Reptile & Amphibian Forums

I am just looking for some facts/opinions/pics. it seems impossible to get reliable information on the adult size of male greens. I have spent countless hours checking zoo/breeder/forum websites and came away more confused... I've seen max size listed from 6' all the way to 15'(this sounds like an anaconda with a gender identity crisis, lol) any info would help, especially from anyone who has males in excess of 5 years of age. thanks!
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Heather J. Martin
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1 Solomon island ground boa, female
1 Green iguana, male
1 Ball python, gender unknown
1 Green anaconda, juvenile, gender unknown
1 Burmese python, 9', female

I am not surprised at what you have found with your searches, as there are many misconceptions about the sizes of male, as well as female green anacondas.

Dirksen says he has measured about 100 males with the largest being about 10 feet. The largest field study was conducted in Venezuela and was undertaken by Rivas. He collected several hundred males over a seven year period. He found that the average adult male green was between 7.5 and 9 feet. The largest male captured during the study period was 11 feet, 2 inches and weighed about 40 pounds. It must also be noted that these were all from the Llanos habitat of Venezuela and from the northern population, or Orinoco basin. There is some reason to believe that individuals from this population and habitat are slightly smaller than those from the southern population and riverine habitats in the Amazon basin. Large Amazon basin males have reportedly been seen in the 12 foot range. There are several people that claim to have seen or own males over 13 feet, but solid evidence as never been provided. I am personally not aware of any male green, captive or wild caught, that has actually been accurately taped at over 13 feet.

The outstanding male that Jud McClanahan owns that has been used in all of our successful breedings is a classic example of a mature, large adult male green. This male is almost 16 years old and is right at about 12.5 feet, and 70 to 75 pounds. He has not been overfed and is solid, but not overweight. There is no way to prove it, but going by his head coloration, I would guess that one or both of his parents were of Amazon basin origins. I currently have one of his sons that is 5 years old and 9.5 feet. He also has never been powerfed, but has been fed consistently. At this age and above, males are growing at an extremely slow rate. Hopefully this answered a few of your question. Please let me know if you need any additional information. Thanks,

Kelly

This was helpful, thanks. I have seen many cable tv documentaries that feature Rivas' work, but the shows never gave hard data. I am looking forward to getting my hands on the entire text of his study, I'm not sure if he has published it yet, I think it's still a work in progress. From photos I've seen, it appears that the males seem to somewhat less bulky than females of the same length, as well. One question, you mentioned the red stripes behind the eyes, I've heard that greens with this color might be from certain geographic regions, any thoughts on that? My little green has yellowish-orange stripes, and I've also seen photos of animals where the stripe was identical to background body color. I know that generations of captive breeding interfere with identifying a snakes origin purely by pattern, but it's a neat idea regardless. I need to do some more searching, but I remember hearing as well that some of the largest greens ever found were near the Peru/Colombia border.
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Heather J. Martin
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1 Solomon island ground boa, female
1 Green iguana, male
1 Ball python, gender unknown
1 Green anaconda, juvenile, gender unknown
1 Burmese python, 9', female

Rivas’s work is definitely worth the read if you are truly interested in the natural history of green anacondas. The study was published as his Ph.D. dissertation at the University of Tennessee and was submitted in May of 2000. It is about 300 pages and is by far the most extensive study I have ever seen conducted on a large constrictor species. Dirksen has also done much work with anacondas and published a book on them a few years ago. Unfortunately, it has yet to be translated into english.

You are correct in that male greens are much lighter in build than females, but from my experience it does not become really apparent until their second or third year. This is mainly due to the fact that the males and females are growing at a similar rate in the beginning, and the females are not adding much additional mass over the first couple of years. It has been found that the sexual size dimorphism with Eunectes murinus is one of the largest of all vertebrates. As you stated, there have been some larger than average females found in the southern Colombian, and northern Peru area. The rivers in this area are all part of the Amazon River basin. The southern areas of the Amazon Basin in Brazil, has also produced some large female greens as well. The highly suspect, long standing record green was taken on the Meta River in western Colombia in the late 1930’s. The reported 37.5 feet measurement is generally no longer accepted as several of the facts in the story cannot be confirmed. From the available information, it is now widely thought that this female was actually in the 25 to 26 foot range.

