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Cage size is probably the most common mistake made when keeping a community reptile and amphibian terrarium. Space is important in multi-species setups, more so than in setups designed specifically for one species. It’s important that all animals in the cage have room to have their own territory, hunt for food, regulate their body temperature, and otherwise behave normally without the threat of aggressive cage mates causing problems. Standard aquarium sizes are usually too small to accomplish this when multiple species are kept together, and the long, low rectangular shape most are manufactured in is not ideal for community reptile and amphibian tanks. Next time you visit a zoo that has a tank that houses multiple species together make sure to take note of the size of the enclosure. Most are large cubes that that measure several feet in length, width, and height, and a similar cage size should be applied if reptiles and amphibians are kept together at home. For most, a terrarium of this size is not practical or possible to keep in the home and therefore most private hobbyists have difficulty keeping different species together in one cage.

It’s also important to understand that a terrarium offers far less room than wild reptiles and amphibians usually occupy. In the wild there is plenty of room for reptiles and amphibians to go about their business without others interfering. It’s rare for two different species to come near each other unless one is trying to eat the other. When multiple species are placed into a glass cube that is the size of only a small fraction of the space they would occupy in the wild there is a greater chance that something will go wrong or that they will interact with each other in a negative way. Even species that occur naturally together in the same environment generally maintain a large distance from one another, or at least more space than a terrarium can offer.

Predation

One of the most common problems encountered when keeping multiple species in one cage is that one of the species becomes food for the other. Most commonly kept carnivorous reptiles and amphibians will attempt to eat anything that moves. The size of prey that can fit inside an amphibian or reptile’s mouth is often surprising. As a general rule, only keep different species together that are the same size. It’s also important to realize that even though cannibalism may be taboo in most human cultures, it certainly is not off limits to amphibians and reptiles. All animals in the cage, even those that are the same species, should be similar in size.

Conflicting Environments

It’s essential to understand the environmental conditions that different herps need prior to keeping them. Accommodating different environments in one cage is difficult (often impossible in small enclosures) to do. If the environments needed by different species don’t match up they should not be kept together. Particularly important is temperature. Most reptiles should be provided with a range of temperatures in their environment, while most amphibians should be exposed to a smaller thermogradient. It’s often difficult to provide these different temperature requirements in one cage, which makes mixing reptiles with amphibians hard to do successfully. The preferred humidity level is also important to take into consideration. Species from arid regions should never be kept with those from tropical climates, it will not work well. In addition to temperature and humidity, the actual physical environment is important. Some species are aquatic and will need a large water area, while others are strictly terrestrial and can drown in deep water. Some species prefer a deep soil substrate that they can burrow in, while others are arboreal and need different perches and climbing spots. It is hard to provide these different environmental conditions in one terrarium, particularly in smaller cages.

Toxicity

A commonly overlooked problem is the toxicity of the animals being kept. With the exception of two species of lizards, the only venomous reptiles are certain species of snakes, nearly all of which are poor candidates for a multi-species terrarium. On the other hand, there are hundreds of poisonous species of amphibians that are commonly recommended as good species to mix together. Keeping poisonous species of amphibians with other animals is risky for obvious reasons. Some common species of amphibians that are poisonous are fire-bellied toads (Bombina species), red-banded walking frogs (Phrynomantis bifasciatus), fire-legged kassina running frogs (Kassina species), common true toads (Bufo species), Cuban tree frogs (Osteopilus septentrionalis), tomato frogs (Dyscophus species), mantella frogs (Mantella species), and most newts and salamanders. These amphibians should not be housed with others.

Diet Differences

Some amphibians and reptiles that are close to the same size, live in similar environments, are not poisonous in captivity, and wouldpresumably do fine if kept together sometimes do poorly because they require different types of food to eat. Diet is one of the most important parts of permanently maintaining captive reptiles and amphibians. Unfortunately, not all species eat the same food, and those that do often don’t eat the same sizes of food. Both red-eyed tree frogs (Agalychnis callidryas) and blue poison dart frogs (Dendrobates azureus) will eat crickets, but the former of the two will only recognize larger crickets as food, while dart frogs are not capable of eating large feeder insects and need to be fed hatchling crickets. Although feeding both sizes of crickets is one possible solution, this may end poorly because large feeder insects that go unnoticed may attempt to eat reptiles and amphibians that do not eat them first. In the abovementioned scenario, the adult crickets for the red-eyed tree frog could potentially harm the dart frogs. It’s also necessary to understand that not all reptiles and amphibians are equipped equally to catch food. Those that are stronger often bully other weaker species out of food, eventually leading to the death of the weaker species.

What species can be kept together?

So the big question: What species of reptiles and/or amphibians can be kept together? Generally speaking, if you have to ask if two different species can be kept together you should not attempt mixing them because you don’t understand their care requirements enough to do so, and do not have the experience needed to identify common problems that may develop in a multi-species terrarium. Instead, it’s strongly recommended that the different species of interest be kept separately for an extended period of time prior to housing them together. This will give you time to recognize what their normal behavior is, as well as understand what’s involved in caring for them.

One combination that can work well is keeping different North American tree frogs together, such as green tree frogs (Hyla cinerea) and gray tree frogs (Hyla versicolor). Most species require fairly similar care and can be kept together in a large enough terrarium. Avoid keeping Cuban tree frogs (Osteopilus septentrionalis) with other frogs because they are poisonous, grow large, and love to eat other amphibians. Certain species of poison dart frogs (Dendrobatids) have been kept together successfully by some hobbyists. Avoid any species that could potentially produce hybrids, instead sticking to dart frogs from different genera such as Dendrobates azureus with Phyllobates bicolor. Anoles (Anolis species) are a common lizard that is mixed in with frogs, but I would advise against this unless the terrarium is very large and a significant temperature gradient can be provided safely without risking the frog’s safety. It also can be difficult to locate healthy anoles, and unhealthy animals should never be kept with others. Small day geckos (Phelsuma species) have also successfully been kept with certain species of frogs, but again the same precautions should be taken as when keeping anoles with amphibians. As general rule, avoid mixing snakes with other reptiles and amphibians because their care requirements are often different than those of other types of herps. Avoid mixing turtles and tortoises with other types of reptiles and amphibians for the same reason. Aquatic basking turtles, such as painted turtles (Chrysemys picta), red-eared sliders (Trachemys scripta), and map turtles (Graptemys species) may live well together, although it's important to watch for behavior problems and to pay attention to differences in dietary requirements. Larger reptiles are almost always best kept either alone or with others of the same species because they are too difficult to manage when kept in terrariums with other reptiles and amphibian.

None of the above combinations are foolproof or completely safe by any means. Whenever two species are kept together there is a larger risk of problems occurring than when they are kept separate, and it’s important to understand this before mixing species. Those that are listed above are just combinations that I have seen other hobbyists have success with, and are not strict rules to follow. I always urge hobbyists to keep species-specific tanks rather than community terrariums because it is safer for the captive animals.