I have several hamsters,but one of them is very lethargic and seems to be asleep all the time(I mean more than normal).The other day his cage was cleaned out and he stayed asleep the whole time!We think he could be in hibernation or something similar,he isn't old(15 months)and we have one of his siblings who is in good health and two other hamsters in the same room who aren't like this.Any advice please?

if he's hibernating i.e. not coming out at all you really really need to bring him around

hamsters use hibernation as a last ditch attempt to survive
they don't do well with it though and can easily die
is he cold at all when you touch him?
is his breathing slowed?
how is his surroundings? cold or draughty?


if he is emerging for food/water then a trip to the vet might be in order as it could be an infection

15 months in some hamsters is when they begin to slow down anyway as they age
i would expect it more at around 18 months, as this is when mine began to slow, untill ultimately passing after a stroke at 23 months

He is eating when I wake him up and feed him,other than that he won't come out to eat or drink!When he does wake up he is in good health running around in the hall and such.He has a female sibling who is in great health and is a bundle of energy.I don't think the room is too cold but I'm not a hamster!One of the hamsters he shares a room with is his dad who is in great shape and we see every day.

ours went like that before he died

how old is your hamster? - sorry, i reread - 15months

ah, i see

unfortunately, every hammy is individual, it sounds likely that it could be that he's slowing down due to his age