As far as captive breeding affecting pattern expression in snakes, I agree that this is quite true with snakes that are commonly bred in captivity. However, with green anacondas, captive breeding is so rare at this point that it has not become much of a problem with them yet (excluding murinus X notaeus intergrades). Additionally, from personal communication with venders, it appears that at least 95% of all greens advertised as captive born are actually produced from gravid, wild caught females. In these cases, the genetic integrity of the young is obviously still intact. The ocular stripe coloration you speak of is a debated concept by many, but I have looked at probably close to a hundred photos of greens from know localities, and have noticed that the greens from the northern parts of the range, of the Orinoco River basin, almost always have the clear, bright yellow or orange ocular stripe typically well outlined in black. Specimens from the southern part of the range, mainly the Amazon River basin, shown an ocular stripe as either faintly orange and highly diffused with the background color, or composed almost entirely of the background color. Many times these are also missing all or part of the upper black outline marking. While ocular stripe coloration is probably not 100% accurate as far as geographic origin, I believe it to be a strong indicator.

I have attached below a couple of photos of adult female greens I currently have in my collection. The upper photo is of a 15 foot female that showns the orange ocular stripe of an older (10 years) mature female. The lower photo is of a younger (5 years) about 13 foot female, and shows the type of ocular stripe which is composed entirely of the background coloration. Both of this younger females parents showed the same background coloration of the ocular. Also, if you can, I would be interested to see a head photo of your young green. Thanks,

Kelly

kelly, thanks for the detailed information, it really does help. I am always excited to learn something new about anacondas, however small or technical. Something that really caught my eye was that the majority of 'captive born' juveniles come from wild caught females. This was quite a suprise to me as I believed the exact opposite, nearly every advertisement I have ever seen stated that the baby anacondas being offered were 'captive bred/captive born'. The juvenile green I have now was presented as such, as well as a baby yellow I purchased years ago. Definitely something for me to ponder the next time I look at the classifieds.

Your info about geographic origin and the ocular stripe was very useful, as well as the pictures of the two females. My green has a stripe that is fairly well defined, I don't think any background color shows through any part of it. I have seen many pictures of captive anacondas and noticed one other pattern variation, I have no idea if it has anything to do with geographic origin. The big black dots on the back in some animals are nearly solid, on others, significant amounts of background color show through, making the spots look 'washed out'. This diffused color was very evident on my yellow anaconda, as well. And, the dots on my green seem to form two rows down the back, some of them almost touch, and there are a lot of them. In contrast, I have seen pictures of greens with fewer numbers of larger dots, spaced well apart. I will definitely put up a picture of my green, as soon as I figure out how...I'm still living in the 35mm age and haven't gotten my first digital camera yet. I love this forum and am so glad I found it, I will be here quite often.
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Heather J. Martin
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1 Solomon island ground boa, female
1 Green iguana, male
1 Ball python, gender unknown
1 Green anaconda, juvenile, gender unknown
1 Burmese python, 9', female

I have for many years, e-mailed most of the venders of newborn greens with questions about the production of the young greens they have for sale. For the last decade, I have been gathering data on newborn greens offered for sale to try and put together a better picture of their reproduction in captivity. I am interested in sizes and ages of adults, months of breeding activity, estimated gestation period, litter size, metrics on young, etc. The vast majority of vendors ended up telling me they didn’t have most of this information because the young were either born in South America from captive held females, or the wild caught female was imported as gravid and the young were born here in the U.S. Some even told me that they didn’t know where they came from but were pretty sure they were captive born. Either way, the venders all said they still considered them captive born. The key when buying captive born greens, or any other snake rarely produced in captivity, is to ask for photos of the adult breeders, breeding activity, or the young with the female right after birth. This is not asking a lot because many of the more well known breeders are already doing this. Yellow anacondas are much more readily bred in captivity and therefore are very rarely imported.

That’s a good observation about the spot pattern on the backs of greens. Other researchers have noticed this as well and have studied these pattern variations. Strimple, Holmstrom, and Henderson have looked into this extensively and found that there is no geographical range correlation to these patterns. They frequently found a full spectrum of spot shade variations within the same local population of greens, and sometimes even within the same litter of young. I believe the number of spots on an individual to be of similar circumstance as well. I know what you mean with the 35mm. I used one for many years before recently getting a digital. Thanks,

Kelly