Typically, mixing species is not a good idea, for several reasons:
1- Even if all of the animals are roughly the same size, larger lizards will take dominance over smaller ones, or even may consider the smaller lizards prey (you would be surprised how large a meal some lizards might go after, especially if they're in a stressful, cramped cage situation). Also, when you first acquire the lizards, they may be the same size, but if you are not familiar with the species, you might end up with one lizard that grows to be twice the size of another. Also, what if one species is more agressive than another? The mellower animals would again end up being picked on, and eventually become ill and die if not eaten.
2- Any "community" terrarium (a term used by fish keepers, any enclosure containing more than one species) must be big. Every species must be allowed its own space, its own basking spot, its own hiding spots and its own feeding areas. You'll need at least double the space that you would provide the species who needs the most. Many types of herps are territorial, so this must be taken into consideration. Particularly, multiple males (of the same, or similar, species) should not be housed together, as they can be very aggressive towards each other.
3- Any animals you mix must come from the same habitat. Aside from the absolutely ludicrous idea of mixing desert species with forest species for example (which, and this should go without saying, NOT be done), even if two animals come from the same place (geographically), it does not necessarily mean that their needs are similar. Microhabitats within larger ecosystems are home to tons of species, and the conditions in microhabitats can be drastically different from the rest of the area the animal comes from.
Imagine this example: You have two lizards that live in the Amazon. However, one is a ground-dwelling skink, one is a tree-dwelling gecko. Although they both live in the same forest, the skink needs slightly cooler temperatures, higher humidity, places to burrow... A totally different habitat than the gecko, who lives in the forest canopy, would need different food than the skink, an arboreal set up, different temperatures and humidity, etc... Two very different needs from two animals that come from the same place.
Mixing species that you would see together in the wild is not a guaranteed success, either. If they get along out there, there could be a slight chance that in captivity they could co-exist in an enclosure. But, in the wild, they are not in an enclosed space where food and the best hiding and basking spots may be limited. Also, it may very difficult, if not impossible for some species, to re-create a portion of that animal's habitat down to the tiniest species of moss. Once an animal is in a habitat unfamiliar to them, you cannot be certain how it would react to other animals.
4- Disease is common among many reptile and amphibian species because so many of them are still wild-caught. Bacteria are almost a guarantee (and other microorganisms could possibly be infecting one or more lizards), and even if they happen to be a kind of bacterium that is not harmful to one of the species you are keeping, if the other animals come from the other side of the world, their immunity to this particular organism is likely non-existant, resulting in one or more sick animals who will need to be separated and get veterinary attention.
5- Reptiles and amphibians, by nature, are solitary animals, only purposely grouping together to either hibernate or breed. Saying that a herptile "enjoys" the company of another, or that two herptiles are "friends," is grossly personifying the animals. Reptiles and amphibians, although some of the more intelligent species can seem to almost display mammal or bird-like personality attributes, do not have the mental capacity to "enjoy" another reptile or amphibian's company, or be "friends" with it.
If all of these possibilities are very real, then why do those animals in the pet stores seem fine when they're housed together?
What many people fail to realize, is that these lizards are stuck in a situation where they are already weakened and stressed from being transported to the pet store (and additionally, if they are wild caught, they are frightened and confused by their new, restricted surroundings), frightened at the noises and constant movement around their aquarium and by the other animals they share it with. Simply put: They are so stressed, confused and frightened that they don't know how to react. Because animals are in and out of pet stores so often, the period they are in these conditions may not do permanent damage to the animal if their next home is a good one. But in most cases, any animals that are housed this way and are not sold by the pet store for an extended period of time do end up sick, and most die.
From article "Mixing Species" at Herptiles.net
Christina Miller
www.herptiles.net
