Why do some hamsters have long faces while others have round faces?

[Pastacat]

I have been wondering about this topic for a while and I want someone informed in genetics to chime in. When I look at Topaç, I see that his face is very rat or mouse-like.
Just look at this photo of him:



He is very mousey here, he even has the boba tea eyes. When I look at other hamster pics, such as this pic I found on Wikipedia:

You can see the difference. The store I bought Topaç from had another animal that I thought was a rat at first, but her, I say her because she had a baby with her, tail was buried under the bedding, so I couldn't be for sure.

What genes play a role in their face roundness? I couldn't find anything online about this subject.

 

[Maz]

It is genetics You usually find that hamsters from official breeders in the Uk are very large and have a more "triangular" face shape - broader heads. Over the decades of pet shop breeding they have developed narrower longer faces sometimes. But individual genetics vary as well.

That second photo of yours doesn't look typical of most hamsters IMO and also there are sadly photos of some hamsters in the US, born with a horrible condition called Bracycephalic syndrome which gives them a shorter nose, and rounder head - it's a horrible condition, they often don't live that long and can have breathing difficulties - and sadly some people actually look for them thinking they look cute.

One of my syrians looked a bit more rat like also - he was so sweet though

 

[Pastacat]

It is genetics You usually find that hamsters from official breeders in the Uk are very large and have a more "triangular" face shape - broader heads. Over the decades of pet shop breeding they have developed narrower longer faces sometimes. But individual genetics vary as well.

That second photo of yours doesn't look typical of most hamsters IMO and also there are sadly photos of some hamsters in the US, born with a horrible condition called Bracycephalic syndrome which gives them a shorter nose, and rounder head - it's a horrible condition, they often don't live that long and can have breathing difficulties - and sadly some people actually look for them thinking they look cute.

One of my syrians looked a bit more rat like also - he was so sweet though

I see. That would make sense. Before I saw Topaç at the store, I was actually planning to buy from a breeder and their hamsters had much rounder faces.

Yes, I have heard about brachycephalic hamsters. I have never seen one in person though. Maybe it's a US thing.

Before I ddecided to get a hamster, I was a bit conglicted about whether to get pet mice or a hamster, but ultimately decided on a hamster because my mother told me not to get mice(she is afraid of them) and mice have slightly shorter lifespans.