Cohabiting Reptiles – Hot Topic

It’s a hot topic which is subject to some particularly heated debate. Should herps be housed on their own, or is cohabiting reptiles advisable? As with almost everything in life, there is no right or wrong answer. We spoke to a handful of respected herpers to find out what they think about cohabiting.

Dave Perry
Technical Director – Peregrine Livefoods
Cohabiting different species is a much debated topic, and one that seems to generate polarised views from keepers. Historically, the prevalent view is that cohabitation of different species is a total no-no that cannot work, and will inevitably lead to disaster. This view is changing now as the prevalence of large, naturalistic enclosures and the understanding of environmental conditions increases.

In the wild, reptiles will inevitably cohabit. They will also eat each other. This means cohabiting in captivity needs some careful consideration. A lot of thought must go into the construction of a cohabited enclosure. There is a lot to consider – cannibalism and disease transmission to stress from competition, optimum heating, lighting and shelter opportunities, along with the stresses of mating, aggressive feeders and other such competition. The wild is vast and animals have at least the opportunity to escape these issues to some degree, but the potential for these to become a problem is far more likely in a captive environment.

The knowledge necessary to mitigate these is something only an experienced keeper would possess. Species chosen to cohabit must be from the same environment and have similar needs, but also occupy slightly different niches in the environment to avoid excessive competition. For example, Anolis, Rough Green Snakes and Green Tree Frogs can be housed together and are spatially separated by both their slightly different environmental needs (bright basking zone vs thick foliage for example), and also their behaviour (nocturnal vs diurnal).

However, grouping simply by similar characteristics needs to be viewed with care. Mediterranean Tortoises and Green Iguanas are both herbivorous, but have totally incompatible environmental needs, so they would be unsuitable for cohabiting. One aspect that is becoming more important to keepers is the need for enrichment in captive reptiles. While nobody would suggest that housing predator and prey species together would be acceptable as a source of enrichment, contact with other, compatible, individuals certainly does provide stimulation. Indeed many reptiles are now known to live in colonies and even recognise individuals and family members, so contact is an enrichment event which many reptiles experience in the wild.

In summary; cohabiting certainly is possible and can be beneficial for animals and owners alike. But great care should be taken to ensure compatibility between species, and even individuals, and good enclosure design is vital.

Cohabiting Reptiles

Francis Cosquieri
Reptile keeper
I find that, as with so many aspects of this hobby, there are no absolutes. It is possible to cohabit snakes, I’ve done it all my life with many species. However, some species shouldn’t be cohabited and the first hurdle is knowing which species cohabit well and which might present problems. I have succeeded, and continue to succeed, cohabiting many different species and genera. While it can be done, it is not something that should be undertaken lightly and several things need to be borne in mind when doing it. That said, providing these basic guidelines are kept there should be no problems.

Firstly, and perhaps most obviously, the snakes should be species that don’t eat other snakes, although even this is malleable. Dione’s Rat Snakes are noted snake eaters that cohabit very well together, and I know several people that cohabit various King Snakes without problems despite the fact that Kings are notorious snake eaters. Most accidents seem to occur at feeding time or shortly afterwards. Presumably the snakes smell food on the other snake. Therefore it is always wise to feed cohabited snakes separately.

Next, they should be of similar size, healthy, settled, quarantined and taking food well. Even Corn Snakes can and will cannibalise other snakes – as was demonstrated in the photo taken by Tom Charlton of a Corn eating a baby King Cobra it was intended to be food for. This also extends to members of the same species.

Thirdly, the snakes need room. Most single adult Dione’s Rat Snakes, for example, reach about 24” and can be kept in a 24”x18”x16” terrarium; I keep pairs in 36”x24”x24” or 48”x18”x16” terraria. The more space, the better. There should be enough hides at both the cool end and the warm end for the snakes to be able to use either of them while keeping away from the other snake if it so desires. Interestingly, what you will usually find is that the snakes spend most of their time in contact with one another, especially when at rest.

