Over the last several months I have been reading websites, magazine articles, and other forum posts discussing various biological and taxonomic aspects of the least known species of the anaconda complex, Eunectes beniensis. I guess my main concern is the large amount of erroneous information that is being passed around with regards to this relatively new species. I would like to try and clarify some of the mystery out there about this species and hopefully correct some of this misinformation.



Lutz Dirksen was the first individual to notice a different type of anaconda in the floodplain areas of northeastern Bolivia in 1994. This species was later described by Dirksen and officially recognized as a new species in 2002. The species name is derived from the State of Beni in the country of Bolivia. It is named so as Beni was the location of the discovery of the holotype specimen, or the original specimen from which a new species is described. E. beniensis was originally thought to be a possible hybrid between E. murinus and E. notaeus, but closer study showed that this was not the case. While the ranges of E. murinus and E. notaeus do overlap in some areas, there have be no specifically identified specimens showing intermediate traits captured in these areas. Additionally, while the northern geographical range of E. beniensis does slightly overlap that of E. murinis, no range overlap is known to occur between E. beniensis and E. notaeus.



One major misconception that occurs with E. beniensis is in regards to the size of this species. I have seen numerous references in magazine articles and internet sites stating the average length at 4 to 5 feet. I am not sure where the data for this comes from, but I have not seen anything in the scientific literature to support it. Just looking at the Type Series alone, which is represented by 3 sub-adult to adult male specimens, the average male in just this small group is between 6 and 7 feet. The one female included in the Type Series measured 10.5 feet. Having spent a fair amount of time researching sources of information on E. beniensis, I have come across a dozen or so photographs of captured specimens in the field. All are being held by people, all full body photos, and therefore relatively easy for length estimates. Most appear to be in the 6 to 8 feet range with a few in the 8 to 10 feet range. There are a couple that appear to be easily 10 to 12 feet. Dirksen estimates from all of the data he has gathered that female E. beniensis probably reach 13 to 14 feet, and goes on to say, possibly longer. With several 10 to 12 foot individuals in just a handful of known specimens, I would not be surprised at all if really large female E. beniensis hit the 15 feet mark. This makes E. beniensis the second largest of the 4 species of anaconda, surpassing E. notaeus and E. deschauenseei in average length.



Most of the information I have gathered comes from papers written by Lutz Dirksen and Wolfgang Bohme, and these two gentlemen have added immensely to the body of knowledge with respect to all of the anaconda species, but especially E. beniensis.



Kelly

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