeboas per square kilometre .  Auguste believes that the Caroni Swamp provides a relatively stable habitat for C. ruschenbergerii at this moment in time .

Tolson and Henderson list common threats for West Indian snakes :

  • Predation by introduced exotic mammals
  • Alterations in the prey base
  • Habitat destruction/alteration

The CIA World Factbook lists the following environmental threats for Trinidad and Tobago: water pollution from agricultural chemicals, industrial wastes, and raw sewage; widespread pollution of waterways and coastal areas; illegal dumping; deforestation; soil erosion; fisheries and wildlife depletion .

Provided below are maps to illustrate the extent of habitat destruction and alteration due to development and agriculture.

Trinidad
Tobago
Isla de Margarita
Early map of Trinidad, 1780.
Early map of Tobago, 1768.
Early map of Venezuela with Isla de Margarita, 1638.

On display in these Zoos:

Belarus Minsk (Zoo)

UK Lower Basildon (Beale Wildlife and Animalpark)

Czech Republic Horní Pěna (Zoopark Na Hrádečku)

Magnificent Mangrove Treeboas

More information

Through the authoritative academic work of Robert W. Henderson as well as others, a wealth of information about the natural history, habitat use and behavior of the Genus Corallus is present. Henderson summarized the current knowledge about the genus in three books dedicated to the genus Corallus . We strongly recommend the reading of these books to the dedicated Treeboa afficionado.

Citations