Cavies come with certain tasks. They are generally not very tiring or time-consuming, but when you are a newbie, some could be challenging.

Measuring weight

Cavies are prey animals, so in order to survive they must hide all their symptoms as long as they can. Predators always choose the easy dinner.
When you can see the problem, it is often too late, so it is crucial to measure their weight. Weight loss is the most obvious sign of sickness, so it is important to check it in a weekly basis. Keep these records, so that you can easily notice any changes.

Kitchen scales are perfect for guinea pigs, you can buy one for about 20 euro.

If you notice a weight loss, examine the animal. If the loss is not significant and the cavy doesn't look suspicious, measure it again after a few hours later and in the following days. If the weight isn't dropping anymore or the cavy regained the previous state, do not worry.

The result can vary, it depends on how full their gastrointernal tract and bladder are. To get a more reliable data, try to measure them in the morning before feeding. The difference could easily be 40-60 g in the case of an average-size adult.

If the loss is more than 5% and/or the animal seems unusual, bring it to your vet. If the animal doesn't eat, you have to feed Critical care with a syringe until professional care is available.

When you experience small but continous loss that takes for weeks, it is also a cause for alarm. 

Trimming nails

Pet cavies don't run too much and their bedding is generally soft. Unfortunately it means that they aren't very good at wearing out their nails. Overgrown nails could cause serious problems, in advanced cases cavies cannot even stand on their legs.
Fortunately this stage is hard to reach, and monthly trimming can prevent troubles to occur.

They have four nails in each forelegs and three in the hind legs. There is a quick in each nails, our goal is not cutting the quick.

If the nail is light or translucent, it is easy not to miss the right spot. Darker nails are more challenging. With the help of a light you can check the quick. If it's not possible, cut smaller pieces.
In case of an accident you should use soap. Pressing the nail into a bar for a few seconds ends the bleeding.
If your cavy has seriously overgrown, curved nails, cut them weekly, each week a tiny part only. In time the quick will gradually move back, but if the case is a serious one it could take months to reach the normal state.

In general cavies aren't into nail trimming. The more docile ones do not resist. If you are not that lucky, it might requires two people to cooperate: one can hold the cavy while the other trimms.
Some piglets try to bite in order to avoid this unpopular treatment. It could be handled by using a towel to cover the head of the animal. 

Certain cavies can be bribed with some delicacies. If your guinea pig fight hard against the procedure, it may worth a try to distract him or her.
In worst case you can turn to your vet.

Checking the guinea pig

When you measure your piggie, it can be combined with some basic examinations. These can detect certain conditions early and it also help your piglet to get used to these procedures. When you have to bring him or her to the vet, it means much less stress for the animal if you two regularly practise this routine.
Things to check:

* gently inspect their fur looking for wounds. It could be a sign of parasites or fight.

* the presence of bald areas could mean parasites, but if it's in both sides of the abdomen of an adult sow, it could also be the sign of ovaryan cysts. Right behind the ears they don't have hair.
* carefully open their mouth and look their incisors. In case one of them is broken, check it daily. If it does not grow back in a normal way, your vet has to correct it.

* touch every part of the animal to look if there's any sign of pain.
* look the sole of their feet for wounds or ulcer.

* by holding the cavy take a look of their anal sac. When it's normal there's not much to see, but if it starts to fill in, that is conspicuous. This problem almost never occurs in the case of sows or young boars. Adult male animals are the most affected.

* touch the sebaceous gland on their butt. It is slightly above their anus. It should not be sticky.

* look into their ear canals. Healthy ears are slightly greasy, but the presence of liquor is not normal. If your eyesight is sharp enough, you can also notice the presence of ear mites.

* finally, their eyes should be examined too. Sticky, secretory eyes are not the sign of health. 

The perianal sack lies between the anus and the genital. It procudes important enzymes. Cavies normally keep it clean by themselves, so just leave it to them unless you have a reason to doubt in their skills. Older, obese boars are  the most affected by this problem. When the sack is full, use cotton buds soaked in baby oil, and be very gentle.

The sebaceous gland on their back is visible even from a distance if it's a short-haired cavy. The greasy secretum is normal in lower quantity. If the fur is sticky, you should use lukewarm marigold tea to clean it. If the gland is plugged, it could cause painful infections. In this case you should bring your cavy to a vet.

Guinea pigs produce a cleaning secretum through their eyes. This is a white, dense liquid. If the eyes aren't red or swollen, and the animal can keep them open easily, do not worry, most likely you happened to see this process.

Bath and grooming

Guinea pigs have extremely sensitive skin. The epidermis, the upper skin layer is very thin, escpecially in coated areas. There are sebacious glands that extract lipids. These lipids works as a natural protection, they don't let moisture out, so the cavy can regulate the hydration of its skin.
When you bathe the animal, especially when soaps or shampoos are involved, you hurt this lipid layer, and this harm can cause the skin dessicated.
In this state the skin cannot function properly, it is no longer the important barrier that protects the animal from the outside world. Besides, their skin is naturally acidic (ph 5.3-5.8, depends on the area), while the water is ph 7.0, and the chemicals are alcaline, over ph 7.0. The changing pH turns the surface of the skin more suitable for harmful microbes.

So please do not bathe your guinea pig unless it's really necessary.
The justifiable cases:

* vet orders a bath, mostly for treating funghi infection. Follow the orders.
* the fur is heavily soiled, most likely around the bottom of a long haired cavy, or when using inefficient bedding. Diarrhea can be a cause too.

Use lukewarm water without chemicals. The water level should be shallow. Give some time till the sticky parts loosen a bit. If it doesn't help, cut that hair. It's worth to keep their hair short around their butt if it's a regular problem.
Make sure no water is reaching their head, especially not getting into the ear canal. Use a hair-dryer with moderate temperature. Constantly check the temperature of the hot air.

Short-haired cavies do not require much grooming, however the longer coat can stick together if you do not comb regularly. Be gentle during the process.