The largest hamster in the world is the black-bellied hamster (scientific name: Cricetus cricetus), and its key characteristics are as follows:
Physical Data
Body length: 20–34 cm (including the tail)
Weight: 400–900 g, close to the size of a small domestic cat
Lifespan: An average of 8 years, far exceeding the 2–3 years of common hamsters
Ecological Features
Distribution: Native to Belgium, central Europe, and Russia
Habits: Nocturnal animals with activity peaks from 7 to 10 pm
Endangerment status: Classified as an endangered species, with France allocating 3 million euros for special protection
Comparisons with Other Large Rodents
Syrian hamsters (golden hamsters) have a body length of only 12–15 cm, less than half that of the black-bellied hamster.
Although the African Gambian pouched rat is larger (up to 91 cm), it belongs to the Muridae family rather than the Cricetidae family (hamsters).
(Note: The black-bellied hamster is a wild protected animal and should not be kept as a pet.)