We all love to make new friends, and it’s great to have companionship. But hanging out with others isn’t necessarily the best thing if you’re an exotic pet. Too many well-intentioned exotic pet owners worry that their birds and exotic animals are lonely, so they allow different species to interact with each other and even to share cages. For most exotic animals, however, interacting with other species is a no-no. Here are a few examples of animals you just don’t want to mix:

Rabbit and Guinea Pig

1. Rabbits and Guinea Pigs

These cuddly, furry pets seem like they would naturally go well together, but they should never be mixed.

Both species may be cute pocket pets, but each carries a type of bacteria in its respiratory tract that may be harmless to the species carrying it but can cause serious, potentially life-threatening infection in the other species.

2. Reptiles, Small Mammals and Birds

Many exotic pet owners tell me how their lizards and turtles like to hang out in the same rooms with their bunnies, rodents, hedgehogs, sugar gliders and birds. One owner actually told me that her tiny gecko liked to sit next to her large rabbit on the couch and watch TV! While those animals may seem to get along just fine, reptiles carry salmonella in their intestinal tracts and shed the bacteria into their stool. While the bacteria may not bother the reptile, it can cause serious gastrointestinal upset and potentially sepsis (infection of the blood) in mammal species in which it is not usually present. Consequently, reptiles should never be allowed around mammals that might pick up the bacteria on their feet and ingest it if they are exposed to areas where a reptile has defecated. Humans, too, can become infected with salmonella after handling a reptile. That’s why it’s essential to wash your hands after any reptile exposure. Finally, birds and small mammals are potential prey for many reptiles, including snakes — so, again, not such a good idea to let them mingle.

3. Hedgehogs and Other Exotics

Unbeknownst to most exotic pet owners, hedgehogs, like reptiles, may also carry salmonella in their intestinal tracts. The bacteria is harmless to them but can spread to other mammals, including people who handle hedgehogs or come in contact with their droppings. Hedgehogs should be kept separate from other pets, and anyone who comes in contact with a hedgehog or its stool should be sure to wash his or her hands thoroughly.

4. Birds With Cats, Dogs and Ferrets

A flying or flapping bird not only captures the attention of a natural predator, such as a dog, cat or ferret, but it also invites those animals to go after and catch the bird. The predatory pet may not even be intending harm to the bird, but even an innocent game of fetch with a bird in the predator’s mouth can lead to devastating injury or even death. Give your dog, cat or ferret an appropriate pet to play with and keep your bird out of reach.

5. All Small Mammals With Cats, Dogs and Ferrets

For the same reasons that birds should not interact with those natural predators, neither should small mammals such as rabbits, guinea pigs, hamsters, mice, rats, gerbils, chinchillas and sugar gliders. These animals are all prey species and may succumb to the hunting behavior of even a playful predatory pet.

6. Hamsters and Hamsters

You’d think that these cute little fuzzy creatures would enjoy romping around with a playmate, but hamsters can be quite territorial and have been known to fight to the death when placed in the same cage. Hamsters do much better as solo pets and do not need cage mates to play with.

7. Reptiles and Other Reptiles

Reptiles such as snakes, lizards, turtles and tortoises have specific temperature, light and environmental needs, and, among different species, those requirements can vary widely. Plus, many reptiles carry bacterial, viral and fungal infections that are contagious to other reptile species. Finally, even similar species of reptiles may fight when housed together. Therefore, in general, aside from a small number of lizards, tortoises and turtles that can sometimes be housed successfully together with other same-species cage mates, different species of reptiles (and even members of the same species) should not be housed together.

8. Amphibians and Reptiles

Just as different types of reptiles have specific dietary and environmental requirements, so do different species of amphibians (frogs, toads and salamanders). While some similar species of amphibians can be housed harmoniously, in general, amphibians should not be kept with reptiles, as these two broad classes of animals have differing nutritional and environmental needs and potentially carry diseases to which the other is susceptible.

Each type of domesticated exotic animal — birds, rabbits, rodents (guinea pigs, hamsters, gerbils, rats, mice, chinchillas, degus), ferrets, reptiles, amphibians and hedgehogs — has its own merits as a pet and its own specific requirements to remain healthy and happy. To stay safe and well, most of those animals should not interact with other species, even if their owners perceive them as lonely. In general, with a few exceptions, such as sugar gliders and some species of rodents (e.g., some guinea pigs and rats) that need to be with same-species counterparts or they may develop behavioral issues, most of the animals do fine with extra attention from their human caretakers and can make well-adjusted companions for people when they are socialized properly.