Giant snakes in captivity

The care and keeping of giant snakes is a contentious subject, particularly in the private sector. Not only do giant snakes require giant enclosures, but they also demand an immense amount of electricity and pose a genuine threat to human life. All these challenges can be overcome with the correct knowledge and resources but for most private keepers, these resources are well out of reach. Despite this, some species, such as reticulated pythons (Malayopython reticulatus), are frequently kept in the UK. Others, such as green anacondas (Eunectes murinus) are less commonly kept but still occupy myriad private collections across the country. Whilst there is no innate distinction between the resources available to a zoo and the resources available to a private keeper, zoos often have much more funding and a necessity to present only the best husbandry practices to ensure a positive visitor experience. In this sense, zoos offer excellent insight into how giant reptiles should be kept.

Anacondas at Paradise Wildlife Park

Paradise Wildlife Park in Broxbourne, Essex is home to Optimus, the UK’s largest on-display green anaconda. Optimus and recently introduced, Nina share one of the most renowned giant snake exhibits in the country. With a whopping 80 square-foot of floor space, including a 4-foot-deep pool, keepers at Paradise Wildlife Park have managed to house these goliaths in optimal conditions.

Green anacondas are the heaviest snakes on the planet. They have been the subject of various horror films and feature heavily in South American mythology. Reports of man-eating snakes are rife in pop culture and whilst unverified, are likely to have occurred in remote regions of the Amazon, where native children play close to the river. There are, therefore, many benefits to displaying these otherwise fear-inducing snakes. “Green anacondas have been kept in zoos and private collections for many years now” explains Jennifer Bartlett, Reptile Section Leader at Paradise Wildlife Park. “There is a challenge for us is that not a lot of research happens on their wild ecology. They are considered ‘least concern’ by the IUCN but listed as ‘data deficient’. The big problem is in South America, they’re very widespread and they live in environments that are very difficult to track in the wild. A lot of collections display green anacondas, but because they live such a long time and get so big, they are often rehomed to other collections once they reach a certain size. We’ve had Optimus from a private collection at a very young age and once she got to a certain size we hit that same crossroad. However, we chose to build something massive that would house her for the rest of her life.”

Green anacondas were previously ranched in South America quite often. Their distribution covers the entire Amazon region and as far South as Paraguay. As their distribution covers many countries, each with slightly different animal export laws, in-situ keepers could breed large numbers of the snakes and export them across the world to zoological collections and private collectors with relative ease. Nowadays, things have changed slightly and laws are more stringent. There are also four different species in the Eunectes genus, and more are likely to be described in the future.

Jennifer continued: “Anacondas are livebearers, they give birth to anything up to 30 babies in one go and because of that, most people that do breed them will struggle to house them all. Currently, there are no breeding programmes established for zoos, which isn’t a problem now but perhaps in 20/30 years we will find that there will be a shortage of green anacondas as display animals.” Green anacondas are also able to reproduce via facultative parthenogenically, which means females can reproduce by replicating themselves in the absence of a male. This was first recorded in the UK in 2014 by O’Shea et al but has more recently been documented in other collections across the world. So far, the parthenogenic births have only produced a small number of young (between three and five offspring) which is very few compared to a normal birth.

Creating paradise

Large constrictors, such as Burmese pythons (Python bivvitatus), boa constrictors (Boa constrictor) and to a lesser-extent African rock pythons (Python sebae) have historically been housed in proportionately small vivaria. Nowadays, particularly in the UK and Europe, that is changing. Although the popularity of Burmese pythons may have dropped, various social media platforms still show enormous, reticulated pythons (arguably the longest snakes in the world) kept in outrageously small enclosures. Although anacondas are never likely to reach the same commercial appeal as reticulated pythons, these worrying husbandry misconceptions may have far reaching implications.

“A lot of people underestimate the amount of space they need” added Jennifer. “We are firm believers that snakes should be able to fully stretch out. These snakes really do require their own building. Most private keepers can’t facilitate that, but there are some that can. Another major consideration is how powerful they are. Anacondas are typically quite docile, but they can be very unpredictable. You do need a second person in the room whenever you’re getting close to giant snakes. In our case, these are trained staff who know the procedure if the snake does bite.”

There are other obstacles when it comes to housing a giant snake. Whilst some of the larger pythons reach similar sizes to green anacondas, their natural behaviours make them slightly more manageable providing a suitable enclosure can be maintained. The building that houses Optimus and Nina cost the zoo around £250,000 to build. As well as all the necessary lighting and heating, catering to the species’ aquatic behaviours is not only costly but demands a lot of time and effort.

