Basic Guinea Pig Biology

Guinea pigs are fascinating because we have so much yet to learn about them. To help you see how you can monitor their health, we will briefly touch on some parts of the guinea pig's body. Body areas you can check non-invasively for signs of ill health are shown above. Guinea pigs use their eyes, nose, ears, feet and not forgetting whiskers, to sense what is going on around them. This helps them to forage and find food, find their friends, identify threats and explore.

Eyes

Guinea pigs have a wide field of vision but limited sight directly in front of them. They have colour vision, so far shown to be dichromatic. Their eyes get injured by sharp bedding so check for any changes to the eyes such as surface (corneal) cloudiness, redness, ulceration and inflammation. A new study (O'Neill et al. 2024) found that corneal ulceration is one of the most prevalent disorders in guinea pigs; it requires immediate attention as it can be fatal. Early detection means treatment can be very effective. Inflammation can be difficult to see - you can help your piggies by arranging regular check-ups with a knowledgeable, caring vet, ideally a specialist exotic vet. I have found that choosing good quality hay helps prevent this too.

Noses

Cavies do not see well directly in front of them, their sense of smell and touch takes over in this blind spot. Smell is key for communication, finding food and recognising friends. You can really take advantage of their olfactory capacity when creating enrichment for them. Also, when checking their health, don't forget their noses - both their nose and mouth should be free of discharge as this can be a sign of illness, just like people, a runny nose can indicate say a respiratory illness. Candles and sprays produce strong scents or chemicals that may be irritating or even harmful to guinea pigs - they have very sensitive respiratory systems. Consider carefully where is best in your home for their accommodation. Around the nasal area are their whiskers of varying lengths, each length resonating a different sound frequency, enabling judgement of space and textures. They are significantly more sensitive than our fingertips.

Ears

Guinea pig hearing is much better than our own. They have very sensitive hearing, extending into the ultrasonic range, upto 50KHz (McBride, 2017), therefore be aware that certain noises may be aversive (very uncomfortable) to guinea pigs but not us. Be mindful of their reaction to sounds, they may react to sounds you wouldn't expect them too; learning which aversive sounds to avoid around them, in the long-term, will mean your companion animals feel safer and more trusting of you: great for person-piggy friendships! An important point to make here when checking their health, is about head tilt - if you notice a piggy tilting their head, this may indicate an issue with their ears - as always check with a knowledgeable vet.

Teeth

This is an x-ray of Belle, which shows her incisor teeth, at the front of the mouth (labelled). You can see the caudal notch of the superior incisor, where the inferior incisor should sit, behind the superior incisor. The inferior incisor should not sit in front of the superior incisor.

In the wild, guinea pigs would feed on fibrous vegetation, so their teeth are worn down naturally. Piggy teeth grow continuously; unfortunately, due to a lack of owner knowledge, pet cavies may have an inappropriate diet, which can cause or contribute to dental disease. It is vital that pet cavies are given a diet which encourages regular tooth wear to help prevent dental disease. They must have high-quality hay available to them all the time. Research has shown that owners are not always able to distinguish normal front teeth (incisors) from incisor teeth which are too long, causing difficulty eating. Most piggy teeth are toward the back of the mouth where you cannot see them, there could be a dental problem developing without you knowing. This is why regular vet checks are so important. The front teeth (incisors) can become misaligned and grow too long, even into the guinea pig's own flesh. The back molars can develop sharp spurs as they grow, or even form a bridge, trapping the tongue. You can imagine how painful overgrown teeth would be! At present there is insufficient research available, but mineral imbalances and genetic predisposition are also thought to be contribute to tooth malocclusion (when teeth overlap or are not aligned as they should be).

Signs that indicate dental health concerns may include:

poor appetite
decline in number and size of droppings
weight loss
coughing
difficulty swallowing
hypersalivation/drooling (the hair under the mouth will be wet)
lethargy
poor coat condition

You will not be able to see your piggies' back molar teeth but you should try to check the front teeth (incisors) on a regular basis. You should not be able to see the upper incisors growing down past the lip, i.e., outside of the mouth, when closed. The hair on the chin area, under the mouth, should be dry; no drooling evident. Ultimately, piggies need regular vet check-ups to ensure their teeth are healthy.

Feet

Guinea pig feet are vulnerable to the flooring we provide for them, flooring should be comfortable without causing pressure - no wire flooring! In fact, wire or hard surfaces can cause swollen paws leading to the development of pressure sores, resulting in pododermatitis or 'bumblefoot', as it is otherwise known. This can become extremely painful and even spread to the feet and leg bones. Guinea pigs are able to run very fast with amazing manoeuvre skills! It is cruel not to provide them the space they need to express this ability/behaviour. As mentioned before, they have very good spatial awareness, so if provided with sufficient space, once they are familiar with their environment they will soon be doing Formula 1 circuits! This is wonderful to witness, especially for those piggies that have never had spatial freedom.

If you see changes to the way they walk and run, this may indicate an underlying issue such as osteoarthritis (see more here) or it might not necessarily be directly related to their legs/feet. For example, if they start ‘bunny-hopping’, whereby they lift both back feet at the same time, in a move rather like the hop of a rabbit, this could be a joint problem but it could also indicate a bladder problem. Pain may mean piggies may be reluctant to move, so it is worth being mindful of this.

Like their teeth, their nails continually grow; unfortunately in domestic settings they often don't get worn down, they may also start to curl, in this case they will need trimming. Regular trims keep nails a suitable length, preventing pain on movement. A new study (O'Neill et al. 2024) found that overgrown nails are one of the most prevalent disorders in guinea pigs. I find providing plenty of space for guinea pigs to move around, run and explore, as well as a suitable substrate, helps nail wear due to encouraging traction over the substrate. Be mindful that nails can get caught in certain materials, e.g. crocheted blankets, which should be avoided.