Cohabitation isn't as evil as so many people(Americans from what I've mostly seen) make it out to be. That's how many keepers do it where I'm from and as long as you have spare enclosures to put animals in if they start squabbling it's very well worth it to try. Communal tanks are interesting to observe.
I’m going to assume you’re addressing the issue of cohabitating reptiles since with arachnids it’s a huge risk (in that case, cohabitation = communal up to the point where they aren’t). But I’ll try to discuss this with you.
I wouldn’t say it’s evil - more so it’s not recommended and frowned upon in most of the reptile community. There are sound reasons not to cohabitate, and the cons far outweigh the pros. I’ve seen some very nice zoos (e.g. San Diego Zoo) cohabitate same and/or different species of reptiles too, but just because they do it doesn’t mean it’s correct or safe. For example, I saw two green anacondas housed together along with two plumed basilisks. Doesn’t seem so safe for the little lizards, now does it?
If you don’t mind graphic pictures, I’d check out this leopard gecko care sheet (here), this thread on cagemate cannibalism in snakes (here, here, and here), and a study done with cottonmouth snakes (here, referenced here). Let’s also not forget the bearded dragon cannibalism picture either (here). This is what can go wrong, and it can happen quick enough you won’t be able to stop it even if you have good reflexes. Why would you put your animals at risk? It’d be similar to locking two roommates inside a confined area for long periods of time - they’d get pretty annoyed at each other eventually, and fights will happen.
If you have the spare enclosures in the first place, why wouldn’t you house the animals separately? Would you rather put your animals in harm’s way to prioritize seeing them “interact communally?” That’s a bit selfish.
In addition, diseases can be transmitted easily between cagemates - so instead of having to treat one snake for a RI, you’ll have to treat two or more because you’ll never be sure who’s healthy or not. It’s seriously similar to living in the dorms, if you look at it from the human perspective.
Also, how are you going to feed each cagemate equally, assuming they are not snakes (excluding insectivorous snakes)? With geckos, I mean you can tong feed them individually…but how long are you going to keep that up? There will be competition for food, and it’s going to be extremely difficult to prevent that.
Plus, you probably know that housing breeding pairs together long-term is very, very, very bad. Constant breeding exerts a massive toll on both parties, but the females’ health will take a huge toll. Vitamin deficiencies, drastic weight loss, increased food intake, etc…it’s like us getting constantly pregnant. Definitely not fun or healthy.
Lastly, many reptiles do not enjoy each other’s company. The majority of reptiles found in the pet trade are not social. You’ll notice me saying “pet trade” because there is some evidence that some rattlesnakes actually have some social ties, but that’s beside the point. The only communal reptile I can think of are mourning geckos, and that’s about it. If you see ball pythons in a “cuddle pile,” that’s not a sign of affection - that’s a sign of competition and dominance. The snake on top is literally squishing the one on the bottom, hindering it from getting the most out of its available resources…oh, and this can lead to cannibalism because of extreme stress.
Please do not argue that communal set ups are natural, ergo they can and should be done. Fighting, infestation with parasites, starving from lack of food, and death from predation are natural too. However, we are keeping our reptiles as PETS IN CAPTIVITY, which is already unnatural…so it’s a baseless argument. Since the reptiles have no say in whether they can be pets or not, it’s up to us to provide them with the best husbandry possible - even if it means putting their needs ahead of ours.
So to wrap it up - please do not cohabitate your reptiles (unless you have mourning geckos or other odd exceptions).
And for the record - I’m Chinese. Thanks.
NOTE: I adopted a trio of flying geckos (Pytochozoon kuhlii) recently from a friend - one male, two females. I separated them because it was very stressful and heartbreaking to nurse one emaciated female back from the brink, and I wouldn’t wish that upon anyone.