We know they spend about 80% of their time in the water but there are myths out there too” added Jennifer. “Some say that once they reach a certain age, they will spend all their time in the water and that just isn’t true. Although it is rare to see them completely out of the pool, our huge female, Optimus will happily sit on the land. We will often catch her on the cameras moving around. They spend most of the day in the water and then perhaps every other night, they will come out, follow scents and explore then return to the pool before the zoo opens the next morning. They definitely appear to feel more secure in the water. They are a lot more timid than people realise. They can be inquisitive but as soon as they notice anything unusual, they will move as far away from it as possible. If we go in at different times, or if we feed them later in the day, they will be much more hesitant to feed. This makes it even more rewarding when we do see them being active and curious”

Optimus the anaconda at Paradise Wildlife Park

Wild conditions

Green anacondas are perfectly adapted for a semi-aquatic lifestyle. Their eyes and nostrils are positioned slightly higher on their head to allow them to stalk their prey from beneath the water. They are primarily nocturnal and use flooded plains and forests to move long distances, undetected. This cryptic behaviour is extremely important to juvenile anacondas which are prey for a huge number of Amazonian species. “When we first moved Optimus in, you could tell she had never had a pool that was deeper than she was. It took her about three months to learn to swim. We added logs to make sure she felt secure, but you would see her latch onto the log with her tail. She would move around the pool but always gripping onto something with her tail. When we moved Nina in, she went to explore the pool and just instantly dropped in. So, she spent about 3 days gripping Optimus to make her feel secure while she was in there. Now she’s swimming great on her own.”

Allowing animals to enact their natural behaviours is the backbone of excellent husbandry. Over the years, a greater understanding of animal behaviours as well as new advancements in product design, have put a greater emphasis on welfare standards. Whilst it is possible to keep a whole plethora of animals alive and even breed them, good welfare standards require innovative enclosure design and technologies. Whilst the provision of UV lighting is now considered the industry standard for all reptiles and amphibians, providing this to a 15-foot snake can prove to be far more challenging (and a lot more expensive!)

“We have a 125kg sand filter with UV filtration and heating attached to the water supply. The enclosure itself has underfloor heating as well as backup heating. We can adjust this throughout the day so the heating moves around the exhibit over time to encourage more enclosure use. We have a misting system as well as a big UV lighting rig. This is supported by natural sunlight that comes through the back window, which helps with the day/night cycle. We cover all the basics but on a much bigger scale.”

Maintenance

As well as the initial financial output for establishing such a large exhibit, keepers at Paradise Wildlife Park have their work cut out when it comes to maintaining the species. Filters are cleaned once a week. The tank is back washed, and all urates and detritus are scrubbed away twice a week. The keepers do a full water change every three months. The substrate is spot cleaned constantly and a full substrate change happens each year. Safety is also a huge concern and the pool has been fitted with a duck valve, that allows the water to be drained very quickly. This is an important health and safety feature irrespective of whether the snake is in the exhibit.

Keepers practice de-sensitization techniques to get the snakes more familiar with the keepers. This is usually limited to touching the snakes with snake hooks as they walk past. Over time the keepers have managed to safely touch the snakes with gloves to get the animals more used to them. “Reptiles are very stoic animals” added Jenny. “When they’re more relaxed, they are more inclined to show you when they are unwell.” The keepers are much more hands-on with their reticulated pythons than their green anacondas. This is because they generally spend more time on land and have slightly more predictable temperaments than the anacondas.

The anacondas also have an off-show area for their exhibit which is comprised of an 8 feet long vivarium that acts as a temporary isolation area for the snakes. “If we have an animal that isn’t well, or we need to monitor their diet or separate them for any reason we have an area where we can do that. If we also need to do any major maintenance, they can come into this off-show vivarium temporarily while we get the work done. They will come into this area on their own as well, so they have an area off-display if they want to be on display.”

Feeding

Feeding giant snakes can also present an issue. In the wild, green anacondas are known to feed on other apex predators including caiman (Caiman crocodilus) and jaguars (Panthera onca). More frequently, they will feed on capybara (Hydrochoerus) which can grow up to 1.3m and weigh in at 60kg. In captivity, this is very difficult to replicate. Large-bodied prey also poses a genuine risk to the health of the snake. A wild snake must feed on whatever sized prey it can hunt. During this time, they are vulnerable, especially when feeding within the water. Digestion can take up to three weeks and the animal will not need to feed again for several months. Zoos often choose to mitigate some risk by feeding smaller prey, more often. “We feed them all frozen foods” explains Jennifer. “Whole, XL Chickens, rabbits, rats and quails tend to be our go-to. We feed them once every month or so but that depends on the amount and the size of the food they’ve had. When we first introduced Nina, we fed them both at the same time but in separate locations. When we strike feed, we only feed them in one spot, so they know ‘this is where I get fed’. We do also scatter feed, so we will make scent trails and leave prey items around, but it is more difficult to monitor that, especially with a new snake.”

Keeping giant snakes

Although giant snakes have been popular in herpetoculture since the exotics boom of the 1980s, people’s ideas on what constitutes ‘successful’ husbandry has changed over time. The limitations of resources, particularly in the private sector mean that keeping giant animals is often not viable. However, exhibiting these impressive reptiles can have serious conservation benefits.“It is so important to display these giant snakes” Jennifer added. “Not everyone can visit South America and see these animals in the wild, but a lot of people have seen horror films about these snakes. We want people to want to conserve them and not be terrified of these animals. It’s crucial to developing understanding. We used to do a lot of keeper talks pre-covid and the anacondas were one of the most popular. Allowing people to see them up close and see them swimming and enacting natural behaviours is so important.” While people remain fascinated by giant reptiles, they will always have an appeal to private keepers. It is therefore vitally important that a balance is struck between inspiring budding conservationists with educational outreach and providing the very best husbandry practices for these animals in captivity.”

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