Winter whites mating !!

Question
QUESTION: Hi, Two and a half weeks ago we bought two female winter whites aged 4 weeks.They have until now been fine.However,over the last couple of days,one has been mounting the other at every opportunity.I suspect this is not normal for "sisters", or is it ? I have tried to sex them after seeing this behaviour.On one you can clearly see the opening's about 1cm apart.On the other you can barely see any openings at all (this one is also slightly smaller and the one being mounted).Alarms bells are ringing !! Can you advise us please ?

ANSWER: Hi Rod

It could be that they are the same sex and they are squabbling - do you know if they have always been together/are they related?  One will always want to be the dominant one and it could just be that they are trying to show who is boss.  If this is the case, then it is important that they don't continue behaving like this - sometimes the dominant one bullies the other one and they can make their life a misery.  They should be able to sit together, play together and sleep together.  If one is always being chased, sleeping alone or there is a lot of squabbling then they would need to be separated permanently.  Hopefully it won't come to this.  

Regarding their sex - then this is definitely something that needs checking.  The smaller one could perhaps just be younger and not as well developed for you to be able to clearly sex her/him.  It could be that they are related but are from different litters.  The only way really is to keep looking and comparing them - here are a few sites that might help you with this: http://www.youtube.com/watch?v=63SohHao5hA
http://www.hamsterific.com/HamsterUniversity/SexingHamsters.html
http://www.animalloversweb.com/cgi-bin/forum/Blah.pl?m-1199290713/

However, from the description you give it sounds as though one could well be male.  If you discover one is a male, then the important thing is to separate them straightaway in case the female is already pregnant otherwise they will mate again the day she gives birth. The usual gestation period for a dwarf is 18-21 days.   If you think they are opposite sexes I think you should go back to the pet shop and tell them - after all they should have sexed them although some pet shops have disclaimers up in case they make mistakes.  They may at the very least let you have a cage so you can separate out the male.  If you discover one is pregnant then you could see if there are any girls in the litter and if so they could live with mum.  If you are happy with the idea of having more than one cage and are certain that they are opposite sexes, then you could perhaps put a divider into the cage so that the male can smell the mum and if she has babies he will be able to smell him but not actually get to them.  This really depends on how big a cage they are in and what type of cage it is.  When the babies are 3 weeks old every day swap some of the bedding from one side to the other so that their scent is everywhere.  Then at 4 weeks you could sex and separate out the the boys.  You could try putting them in with dad and the girls can live with mum.  The danger is that they may fight and if this is the case you would end up with even more cages!  

If you think they are different sexes and you separate them unfortunately it would be very difficult to get other adult hamsters and introduce them.  I have heard of it working but as a foster home I often end up with single male dwarf hamsters because no one has been able to introduce them to another one.  Again, it would be worth discussing the situation with the pet shop as they may agree to taking them both back and letting you start again.  Alternatively, do you have a local hamster rescue?  If so it might be worth getting them to sex them both - they are experienced in this and they can at least put your mind at rest or they may offer to help you if you find yourself with more than originally planned.

I hope you get on OK.

Regards

---------- FOLLOW-UP ----------

QUESTION: Hi Sheila, Thanks for your reply.Just to follow up on a few of your points.They were from the same litter and when we bought them they were supposed to have been seperated into boys and girls.Since I sent my first question their behaviour has been normal,they sleep together etc and generally get on well.It seems that there was just that day or so of frantic chasing and mounting,however we still think there is a difference when you check their genitalia.

Answer
If you are concerned that they may be opposite sexes then it would be a good idea to get someone to check them for you so that you know whether or not you will discover a litter. If they are definitely confirmed as being opposite sexes then you have a choice as to whether to separate them immediately or divide the cage so that the male could live temporarily on the other until any males in the litter are 4 weeks old and can be separated from mum.  Don't forget that if the female does produce a litter they will mate again the same day and a second litter will arrive 18-21 days later!

I'll be interested to find out what you decide.

Regards