Guinea pigs make wonderful pets and in general by nature they are extremely friendly characters. Most of these cute little creatures do not bite because they are known to be gentle so when they do bite, they usually have a good reason for doing so. It would be fair to say that a very young cavy might give you a nip, but this is only because they are still learning and exploring everything that's around them. Like all young creatures they are testing the limits of how far they can go.
It's important for owners to appreciate that guinea pigs communicate in all sorts of ways and if they do nip anyone, it's usually because they are trying to let them know they are not happy about something. It could also be because they are in pain. Most people soon gets to know their pet's personality which helps them figure out if something is amiss or not. But if you are new to keeping these delightful little characters, it can take a while to understand them and the things they do.
As previously mentioned, a guinea pig will generally only bite when they are not happy about something and this includes when they are picked up and carried. Cavies are not overly fond of being carried nor are they happy when held because it makes them nervous. If held in a certain way, your pet may just give you a nip to remind you they don't like what you are doing. However, if there's a lot of noise going on or if your pet is a situation they are not familiar with, this may well frighten them and the result is a nastier bite.
The other thing to bear in mind is that if you pick your pet up and hold them and they need to urinate they will typically start fidgeting and trying to wriggle out of your grasp. You might end up with a nip which you should not ignore because if you do, your cavy might bite a little harder the second time round. Guinea pigs need to empty their bladders on average every 15 to 20 minutes so it's worth remembering this when you want to pick them up and hold them for any length of time.
If your cavy is normally kind and gentle but suddenly starts biting you, then you should check they have not picked up any parasites or mites. Your pet may also be feeling unwell which means a quick trip to the vet might be in order. If they have got mites, this can make their skin very sensitive to the touch so when you pick them up, it hurts them and they retaliate by nipping you.
The problem is that mites found on guinea pigs are not visible to the naked eye but they can be transmitted from one cavy to another. You would need to get a specifically formulated treatment for use on guinea pigs which your vet would be able to recommend or even prescribe. You would need to repeat the treatment 2 to 3 times in order to get rid of the mites which are very resilient parasites. It is really very important to treat guinea pigs when they have mites because if the condition is left untreated, it can prove fatal to cavies who may suffer a seizure.
You should always take a guinea pig for regular health checks at the vet because another reason why they might suddenly start biting is because they have tooth ache. It's their back molars that are usually the culprits causing a condition called malocclusion. You may find they are chewing on things in their cages more than usual and when you pick them up, they bite you. Malocclusion is a very serious condition that can prove fatal if left untreated due to the fact your pet will stop eating due to the pain and discomfort this causes them.
Other reasons why a guinea might bite you include the following:
The majority of guinea pigs are friendly little creatures that boast kind natures. However, when they are unhappy about a situation or if they are in pain, they might just give you a nip to let you know. With this said, some cavies just have attitude"" which could be because they were mishandled when they were young which can be the case if you rescue a guinea pig from an animal shelter. If this is the case, you just have to show a lot of patience and be careful when first handling your new pet. Once they start to trust you, they may stop nipping but this may take a little time. The one thing you must never to do is punish or tell your guinea pig off because this will end up frightening them which could make matters worse.