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Gulf of Guinea Expeditions 

April 29, 2009

The Race: Within the House of Slytherin (II. some snakes)

Snakes are not great over-ocean dispersers; they are certainly better than frogs or freshwater fish but not as successful as spiders, geckos and skinks. For instance there are no native snakes in the Hawaiian Islands although they do occur in the Galapagos, but these are much closer to a source continent. In spite of their small size and isolated nature, and Príncipe have a rather surprising snake fauna; there are at least seven species, five of which we know to be endemic – they are found nowhere else. This group includes three species of “lower snakes” or scolecophidians; these are small, blind burrowing forms, two of which are endemic to São Tomé and one to Príncipe.

Rhinotyphlops newtonii, a burrowing scolecophidian from Sao Tome. (D. Lin phot. GG I)

The more advanced snakes (caenophidians) are represented by one endemic, diurnal (daytime) species on each island (belonging to two unrelated genera) and a nocturnal subspecies which is currently thought to be the same on both islands.

Hapsidophrys principis- (cobra sua sua:“snake fast”)- the endemic diurnal  species of Principe (D. Lin phot. GGI).

The nocturnal snakes are known as cobra jita (“snake slow”). I have mentioned these in earlier blogs, and my suspicions are that the two island populations are distinct endemics—we are beginning a molecular study this summer to test this hypothesis.

Cobra jita (“snake slow”), the nocturnal species from both islands?  (Weckerphoto. GG III)

But here I want to talk about the remaining snake found on São Tomé which the islanders call cobra preta (“snake black”); this is the only dangerous species on the islands, and it is a bit of a mystery to me.

The black and white, or Forest cobra – Naja melanoleuca. Ethnobiomed phot.

Widely distributed on the African mainland, this species is known as the forest cobra, or black and white cobra (Naja melanoleuca), and it is quite a venomous and formidable animal. In some parts of its range it can exceed 3 meters in length (10’).

Forest cobra distribution.  map by Nils Boyson

Head of Forest or Black and White cobra, Naja melanoleuca.

This snake, like most true cobras, displays a hood as part of its defense system, essentially making itself look larger in order to warn of its presence. Like all members of family Elapidae, cobra preta has erect front fangs that are hollow and syringe-like, and it injects prey animals with venom that attacks the nervous system (neurotoxin).

[l.]  C. melanoleuca fang showing aperture (Bruce Young) [r.] direction of venom injection (E. Jose)

All of the São Toméans know of cobra preta and fear it, although I have no idea how frequently citizens are bitten. Based on a dead-on the-road specimen at nearly sea level in the south of the island, we know it occurs in lowlands, but I suspect it is more common in the mid-level forests; during GG I, we purchased a number of skins from farmers at Bombaim, which is at middle elevation.

Dead on the road, south Sao Tome. (RCD phot. GG recon 2000)

Joel Ledford with Bom Sucesso specimen. (J. Ledford phot. GG I)

The 2- meter specimen above was killed by locals near the Botanic Gardens and Herbarium of Bom Sucesso at about 1000 m, and we were able collect it during the GG I expedition.

During GG II in 2006, we encountered a very large specimen while collecting along an aquaduct in the Contador Valley on the west side of the island at 700 m; in fact, several of us nearly stepped on it before we were aware of its presence.

On our most recent foray, GG III A, we were again on the Contador Aquaduct when a middle-sized snake was killed by locals around a bend in the road, less than 100 m from where we were working.

Contador Valley specimen (Weckerphoto GG III)

Regrettably, they had beheaded the specimen, and so it was of no value as a voucher specimen; however, we were able to photo-document the animal and I removed some liver tissue for future analysis.

Liver tissue removal. (Weckerphoto. GG III)

The presence of the cobra on São Tomé Island is widely considered to be the result of human introduction, most likely accidental (it is hard to imagine an individual bringing a deadly snake on purpose!). Physically it appears to be identical to the widespread Naja melanoleuca of the mainland. Accidental introduction makes ecological sense to me as well because the species does not really fit into this old ecosystem as we are beginning to understand it. We know that the other higher snakes feed on endemic prey species such as frogs and lizards. But aside from some birds, there do not seem to be endemic prey species that are of sufficient size to sustain a large, heavy-bodied snake like cobra preta; on the other hand, plenty of rats, chickens, etc. have been brought over by humans since the 15th Century.

Two of the top African cobra experts are Drs Wolfang Wuster of the University of Wales and Donald Broadley of Zimbabwe. They are currently working on this species, and we have been sending them our tissue samples for DNA analysis. Soon, we should know whether or not this large cobra drifted out to the islands on its own and has since been genetically diverging, or whether it was brought to the island through human agency. Wuster and Broadley are currently describing a new species from Ghana that was long thought to be the species Naja melanoleuca.

