Hey! I don't actually own a guinea pig, but basically, a friend of mine is pig-sitting a guinea pig of another friend who's away traveling. My pig-sitting friend noticed that the guinea pig started constantly making these grinding sounds. She just cleaned his cage and he's constantly making these very loud sounds. Even when giving him something to chew and eat, he would immediately start again afterward. Both of us have no experience with guinea pigs and we're trying to do some research. I found this forum so I'm trying my luck here. Does anyone have any ideas?
What it sounds like:
Hi and welcome
Constant teeth grinding can be a sign of overgrowing back teeth or pain.
Signs of Pain in Guinea Pigs
Have a look at the incisors: do they have an even edge, or is the edge slanted (one sided chewing) or jagged (uneven chewing) or are the edges no longer meeting and the incisors are pointing inwards (overgrown premolars and molar teeth). If one of the incisors has a funny colour, then there could be a problem with it (potential root abscess). This is not fail-safe but it is the best way of making a quick assessment of whether there could be a potential problem with the teeth or not.
In a balanced dental system, the 4 incisors at the front are self-sharpening against each other; they are there to pick up and cut the food while the chewing back teeth do the grinding down of the tough hay/fresh grass fibre. Their constant fast growth rate has evolved against the very abrasive silica in grass/hay fibre, which should make at least three quarters of the daily food intake for long term dental and gut health and a longer healthy life span.
Vegetables and pellets only replace the supplementary role that wild forage used to have. Too much of it and a constant supply of pellets can mean that a guinea pig is eating less hay than they should.
Please step in with weighing daily at the same time on your kitchen scales (instead of once weekly) so you know whether your piggy is eating enough or whether they are losing weight. You cannot control the hay intake by eye.
Here is the practical detailed information, which we cannot repeat in every post.
Please take the time to read the very helpful how-to links:
Weight - Monitoring and Management
How To Pick Up And Weigh Your Guinea Pigs Safely (videos)
Long Term Balanced General And Special Needs Guinea Pig Diets
If your piggy is having a problem and is losing weight, then you may find the detailed practical how-to care and feeding advice in these links here very helpful:
Emergency, Crisis and Bridging Care until a Vet Appointment
All About Syringe Feeding and Medicating Guinea Pigs with Videos and Pictures
I am very sorry for your worries. It is always so much more stressful when it is not your own but somebody else's guinea pigs you are looking after.