Why does a male hamster change personality when he starts living with her

Question

See my hamster Mr.Nibbles has started living with another hamster Katrina and hes more agresive around menot like he used to be :(

Answer 1

Are you looking to breed?  I only ask that because if you are not the female can get pregnant very quickly and you may end up with babies.  

If he is a syrian hamster I would separate them.  They are solitary by nature and are usually only with each other to breed.  

Answer 2

Maybe he's trying to impress his lady friend. . . lol

Answer 3

TAKE HIM OUT NOW!!!!!!! Syrian (teddybear, long haired, blackbear, etc.) are NOT SOCIAL wich means that they ABSOLUTLY POSITIVELY should NOT be with other hamsters in one cage. take the FEMALE out of the cage because she is an intruder. you need to get her a seperate cage. DON'T EVER PUT THEM BACK TOGETHER!! especialy if they r opposite sexes. you sound like u arent ready to breed and YOU SHOULD NOT EVER EVEN THINK ABOUT IT!!! there are too many out there already and you will have to find other homes cause other shelters or pet stores will most likely NOT take them.

Answer 4

they get more aggressive when a female is close to them

Answer 5

His overriding instincts now tell him that his offspring and mate are all-important, so he thinks you might be after them.

In other words, he likes his new squeeze more than he does you.