Next, the genders of the snakes should be considered. For me, the absolute worst pairing is one male and one female. It can be done, but the problem with this particular pairing is that the male can be prone to chasing the female relentlessly which can cause her stress. If I am housing mixed genders together I always try to ensure there is at least 1.2 or even more females to ensure the male spreads his attention between the two. In this case, larger enclosures really are important.

For example, I used to house a 1.2 trio of Corn Snakes in a 48”x24”x48” terrarium that had three tall, vertical tree trunks. This gave the females plenty of scope to escape the unwanted attentions of the randy male when they wanted to and bask or hide in seclusion. Simply put, it isn’t healthy for a snake to continually be mated and produce multiple clutches a season. It places a large strain on a female’s body. While females can sometimes retain sperm and multiple-clutch of their own volition from a single mating, it isn’t something they should be subjected to by having a male constantly chasing them around trying to mate with them, and then having to bear clutches several times each year.

Related to this, juvenile or sub-adult snakes of mixed genders should never be mixed. I have witnessed first hand the stresses an early pregnancy can cause on a young snake’s body. As an example, I once accidentally housed male and female juvenile Dione’s Rat snakes together  which I thought were two females, and the male mated with the female. The female became gravid and laid eggs – and subsequently remained half the size of other females from the same clutch.

All of the energy that should have gone towards growth during her first year went to producing eggs instead. She is still tiny compared to her
clutch mates and will never reach full size.

Mixing two or more males or two or more females is easier but this can also cause issues. Many male snakes are territorial or will enter courtship rituals with other males. While this ‘wrestling’ is often harmless and neither party will go off food or show signs of stress, in certain species one male can and will dominate another kept in the same terrarium, so care must be taken. The male that is the loser in such interactions sometimes will become so stressed that he will not feed as regularly and his growth can suffer.

Many rat snakes perform this kind of dominance battle and I have seen it several times in Japanese Rat Snakes for example. Of course, keeping a snake singly makes it easier to keep track of how it is feeding, easier to isolate in case of potential illness, and is generally to be recommended for novice keepers. As time has gone by I tend to house snakes singly more out of convenience as I have a large collection and it is quicker to feed
them singly than if they are cohabited.

Those are some of the possible negative aspects of keeping snakes together, but there are positives too. The biggest of which is that, despite ‘common knowledge’ indicating that snakes are not social and do not react to one another, this is actually far from the case. Many species do socialise to varying extents to the point that, while keeping them alone probably does not have a negative impact, keeping them together could be considered another form of enrichment.

Psammophiine snakes for example take this socialisation further than people would think. They have narial valves beneath the eye which they use to mark out their territory by rubbing on landmarks, and also self-anoint by polishing their vents and flanks so that the pheromones rub off as they patrol their territories to delineate its boundaries. I have witnessed two different species of Psammophis ‘anointing’ other specimens kept together in this way. Further, at least some Psammophiine snakes take socialisation a step further. Pairs may bond for extended periods. Males capture prey which they present to females. Females seek out their male and squeeze beneathhim when threatened from above. Males will retain a territory and press-gang defeated rival males into becoming ‘vassals’ and helping him defend his territory and female from other interlopers. These behaviours are not the actions of asocial animals.

There is also the fact that snakes do in fact have various ways of signalling one another. These are sometimes subtle, sometimes not. I have watched Thrasops and Coelognathus ‘wave’ at one another from different vivaria across the room by performing anterior undulations, with the other animal responding. We simply do not know how much sociality affects these animals – not enough to appreciate that a lack of it could affect their husbandry in any way.

Ultimately, it is for each of us to decide whether to cohabit snakes. If it is done purely for financial reasons – keeping two snakes in an enclosure that is too small just to save on space, electricity or equipment – that cannot be recommended. But with a bit of thought and care cohabiting can provide an extra facet to these animals’ lives and offer many interesting insights to the observant keeper.

