Gender ratio in hamster litters?

[lmh]

Does anyone know anything about 'gender ratios' in hamster litters?? My litters tend to have far fewer females compared to males. Is this pretty normal for everyone else also??
I have been reading and come across some very interesting information about this and I would like to compare that information I found to some of the breeders here. What are your average gender ratios? Do you have all of your female hamsters together in the same room? Are you males in the same room also? How many breeding females compared to males do you have housed in the same room *OR* what is the ratio of breeding females vs males being housed in the same room?

You can private message me the info if you dont want to make some things public.

Litter size 13- 6 boys/3 females (4 unknown/2 died on day two, 2 on day 10)
Litter size 18-11 boys/3 females (4 unknown/culled day 2)
Litter size 16-12 boys/4 females
Litter size 16-12 boys/4 females
Litter size 15-10 boys/5 females
Litter size 13- 9 boys/4 females
Grand total 91 64 BOYS/27 GIRLS (8 UNKNOWN)

Curiosity has the best of me on this topic....

[POLAR WHITES]

I think the heat has some thing to do with gender of pups might be worth looking into

[Vectis Hamstery]

All my hamsters live in the same room (except any ill or in quarantine). I have found over all my litters that generally the ratios are even - though some litters may be more male or female heavy. I don't label my hamsters as 'breeding' males or females so can't answer that part of your question.

[Pompompoms]

I also don't have set breeding males of females, they all live as pets and then I will pair up for breeding when the time is right. I have boys in one room and girls in another, pairs I am hoping will produce litters also tend to live together in the boys room. I mostly breed one litter at a time, but when I have beed breeding two pairs they have been in the same room, but at opposite ends.

I breed robos so litter sizes are smaller.

1st litter - 6 pups, 4 boys, 2 girls
2nd litter - 4 pups, 2 boys, two girls
3rd litter - 4 pups, 2 boys 1 girl, 1 sex unknown passed at three days old
4th litter - 8 pups, 4 boys, 3 girls, 1 sex unknown passed one day old
5th litter - 4 pups, 2 boys, 2 girls
6th litter - 8 pups, 6 boys two girls.

[lmh]

Polar - I havent come across anything about heat/temp and ratios...but that is something that I will look into also. Thanks!

Vectis - Perhaps the use of the term of 'breeding' hamsters was incorrect - sorry about that. Yes, they are all pets. I guess basically what I was asking is if the girls that do get pregnant are in the same room with other girls and/or boys.

Pom - I think the information was only about Syrian's but I am thinking it would carry over for other kinds too?

Originally I was looking for information on my litter sizes - but then ran into information about gender ratio and it caught my eye because the ratios in my large litters are so great. (at least I think they are, that is what I am now trying to figure out). lol Anyway - the research was done with one group of hamsters being away from and housed seperately from other females and males. Another group did a harem type of living situation with multiple females to one male. The hamsters from the harems produced more males then females.

I have all my females in the same room with two males (with other males are thoughout the house). I was wondering if just keeping all the girls close to eachother would have the same affect as the hamsters that actually lived together in the harem type situation - - and that is why my boy ratio is so high?? In a nutshell, 'because they smell all the other girls and produce more boys'. anyone else ever heard of such a thing?

I personally dont mind the ratio difference, I am not going to try to change it - I was just curious about the subject matter.

[zuhzoo]

I have some ideas about this topic too. The only animals I know of that have sex ratios affected by temperature are those that lay eggs, so can't comment on that.

The first thing I want to say is that humans have a biased sex ratio at birth towards males, but not as high as that you have seen in your hams! This evens out as unfortunately males are more likely to die In my degree they taught us that it might be because the 'Y' sperm are lighter than 'X' sperm, and so are more likely to reach and fertilise the egg as they are hindered less.

OK so I was thinking about why there are so many more males in your litters, and I found two papers for you to have a look at:
http://www.sociallearning.info/stora...%20539-546.pdf
http://www.sociallearning.info/stora...42%2081-90.pdf
These are basically just saying that there wasn't such a big sex bias in C-section litters than naturally born ones. What they have gathered from this is that female rodents (one also looks at syrians) either purposely kill females, or just don't care about them as much as the males, so they are more likely to die. The effect was larger in larger litters, so this is where I'm guessing the culling of pups come in- the mother may choose to make the litter smaller but only culls females, or mostly culls females. It would also mean that syrians would have more biased litters as they have larger litters!

The main other thing I can think of is that there is a hypothesis that if there is a sex bias it will be because there is a benefit to this- maybe living with so many females is changing the sexes that dominate in litters? Especially as a lot of breeders would have more females than males, I am guessing many people would also have the male bias effect. So the harem study you mentioned makes sense!

Finally, the last thing I can think of is that maybe males that produce more 'Y' sperm are more successful (have more grandchildren etc through their male offspring) so there is a genetic tendency towards producing more males?

Anyway, I hope at least some of that information was useful or new to you, I am not sure how much you have looked up!

[lmh]

Zuhzoo - Very interesting!
I wish I would have sexed the babies earlier to see if the 'nursing males vs females' research happens the same with my litters also. They are now all at the age that they are starting to sleep away from mom in their own nests and are drinking more from the waterbottle then nursing. BUT there are some that are still really 'clingy' to mom...lol Mommas Boys!

I do know that I have seen MANY times that babies of one color are nursed together on one side and babies of another color are nursed on the other side. lol Goldens on one side...BEC's on the other side. Seriously. Its not all the time, but it has happened enough to catch my attention! I wonder what that is all about??? Anyone else noticed that?

I still have to read the paper on the second link that you sent - I appreciate so much you sending them to me.
The information is fascinating!

Lora

[zuhzoo]

Glad you liked the info! It would be interesting to see whether males are nursed more often!

It is really interesting about the colours being separated... I am not sure exactly why that would happen. I read about female birds preferring birds that look like their parents, and stallions that prefer certain colours of mares to breed, so I definitely think that at least some animals can have biases towards certain colours, maybe especially similar ones to their own. It could be that the mom hamster is giving preferential treatment to babies of certain colours, or that when the babies can see they prefer their siblings that look like them? But if the mom hamsters just arrange the pups that way I have no idea :P They are super organised!

That's okay, I find all of this stuff really interesting too

Zoe