Size difference: Hamsters are much smaller than guinea pigs, and this size difference can lead to problems. Guinea pigs can easily injure or even kill a hamster, either intentionally or unintentionally. Hamsters may also feel intimidated or stressed by the larger guinea pig.
Diet: Hamsters and guinea pigs have different dietary needs. Hamsters are omnivores, while guinea pigs are herbivores. This means that they need different foods to stay healthy. If they are housed together, they may compete for food, and the hamster may not get the nutrients it needs.
Temperament: Hamsters and guinea pigs have different temperaments. Hamsters are typically more active and playful, while guinea pigs are more docile and laid-back. This difference in temperament can lead to conflict between the two animals.
Housing: Hamsters and guinea pigs need different types of housing. Hamsters need a cage with plenty of space to run and play, as well as a variety of toys and accessories. Guinea pigs need a larger cage with more space to move around, as well as a variety of hiding places.
Illness: Hamsters and guinea pigs can carry different diseases that can be transmitted to each other. This means that if one animal gets sick, the other animal is also at risk of getting sick.
For all of these reasons, it is best to keep hamsters and guinea pigs separate.