Guinea Pig Facts Of Life
The most common problem we have found in rescue is the many facts and figures about guinea pig reproduction that are given out by various sources are not actually correct. There are many situations I have encountered recently which have resulted in people acting on what they thought was good advice and ending up with suprise litters.
Hopefully if I can outline the facts and also common misconceptions there might be a few less unexpected litters to deal with.
Pregnancy and Female facts
Guinea pig pregnancies last approxmately 10 weeks, on giving birth to the babies the female is fertile again and if a male is present at the time she gives birth it is more than likely she will get pregnant again. This is called a post partum mating and puts a huge strain on the sow as she is feeding her current litter when she is pregnant with the next one.
Babies should be able to be seen moving approximately 3 weeks before they are born, and just prior to birth the ligament between the pelvic bones stretches and you can feel a gap widening to make room for the babies to be born.
Pregnancy is stressfull as the guinea pigs get very large so it is important not to handle them or try to feel for babies too often preferably not at all, when the babies move you should be able to see it on the Mummy pigs sides.
Whilst pregnant sows need lots of extra vitamin C in the form of fresh fruit and veg, double the amount for a non-pregnant guinea pig. Lots of hay and not too much dried food as an excess of this may cause babies to become very large and difficult for her to push out.
Guinea pigs can give birth to up to 8 babies but the usual litter size is around 3 or four. As a guinea pig only had two nipples large litters may need time for pairs to feed from mum in turn or their diet can be supplimented with warm goats milk fed from a spoon. It is essential you do not syringe feed youngsters as the milk can get into their lungs .
The normal birth weight for a guinea pig is around 80g larger litters will reesult in smaller babies or in a small litter the babies may be larger.
Females come into 'season' and are receptive to becoming pregnant every 16 days.
Females can become pregnant from as young as four weeks of age so it is essential any males are removed before this time including their siblings that are male. Guinea pig females are capable of having babies throughout their lives.
It is dangerous for guinea pigs over one year of age to become pregnant unless they have littered before, the ligament between the pelvic bones become s far less elastic if she has not been bred from by this age. If she does get pregnant the pelvis may not be able to part far enough to allow the babies to pass through. If the babies do get stuck she would have to have a ceasarian section which is a very risky procedure.
Male facts
A baby male guinea pig is capable of breeding when he is around 3 weeks of age or 400g in weight which ever comes sooner. He will start to rumble and may attempt to mount his mother or siblings at this stage it is very important her is seperated and kept with his male siblings or if he is an only boy an older guinea pig male for company.
Older boys may be thought of as sterile if they have not impregnanted a female/s they have been living with for some time. This does not mean he is not capable of breeding, the only sterile guinea pig is a castrated one.
When a boy is castrated he must be kept seperate from females for 5-6 weeks as during this time he may still be able to get a female pregnant as some sperm will still be active in his tubes.
Common misconceptions
My guinea pig is too old to breed.
UNTRUE - only a castrated or spayed guinea pig is definately unable to breed. Females can get pregnant at any age from four weeks and males can get a female pregnant from three weeks old
Brothers and sisters cannot get each other pregnant
UNTRUE - any male or female that is old enough can breed with any other males or females they are housed with inlding their mum, sisters, dad or brothers
You do not need to seperate a litter from each other and Mum until they are 6-8 weeks old
UNTRUE- Baby boys need to be removed at three weeks old or 400g in weight which ever comes sooner, as they will mate their mother and sisters if you wait until they are 8 weeks old it is likely the mum and sisters are pregnant. A very small male may stay in with Mum until they reach 400g in weight someties this does take longer than three weeks but it is essential to watch out for any signs of rumbling or mounting. The earliest I have ever caught a boar trying to mount his Mum was at only 18 days old, he was a single baby and grew very quickly and was sepertaed from Mum at this age.
Baby females can stay with Mum until they are much older, sometimes it is good for mum to have a break and recouperate from pregnancy so at times we remove the girls at 8 weeks and give Mum two weeks to gain condition and have a break then they can be reintroduced. Others stay happily with Mum throughout.
You cannot tell whether guinea pigs are boys or girls when they are born
To an experienced eye it is possible to tell the gender of a guinea pig not long after it is born and the differences should be very clear by the time the babies are three weeks old. If you are in any doubt by the age of three weeks go to your vets or contact your local rescue who should be able to sex your litter for you. It is better to double check to avoid any unwanted pregnancies. Two guinea pigs can become a whole herd very quickly. If a boar and sow are allowed to breed and the boar not removed by the birth things get out of control quickly!
Guinea pig population explosion- an example
Going on an average of four in a litter, and if each litter had two boys and two girls the population could increase like this....
You get a pair of baby 8 week old guinea pigs and do not double check they are the same sex...
Ten weeks later Mum and Dad guinea pig have a litter two boys two girls.... You have 6 guinea pigs
Dad is not removed when Mum gives birth 10 weeks later Mum
has her second litter..... You have 10 guinea pigs
Meanwhile the baby boys or Dad were not removed in time from the first litter,
both baby girls are pregnant 14-16 weeks after they were born they give birth..... You have 18 guinea pigs
In just six months and two weeks from getting that original pair of guinea pigs that you hoped would be great family pets you now have 9 male and 9 female guinea pigs.
The females could live together but for this number you would need a hutch with at least fourteen square foot of space!! So if the were housed in groups it would mean three five foot by two foot hutches for three trios of girls.
The boys can be harder to keep in groups so probably do best in pairs, even if you manage one trio that gets along that is three four foot by two foot hutches and one five foot by two foot hutch to house all the boys.
So that in total is 18 Guinea pigs and 7 Hutches and runs for housing.
Your food, bedding, vegetables, and hay bills are 9 times more than you had expected.
Your vets bills if all your guineas have the same problem and need treatment are 9 times more expensive than you had expected.
If the situation continues....
40 weeks after getting your first two guinea pigs you will have 46 guinea pigs
Just after your original guinea pigs celebrate their first birthday 48 weeks after you brought them home all excited from at your new arrivals you would have 90 guinea pigs!! Your orginal female guinea pig would have had 4 litters. (if each litter born was four guinea pigs two boys and two girls and all girls got pregnant at 6 weeks of age, and all females of age to breed littered every 10 weeks)
I totally understand that the consultation fee charged by a vet can be costly but surely it is cheaper than all that extra expense. Local rescues are ilkely to sex a litter or a newly purchased pair of guinea pigs for free or a very small donation so it is worth giving them a call. Sadly some pet shops do not give the best advice or traning to their staff so it is always best to double check.
If you are having problems with unwanted or unexpected litters you could take your guinea pigs to a vet to be sexed correctly or contact a rescue that may be able to come and visit and at least make sure your guineas are housed in a way to prevent further pregnancies in same sex groups and help with the pregancies that are yet to come to term, then they can visit and sex babies correctly so they can be seperated in time. If you are unsure it is much better to contact a vets or rescue after your first unexpected litter are born. As you can see from the example above things can spiral out of control very easily.
