@Brian W. That's a valid concern. I think it has to be addressed on a case-by-case basis. Most recently (since the beginning of 1993), I've adopted and been personally responsible for the care of cats, rabbits, gerbils, one Syrian hamster, 5 goldfishes, and 4 Rosy Red minnows.
I've found that cats are unpredictable. My first cat was apparently happy as an only cat. The next two I adopted (Riley and Phil, a month apart) hung out together and liked each other (although they often had smackdowns which usually started when they tried to groom each other and each wanted to groom rather than be groomed). I eventually adopted another cat, who got along better with Phil than with Riley, but everybody basically did fine.
Syrian hamsters can be notoriously anti-social with others of their own species, and I didn't try to find him a companion of his own kind. I adopted my 5 female gerbils in 2 groups about a month apart; they had originally been in the same cage, but the two times I tried to reintroduce them to each other, they started fighting so I immediately separated them and kept them in separate cages.
My first rabbit had been in a cage by herself, and appeared to be happy as an only rabbit. After she passed, I adopted two unrelated males (Hans, a mini-Rex, and Franz, a Dutch dwarf) from the same cage in the shelter. They were getting on each others' nerves when Franz started to become sexually mature (he had been too young for neutering when I first adopted them), but after first Hans and then Franz were neutered they spent most of their time together (although they each had their own cage).
My goldfishes liked to shoal together. I'm not sure about the minnows, but they definitely didn't fight with each other.
So you can make general assumptions about different species, but usually you have yto take it on a case-by-case basis.
I've found that cats are unpredictable. My first cat was apparently happy as an only cat. The next two I adopted (Riley and Phil, a month apart) hung out together and liked each other (although they often had smackdowns which usually started when they tried to groom each other and each wanted to groom rather than be groomed). I eventually adopted another cat, who got along better with Phil than with Riley, but everybody basically did fine.
Syrian hamsters can be notoriously anti-social with others of their own species, and I didn't try to find him a companion of his own kind. I adopted my 5 female gerbils in 2 groups about a month apart; they had originally been in the same cage, but the two times I tried to reintroduce them to each other, they started fighting so I immediately separated them and kept them in separate cages.
My first rabbit had been in a cage by herself, and appeared to be happy as an only rabbit. After she passed, I adopted two unrelated males (Hans, a mini-Rex, and Franz, a Dutch dwarf) from the same cage in the shelter. They were getting on each others' nerves when Franz started to become sexually mature (he had been too young for neutering when I first adopted them), but after first Hans and then Franz were neutered they spent most of their time together (although they each had their own cage).
My goldfishes liked to shoal together. I'm not sure about the minnows, but they definitely didn't fight with each other.
So you can make general assumptions about different species, but usually you have yto take it on a case-by-case basis.
