We are still on Principe and down to the hard corps: me, Wes and Josef. The mushroom and plant folks, Dennis, Brian, Tom and Rebecca are home in San Francisco by now. So it is time to tell you a little about my own research interests. Cobra Jita is a snake and we have been looking for it all week; in order to explain why, I need to tell you a frog story.
Josef Uyeda on Principe. Weckerphoto GGIII
As I have said, the fact that there are amphibians here at all is astounding; amphibians, along with primary freshwater fish, are among the poorest dispersers across saltwater barriers known. They are the last kinds of critters one would expect to find on an oceanic island…. Think of the Hawaiian Islands and the Galapagos, perhaps the two most intensely studied oceanic archipelagos in the world… no frogs or other amphibians, right? But here on Sao Tome and Principe we have seven amphibian species, one of which is the famous caecilian, Schistometopum thomense. How can this be? How did they get here? More on this later, but one of the keys is time: remember that Sao Tome is at least 15 million years old, and Principe is more than double that, perhaps 31 million years. Hawaii and the Galapagos are but 5 million years max.
During GG I, we collected series of little brown frogs of the genus Phrynobatrachus from various locations on both islands; at the time all of them were considered the same species, P. dispar, originally described from Principe over 100 years ago. In 2005, a bright young intern from Willamette University named Josef Uyeda, spent the summer in my lab studying these preserved specimens and concluded that the frogs were quite different. Josef joined GG II and did a lot of collecting on both islands, recorded calls, did dissections and comparisons of DNA from the critters on both islands. The results are that the two island frogs are VERY different; in fact, there is nearly 21% DNA sequence difference between the two; indicating that they have not interbred in many millions of years, possibly predating the existence of Sao Tome (yet they still look virtually identical!). Moreover the two together appear to be more closely related to East African species than to more nearby West African species, but more on that later. In 2007, Josef, I and Breda Zimkus of Harvard described the Sao Tome brown frogs as a new species, Phrynobatrachus leveleve.
Phrynobatrachus leveleve. Sao Tome. Weckerphoto GGIII
Phrynobatrachus dispar Principe. Weckerphoto GGIII
from Uyeda et al. 2007. Proc. Calif. Acad. Sci. 58
This brings me to cobra jita (pronounced “zheetah” – it means snake slow, as opposed to the other Principe snake, cobra sua sua, which means snake fast!). Here we have the same situation as we had with the small brown frogs, Phrynobatrachus. Jita (more properly known as Lamprophis lineatus bedriagae, or lined house snake) has always been considered to be the same species on both islands. After our frog studies, I am not so sure! They look different – regrettably I will have to post a picture of the Sao Tome form later… didn’t bring one in my zip drive—the Principe form is much more obviously patterned than the Sao Tome snake. During GG I and GG II we got very good samples of the Sao Tome population, but for some reason, only one specimen from Principe.
Lamprophis from Bombom Id, Principe. Weckerphoto GGIII
Lamprophis from Sao Tome. D. Lin photo. GGII
Josef is now a PhD candidate at Oregon State University and joined us a couple of weeks ago in our search for Jita (among other things I will describe later). Snakes, as you probably know, are where you find them… as primary predators, they are never very common but always around, and such has been the case here on Principe. It has taken us six days of trekking around in the forest, turning over logs, etc. to find six snakes. But I am delighted. This is certainly enough now to estimate the genetic distance between the two populations, and given the age of these islands, I will not be surprised at all to learn that they are distinct at the species level.
Josef and I looking for Jita on Bombom Id. Weckerphoto. GGIII
We have learned a lot about this critter. On Sao Tome, Jita is primarily nocturnal while the daylight hours on that island seem to be dominated by the endemic Sao Tome green bush snake, Philothamnus thomensis. This is the situation we would predict using island biogeographic theory—no niche overlap – they both seem to eat frogs and skinks, but at different times. But here on Principe, all of the jitas we have caught have been during the daylight hours, as was the single individual caught during GG II in 2006. Moreover, the green snake of Principe (yes there is a green sua sua here as well, but not related to the Sao Tome species) also seems to be diurnal! They are incredibly fast; we have seen two of them and missed both. So until we can look at stomach contents, we seem to have an ecological mystery.
Me, Josef and Ramos on Bombom Id. Weckerphoto GGIII
Our search has been greatly aided by an amazingly bright local naturalist; Jose Ramos Maria Vital Pires, or Ramos for short. Ramos has led us around this island searching for the elusive jita we have been blown away by his keen perception and observations of the local flora and fauna, and his delightful smile and sense of humor. The thing is everyone knows about this snake, most of the locals are to say the least, not exactly fond of snakes and one referred to as a “house snake” frequently comes a little too close for comfort, as you might imagine. But finding a snake when you are looking for it is entirely different matter. Our first success occurred on Bom Bom Island (not really and island, but sort of). I had just commented that the area Ramos was leading us through was too steep to find a snake, when he began excitedly shouting “snake!” only meters away. Within moments we had bagged our first jita.
There have been some rather ignominious moments for me personally. My two young compadres, Wes and Josef are willing to give me credit for catching but one jita, a dead one. The specimen had, in fact, been killed two hours earlier by a local woman who was delighted to have us remove it from along the road. This morning was the last straw. We had been combing Bom Bom Island again; Josef and Wes had taken a lower route than I and about an hour in, I heard Josef yell that they had caught a snake in the act of ripping a tail off a skink. Well and good, I thought, but where’s mine? So I am walking along, seeing snake food like skinks all over the place, when Wes and Josef come down the trail towards me. We stopped, admired the snake Josef had already bagged and the photos Wes took of it eating its skink tail, all three of us turned around…Josef stooped over and grabbed our largest jita of the expedition, about a foot behind me. I must have stepped right over it a moment beforehand. Perhaps it is not necessary to tell you that there has been much snickering among the younger members of this outfit ever since… Argh.
Josef collecting a jita on Bombom. Weckerphoto GGIII
Nova Cuba, near Santo Antonio, Principe. Weckerphoto GGIII
PARTNERS We gratefully acknowledge the support of the Research Investment 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/ and especially the generosity of three private individuals, George F. Breed, Gerry F. Ohrstrom and Timothy M. Muller, for making GG III possible. More anon.