Gareth O’Dare
Senior Keeper – Newquay Zoo
I’d set up cohabiting enclosures of my own before I started at the zoo and was keen to bring this to my work when I started there. Additional motivation for cohabiting reptiles and amphibians came from the zoo’s directors who wanted to have more animals on display. However, these type of enclosures often attract criticism as people believe that housing two species together will require husbandry compromises for one or more of the animals. While this can often be the case, it is possible to get around these problems – particularly if you have the luxury of large enclosures as we do at the zoo.

Large enclosures enable us to create numerous microhabitats which allows different species to live alongside each other without coming into much contact. We also make sure we provide plenty of opportunities for animals to utilise the resources they need, including heat, light, shade, shelter, nesting and feeding opportunities. Competition and aggression are the most common issues in cohabited enclosures, but it’s not something we’ve seen in the large set-ups we have built.

One of my favourite cohabited enclosures is a paludarium containing Red Tailed Racers. I’d looked at the mangrove-swamp habitats these animals frequent in the wild and worked to recreate this as closely as possible. Although we pulled back on the idea of using brackish water, the tropical fish we have in the bottom of the enclosure are doing very well, and we often see them picking at the scales of the snakes as they lie submerged half in and half out of the water.

We have Red-Tailed Black Sharks, shoals of Black Ruby Barbs and Cherry Barbs and also Lace Gouramis. The tank is planted with Java Ferns and Java Moss and has artificial mangroves and a sand bank in one corner which hides our filtration equipment. We’ve even had Red Tailed Crabs in that enclosure too. It’s fascinating to watch the Racers explore and utilise the various levels of the enclosure.

The recent bioactive trend has seen cohabiting become more common. This isn’t only because keepers are experimenting with naturalistic setups with various reptiles and amphibians. Keeping invertebrate clean-up crew specimens in a tank with reptiles is still, literally, cohabiting. It’s great to see and will be a real attraction for keepers to observe. At the zoo we have to service both ends of the spectrum when it comes to keeping reptiles in captivity. We need to display exemplary animal husbandry, but we also have to engage the visitor in a way which keeps them entertained and informed. We have to do both things well, or we have failed. I’m pleased to say the cohabiting enclosures do a great job of ticking both of those boxes very well indeed.

Tariq Abou-Zahr
Exotics veterinarian
Cohabiting different species of reptiles and amphibians has always been a controversial subject. And rightly so, with many potential complications including aggression, predation and stress, all ultimately potentially leading to compromised animal welfare. Many species have different requirements in terms of husbandry, and even subtle differences between species that occur in a similar habitat naturally can mean it’s difficult to keep cohabited animals in optimal conditions.

From a veterinary point of view, there are also potential disease complications associated with keeping different species in the same enclosure. While there are many examples, a few include the following: Entamoeba invadens is a micro-organism which causes disease in reptiles. It can affect many species, including snakes, lizards and chelonia. Some can carry this parasite without showing clinical signs, while others become severely infected and may die as a result. Carnivorous reptiles tend to be far more susceptible, while herbivores rarely show signs of disease with Entamoeba. Tortoises may carry a heavy burden with no issues at all, but if those tortoises are kept with lizards or snakes, the tortoises can be asymptomatic carriers and act as a vehicle for severe disease in the cohabited species. Even among snake species, some North American colubrids show an inherent resilience to this micro-organism, while others may develop severe disease.

Arena virus is a pathogen of snakes thought to cause the neuro-respiratory condition called ‘inclusion body disease’ (IBD). It primarily affects boas and pythons. Some boas will show a very gradual disease process, while others will never show signs of disease but act as carriers or shedders. Pythons seem to be far more sensitive to infection with this virus, often deteriorating more suddenly and acutely. Given that most snakes are never tested for this virus, and that studies have shown that around a third of boa constrictors in the UK are carriers, if someone were to keep boas and pythons together there is a substantial risk of transmission and disease. This is a well-known example, but there are many other viruses that behave in a similar way. For example, Herpes virus is extremely common in tortoises. There are differences between species in terms of susceptibility to this virus, meaning that housing animals together could lead to the spread of this disease from one species to the other.

