Guinea pigs and hamsters get lumped together as “small pets,” and because they’re small, it’s easy to assume their care needs are simple, or interchangeable. Neither is true — the two species have quite different housing, companionship and dietary needs, and PDSA guidance is specific on where owners most commonly go wrong.
The single biggest difference: companionship
This is the detail that trips up more new owners than anything else. Guinea pigs are a social species and should generally be kept with at least one companion guinea pig — a lone guinea pig is at real risk of boredom and stress from lack of company, and RSPCA and PDSA guidance is consistent on this point. Syrian (golden) hamsters are the opposite: they are solitary by nature and should be housed alone as adults, since housing them together, even littermates, commonly leads to serious fighting once they reach maturity. Dwarf hamster species vary and some can sometimes be kept in same-sex pairs from a young age, but this needs care and close monitoring, and separating at the first sign of conflict.
Getting this backwards — a solitary hamster kept alone when it needed company, or worse, hamsters housed together that then fight, or a single guinea pig left without a companion — is one of the most common and most preventable welfare problems in small pet care.
Housing: bigger than most starter cages
PDSA guidance points to specific minimum benchmarks that are larger than a lot of commercially sold “starter” cages:
- Hamsters: PDSA cites roughly 100cm x 50cm of usable floor space as a reasonable minimum, with room for at least 25cm depth of bedding to allow natural burrowing behaviour. Wheel size matters too — PDSA suggests at least 30cm diameter for Syrian hamsters and 20cm for dwarf hamsters, with a larger wheel if the individual animal needs it, since a too-small wheel forces an unnatural, arched running posture.
- Guinea pigs: need considerably more floor space than a typical pet shop hutch provides, plus safe, separate space for exercise, and (for outdoor hutches) proper protection from weather extremes and predators.
Diet: species-specific, not interchangeable
Guinea pigs, unlike hamsters, cannot produce their own vitamin C and need a diet that reliably provides it — primarily good-quality hay (which should make up the majority of their diet) plus fresh vegetables and a small amount of guinea-pig-specific pellet food, since a hamster diet or generic “small pet” mix won’t meet this need.
For hamsters, PDSA identifies suitable fresh foods including carrot, broccoli, cabbage, cauliflower, spinach, sweet peppers, cucumber and courgette, plus small amounts of herbs like basil, parsley and coriander, and fruits such as apple, pear and melon in moderation. Certain foods should never be given to hamsters: citrus fruits, rhubarb and grapes are specifically flagged as unsuitable. Both species need constant access to fresh water and a species-appropriate dry food base, with fresh food as a supplement rather than the main diet.
Introducing companions safely
Simply putting two guinea pigs together isn’t advisable without some care. PDSA-aligned guidance recommends introducing new guinea pig companions on neutral territory first — somewhere neither animal already considers home ground — before moving them into a shared permanent enclosure, to reduce territorial conflict. Watch any new pairing closely in the first days and be prepared to separate temporarily if there’s persistent aggression rather than normal settling-in squabbling.
A quick comparison
- Guinea pigs: social, need a companion, need dietary vitamin C, active during the day, generally calmer and easier to handle for children under supervision.
- Syrian hamsters: solitary, must be housed alone as adults, mainly active at night (crepuscular/nocturnal), need a large wheel and deep bedding for burrowing.
- Dwarf hamsters: sometimes sociable in same-sex pairs but need close monitoring, generally faster-moving and can be harder to handle safely, especially for young children.
Both species make genuinely good pets when their specific needs are met — the key point is that “small” doesn’t mean “simple,” and the housing, diet and companionship requirements deserve the same research as any other pet before bringing one home.