Our parting shot:

Roadside enterprise on Principe(Weckerphoto GGIII)

PARTNERS

We gratefully acknowledge the support of the G. Lindsay Field Research Fund, Hagey Research Venture Fund of the California Academy of Sciences, the Société de Conservation et Développement (SCD) for logistics, ground transportation and lodging, STePUP of Sao Tome http://www.stepup.st/, Arlindo de Ceita Carvalho, Director General, and Victor Bomfim, Salvador Sousa Pontes and Danilo Bardero of the Ministry of Environment, Republic of São Tomé and Príncipe for permission to export specimens for study, and the continued support of Bastien Loloumb of Monte Pico and Faustino Oliviera, Director of the botanical garden at Bom Sucesso. Special thanks for the generosity of private individuals, George F. Breed, Gerry F. Ohrstrom, Timothy M. Muller, Mrs. W. H. V. Brooke and Mr. and Mrs. Michael Murakami for helping make these expeditions possible.


Filed under: Uncategorized — bob @ 12:02 pm

7 Comments »

  1. Dr. Drewes,
    I just read the spring issue of LIVE, and noticed you were interested in ideas about creating ways to communicate the biological uniqueness to the citizens of Sao Tome and Principe. I am a retired high school teacher from Tomales with experience in developing enviromental science curriculum, and would like to talk to you about how to involve local high school students in ways that might fit your needs. I can send you a VITA, or you can contact me if you are interested.
    Thanks.

    Comment by Bill McMillon — June 6, 2009 @ 6:20 pm

  2. Are cobras ever eaten as bush meat? I don’t suppose there are snake charmers there? Brown snakes get to oceanic islands in wheel-wells and cargo on planes. Most likely came as small juveniles with agricultural cargo.

    Comment by B. B. Gonzalez — July 11, 2009 @ 10:15 am

  3. So far as I know, none of the islanders eat cobras.. in fact, they fear them greatly.
    We will know soon enough whether the species is native to the islands. There is a rumor
    that they were brought intentionally to eat rats on the cacao plantations, but that seems
    pretty far-fetched to me.

    Comment by bob — August 18, 2009 @ 4:31 pm

  4. I will always remember fondly the Q & A session after you gave a staff lecture about hunting frogs w/ Jens in Africa. A woman asked with great concern, “Don’t you have to worry about snakes?!?” Your response – “But I *WANT* to find snakes!” I really liked that.

    Fifteen years later, I have my own 9 year old budding herpetologist – a girl who just loves frogs. The best thing in the new CAS, as far as she is concerned.

    Comment by Lisa Sebastian — August 19, 2009 @ 2:06 pm

  5. Hi, BB. somehow missed your comment. No so far as I know bushmeat on the islands is largely comprised of the non-native Mona monkeys and fruit bats. No, no snake charmers. I heard recently that the cobra was brought intentionally to control rats in the cacao plantations, but given the availablity of non-venomous snakes on the mainland, I find this unlikely.

    Comment by bob — February 8, 2010 @ 4:01 pm

  6. Thank you for the information on the “cobra preta”. We are missionaries on Sao Tome island, and have been curious about it for quite some time.
    Concerning the story about the “cobra preta” being brought over to kill rats, the story as told locally is that snakes were brought because of the rat problem, and the “cobra preta” was unknowingly mixed in with the other snakes. Because of its aggressive nature it eventually killed off the other snakes. Another load of snakes was brought in, purportedly to take care of the “cobra preta” and this load included the “jita”.
    It is said that when the two encounter one another the “jita” will kill the “cobra preta”. Of course there are local lores as to the reason behind this as well boiling down to a trick from the “cobra preta” getting the “jita” to change skins with him, when the “jita” realized the trick it tried to get its skin back and has since been angry with the “cobra preta” and kills it whenever they meet face to face in a perpetual attempt to recover its lost skin.
    Of course these are just local histories/stories told and as for their validity I cannot say, but they hold an important aspect of the peoples perspective, and culture.

    Comment by Doug Claypool — December 11, 2010 @ 7:27 am

  7. Doug,
    Thanks for your message. I am surprised we have not met! Where are you on the island?… As I have said in my blog , the scientific “jury” is still out with respect to whether or not “cobra preta” is naturally occurring or was brought by man; genetically speaking, this is not a difficult question; our colleagues who have our tissues just haven’t done it yet. While I have spent too much time in Africa to discount local legend “out of hand,” there are several holes in the narrative with regard to jita. First, as you have seen, we know from genetic data that the level of difference between ST and P jitas and between them and their mainland relatives is too great. This level of genetic differentiation (speciation) requires time in isolation, and this suggests to us that jitas have been on the islands since long before any humans were.
    I love the “skin” story.. I had not heard it… It reminds me a little of the cobra bobo legends. But frankly, I have spent the last 40 years working on African reptiles and amphibians and, having handled both kinds of snakes (jita’s relatives and preta) on the mainland as well as the islands, I can state with some confidence that there is no way a jita could kill a preta… the reverse is likely true… Jita has no venom, and moreover, as adults they are less than half the length and certainly only a fraction of the mass of an adult preta. What is interesting to me is what preta actually eats… I sincerely hope it is rats…. Again, thanks for your fascinating comments.

    Comment by bob — December 11, 2010 @ 12:26 pm

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