Hamsters are cute, furry rodents that make popular pets, but they only live for 1 1/2 to 3 years on average. Because of this short lifespan, it's pretty simple to approximate your hamster's age by observing changes in his hair, teeth, size and activity level. The standard-sized Syrian, or golden hamster, has a slightly different development schedule than the smaller varieties -- Campbell's and winter white Russian dwarfs, Roborovski dwarf and Chinese hamsters.
Baby hamsters have several key growth milestones that tell you how old they are.
- The newborn hamster is hairless and pink. He has teeth but his eyes and ears are closed.
- The Syrian baby's ears open at 4 to 5 days old, and his eyes open when he is 15 days old. Dwarf and Chinese hamster's eyes and ears open at 10 to 14 days old. If his eyes are still closed, your hamster is less than 2 weeks old.
- The hamster's fur starts to visibly appear at 7 days old, so if he is still pink and naked he is less than a week old.
- Hamsters begin to eat solid food between 7 and 10 days old, and Syrians are fully weaned between 3 and 4 weeks old, while dwarfs wean by 3 weeks. A nursing hamster is less than a month old.
- Hamsters start to look like smaller versions of their parents when they are 3 weeks old.
The standard-sized Syrian hamster reaches puberty at 6 to 8 weeks old, at which point he will weigh 3 to 3 1/2 ounces. Dwarfs and Chinese hamsters don't mature until 8 to 12 weeks old, when they weigh close to 1 ounce.
- Female Syrians start to breed at 10 weeks old and males at 14 weeks old. While dwarfs mature later than Syrians, they can start breeding as early as 5 weeks old.
- At 50 days old, both male and female Syrian hamsters will begin to fight hamsters of the same gender, so they need to live solo from the age of 10 weeks at the latest. Dwarf species are social animals and can remain in same-sex pairs or groups.
If you notice your hamster has started mating or fighting with cage mates while they used to co-exist peacefully, he is likely going through his troubled teen period, which makes him approximately 2 to 4 months old.
The Syrian hamster ranges from 4 to 7 inches long when full-grown, and weighs 3 to 5 ounces. If he falls within these parameters he is most likely at least 4 to 6 months old -- the age of adulthood for hamsters. Females are often larger than males.
Russian dwarfs grow to 3 to 4 inches long and Chinese hamsters average 4 inches -- even full grown these species only weigh 1 to 2 ounces. The Roborovski dwarf is the smallest species, reaching a size of 1 1/2 to 2 inches.
Hamsters have reached old age at their first birthday, and at this point the hamster's hair might start to visibly thin. He could also start losing weight or have trouble breathing. There are no visible signs to tell whether a hamster is only a year old or 3 years old, but he will start moving more slowly as he ages and eventually his eyes might start to lose their bright shimmer.
You can tell a hamster is at the end of his life if he starts to urinate in his own bedding, since this is not something young, healthy hamsters generally do. If he goes into a corner of his cage or digs under his cage litter, he is likely preparing himself to pass on.