Pregnacy in GPs

Question
I recently bought 2 Guinea Pigs from our local pet shop, and we were told they were both girls. I am no expert when it comes to guinea pigs, we have noticed that one in particular seems to be quite plump. A friend has looked and tried to sex them but it seems quite tricky altough she has an NVQ in animal care!!  I am not sure if we maybe feeding them too much, or if there is a chance on of them could be expecting. We bought them at 8wks, and have had them about 4 weeks now.

Answer
Hi Lisa,

It is not actually very difficult to sex a guinea pig once they are over two weeks of age. If there's not obviously a penis or a very non-penis, simply search online for "sexing a guinea pig" and you should ne inundated with instructions and pictoral guides.

Guinea pigs from pet shops are famous for coming with problems. Usually mites, babies, or an unexpected appendage between the legs! Even if they are both girls, it is very likely that they got pregnant in the pet shop. If a female guinea pig comes into contact with a male piggy at any point, she will most likely get pregnant. Guinea pigs are like rabbits in this respect; they mate at the first chance they're given and they don't care if it's with a relative! Males are mature at 4 weeks of age, so if they are older than this (which they should be, if you got them from a breeder or a good pet shop), then pregnancy in a female is possible.

A female guinea pig must be under 6 months old when she has her first litter, otherwise her pelvic bones will have fused together and she will struggle to deliver the litter. There's no such thing as "too young" as in the wild, guinea pigs mate from a very young age, but an inexperienced young Mum will need you to keep a closer eye on her once the babies are born.

The signs of pregnancy are similar as with humans; she'll put on weight, eat more, drink more, and get a bit lazy! The gestation period of guinea pigs is 68-72 days, and when you can feel the babies moving around, she is probably in the later stages of her pregnancy. It is best not to handle her unncessarily during this stage (just when you clean out her cage) as just like a human, she'll be feeling very uncomfortable.

Try not to worry too much. Although, as with any animal, birth can be difficult for guinea pigs, the babies are usually born without any complications, especially if the pregnant sow is happy and healthy. Difficulties in pregnancy and birth are more common in older sows. Defective babies only usually occur if both parents are purebred roans or dalmatians.

When your piggy is looking very big and it's near the end of her pregnancy, put some extra hay in your piggy's cage so that she has somewhere comfortable to lay when she has her babies. She will probably have the babies at night, or any other time you're not watching, so be prepared to open the cage any day now and see mum and 1-4 tiny piggies looking up at you! If you are around when your guinea pig gives birth, don't disturb her, but stay within earshot so you can hear if she is struggling, and have your nearest vet's phone number at the ready.

When the babies are born, they will look just like mini versions of their mum! Not necessarily the same colour, but they are born with hair unlike many other small mammals as in the wild they need to be ready to run from predators from day one! Avoid touching the babies for the first few days (although this will be tempting, as they are very cute) as if you pass your scent onto them, their mother may reject them, and hand-rearing a guinea pig is not easy! You can and should watch them, though. Make sure she isn't too rough when she is cleaning them, and check that all babies get a more or less equal share of her milk. A female guinea pig has only 2 nipples, so if she has 3 or more babies, they will have to take turns to suckle!

The babies can eat solid food from day one so start putting extra veggies in the cage once they've been born, but they will also drink their mother's milk until they are around 3 weeks old. Once they are weaned, you will need to move any males to a separate cage by the time they are 4 weeks old, as at 4 weeks they reach sexual maturity and will be able to get their mother and sisters pregnant! It can be tricky to tell the gender of baby guinea pigs, but by the age of 2 weeks you will be able to tell for sure. If you cannot keep all the babies and need to rehome some, make sure they go in same-sex pairs, and do not give them away or sell them until they are 6 weeks of age.

I've never knowingly had a pregnant guinea pig (my two gave birth unexpectedly), so I don't know much in terms of special things you should feed her. Just make sure you give her a little extra of everything, and keep a careful eye on her. Guinea Pig guru Peter Gurney has some guinea pig health pages at the following address in case you have any problems: http://www.oginet.com/pgurney/index.html

It would be a good idea to take your guinea pig to a vet to confirm that she is in fact pregnant, and to ensure that she is in good health. If you can find a specialist small animal or exotic pet vet, they may also be able to tell you how far along the pregnancy is, so you'll know when to expect the babies.

If you have any other questions about the pregnancy, the babies, or guinea pig health/diet in general, please don't hesitate to get in touch.

Good luck and best wishes,
Jenny.