There are a small number of situations where cohabitation causes few problems and is not detrimental to the welfare, but it is only recommended for very experienced keepers who have researched the possible problems in detail and taken all steps possible to alleviate the risks. Keepers considering cohabiting reptiles should ideally have a discussion with their exotic animal veterinary surgeon about the risks of disease and parasitic transmission. Testing for these risks is also a good idea.

Eleanor Tirtasana Chubb
Tortoise Welfare UK
There’s so much room for error, particularly when you’re dealing with larger animals. You’ll often see tortoises being kept with other animals, but rarely is this done well. The problem is often down to the amount of faeces being produced from the animals above, which will inevitably fall to the ground where the tortoises live. This is how disease is transferred. In all but the most enormous enclosures you’ll certainly experience this problem.

You’ll often hear that it’s okay to house species from the same geographical area together, but even this isn’t a fool proof method. Arboreal snakes from Madagascar can require much more humidity than tortoises from that region, and so, housing these together will eventually create issues. Similarly, keeping birds with tortoises from the same region will inevitably result in disease transmission as bird faeces gets into the tortoises’ habitat.

On a slightly different note, it is also important for stores to consider the message they are sending to their customers, most of whom will be beginners or novices. All advice is open to interpretation and taken out of context. It would be quite easy for stores to find themselves subject to a backlash should their advice about cohabiting be misconstrued. It’s certainly worth being very careful about what you say and to whom.

In short, cohabiting is possible under some very specific circumstances. But the risks are great and it’s not something I’d recommend for fear it might be done badly.

Stuart Worth
Livestock Purchasing –Peregrine Livefoods
There’s no getting away from the fact that cohabiting reptiles and amphibians is difficult, largely because there are no hard and fast rules. Even when we look at traditionally compatriot species, such as Anolis and Green Tree Frogs – it only takes one big bully male Anolis and all hell breaks loose and the health of the other specimens can suffer. Cohabiting requires constant and careful observation. I guess that’s the reason cohabiting is largely frowned upon – because it can so easily go wrong. However, that’s not to say it can’t be done well, although this is usually only true when the keeper knows what they’re doing and knows what to look for. The first few weeks of cohabiting are the most crucial and it is during this period when most problems will occur, if they are going to. Aggression is almost always the issue.

One potential problem which could easily be overlooked pertains to the use of livefood. In some cases of cohabitation the size of livefoods required by the different species can vary. If larger livefood items are left uneaten they might soon grow to be large enough to predate upon the smaller cohabiting species. Again, care and vigilance is required in order to avoid problems such as this.

Chris Jones
Sales & Marketing Director – Peregrine Livefoods
For me, cohabiting must have a reason and benefit. When I walk into a store and see a Bearded Dragon kept with a Horsfield Tortoise because they don’t have the space, I get immensely frustrated.

However, reptile stores do need to appeal to multiple markets and for me, the bioactive trend has allowed us to attract the market similar to that of the advanced marine or tropical fishkeeper. These typically spend a great deal of time and money creating incredible displays which contain multiple species. If we look past reptiles and consider the amphibians and invertebrates too; we can make wonderful displays with multiple species that can and do cohabit in the wild.

A good example is our 6ft x 3ft display tank in the reception area at Peregrine HQ. We house a trio of Saban Anoles Anolis sabanus, several Blue Dart Frogs Dendrobates azureus, Red Eye Tree Frogs Agalychnis callidryas, Fire Millipedes Aphistogoniulus corallipes, several Isopod species and worms. Not all of these animals come from the same location in the wild, but from the top tier to lowest section of the terrarium we are providing suitable conditions for all of these species. Having a mix of diurnal and nocturnal works nicely and allows for a hive of activity to be seen at any time of the day or night. Every time I walk past this terrarium I have to stop and check it out. You just don’t get that with a typical single-species environment.

To summarise my point, most common species shouldn’t be kept together for multiple reasons as already discussed in this article, but as a specialist reptile store you should have the knowledge and experience to provide a good quality environment to allow for cohabitation. If you’re putting something like this on display in your own store, it can only have a positive impact and introduce new keepers into the hobby.

Cohabiting Reptiles – Hot Topic

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