[Drago]

Sometimes the hair thins on hamsters at various times for various reasons. How much protein is he getting in his diet? Too much or too little can lead to hair loss. It's possible that it could be due to poor breeding as well. I'd keep an eye on it and if it seems to worsen or he seems to do poorly, then I'd consider consulting your vet

Edit: I just wanted to add that Duncan has the same spot near his ears come to think of it. Although Duncan has always had coat issues..