Guinea pigs: chewing, bar biting, cables and safe floor time

Quick answer

Guinea pigs do not scratch furniture. They chew it, and they chew the bars of their cage, the skirting board, the carpet and, most dangerously, anything with a wire inside it.

The chewing itself is normal and necessary. What makes it a problem is where it is directed and what it reaches, and the single most important thing to understand is that hay is what keeps a guinea pig's teeth right. Wooden chew toys do not do that job, and a guinea pig that chews constantly but eats little hay is heading for dental disease regardless of how many toys it has.

Floor time is worth doing and it is where almost all household guinea pig injuries happen. Proof the room before the animal is in it.

• Every tooth a guinea pig has grows for life, and hay is what wears the back ones.
• A guinea pig that bites an electric cable can develop fatal fluid on the lungs hours later, even if it seems fine.
• Bar chewing is usually about food, space or boredom, and owners often reinforce it without realising.
• A change in chewing habits, drooling, or dropping food points at the cheek teeth rather than at behaviour.
• Use a playpen rather than free-roaming a room, because the hazards are in the places you cannot see.

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Electric cables are the most serious household hazard for a guinea pig.

A bite through insulation causes burns to the lips, tongue and palate, and the current can trigger a delayed accumulation of fluid in the lungs that develops over the following hours. An animal that appears to recover immediately can be in respiratory distress by that evening. Any guinea pig suspected of biting a live cable needs a vet the same day, whatever it looks like at the time.
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Decide in 60 seconds

Why chewing is not optional

Every tooth in a guinea pig's mouth is open-rooted and grows throughout life. That includes the four incisors at the front, which owners can see, and the twenty premolars and molars at the back, which they cannot.

The front teeth are worn by gnawing. Hard items, cage bars, wood, and the act of biting through fibrous plants all shorten them.

The back teeth are worn by a completely different action. When a guinea pig eats long hay it moves its jaw in a wide side-to-side grinding motion, and it is that lateral movement, repeated for hours a day, that keeps the cheek teeth level. Chewing a pellet or a piece of cucumber uses a shorter, more vertical action that grinds far less.

This is why a diet heavy in pellets and vegetables, with hay treated as bedding rather than as food, produces dental disease even in an animal that appears to be chewing constantly. The teeth that overgrow are the ones nobody can see, and they overgrow into sharp points that lacerate the tongue and the inside of the cheek.

A guinea pig with cheek tooth spurs looks hungry and cannot eat. It approaches food, takes some, drops it, drools, loses weight and eventually stops trying. It is one of the most common serious conditions in the species and it starts with hay.

Behavioural chewing sits on top of that. Guinea pigs explore with their mouths, chew when bored, chew at barriers they want to get through, and chew in anticipation of food. None of that substitutes for hay, and none of it is fixed by buying another wooden toy.

Bar chewing, and the part owners play

Watch when it happens. That single observation usually gives the answer.

Before meals, stopping the moment food appears. This is food anticipation and it is nearly always learned. The guinea pig chews, a human appears, food follows. The behaviour has been reinforced, reliably, several times a day. It is one of the easiest problems to create by accident and one of the harder ones to undo.

The fix is to break the link. Feed at times unrelated to the noise, never approach the cage while the chewing is happening, and wait for a pause before entering the room. Give it a fortnight and expect the behaviour to get worse before it fades, because a behaviour that has always worked is tried harder when it stops working.

Throughout the day, in a small cage. This is a space and stimulation problem. Guinea pigs need floor area, and they need enough of it that they can run in a straight line, because running in short bursts is a large part of their normal movement.

At the point of the cage nearest where you sit. This is a request for company, particularly in a single guinea pig, and the honest answer is a companion of the same species rather than more human attention.

In a previously settled animal. Treat this as a health question first. Hunger from a dental problem, discomfort, and reduced mobility in an arthritic older animal all produce new bar chewing.

There is also a physical component worth checking. Powder-coated bars can flake where they have been chewed, and the coating is then being swallowed. Cages with narrow horizontal bars are easier to get a grip on than mesh panels, and some animals stop simply because there is nothing to bite onto.

Hay in more than one place, at more than one height, with things to push through and hide behind, does more for chewing than any toy sold as a chew.

Floor time, and the room you think is safe

Free-roaming a guinea pig in a room is more dangerous than most owners expect, because the hazards are behind, under and inside the furniture rather than in the open.

Electrical cable is the one that kills. Cables behind sofas, under desks, running along skirting boards, and the trailing lead of a lamp are all at guinea pig height. Use rigid conduit or cable tidies, run cables at height where possible, unplug at the wall what is not in use, and physically block access to the spaces where cables gather.

Skirting boards and door frames. Painted wood is chewed readily. Paint in older houses may contain lead, and even modern paint is not something to eat. Cover the accessible runs or fence the animal away from them.

Carpet and rugs. Guinea pigs pull and swallow fibres. In an animal that cannot vomit, a mass of indigestible fibre is a genuine obstruction risk.

Upholstery and foam. Sofa foam is soft, chewable and completely indigestible.

Houseplants. A number of common houseplants are toxic, including ivy, philodendron, lilies and the bulbs of spring flowering plants. Tomato leaves, rhubarb leaves and avocado are all unsafe. Remove them from the room rather than trying to police access to them.

Gaps. Behind and under appliances, behind kitchen units, under low furniture. A guinea pig that gets behind a fridge is somewhere you cannot reach and next to a warm motor and a cable.

Doors and feet. More guinea pigs are injured by being trodden on or shut in a door than by anything they chew. This is a real argument for a playpen.

Other pets. A dog or cat that is normally reliable is a different animal when a small prey species is running along the floor.

The practical answer for most homes is a playpen on a washable surface rather than a whole room. It contains the animal, contains the mess, removes almost every hazard at once, and can be set up in a minute rather than requiring the room to be proofed each time.

What to give them instead

Hay, first and by a long distance. Unlimited, fresh, good quality, and available in more than one place. If a guinea pig's hay intake is good, most of the dental problem is solved and a large part of the boredom problem with it.

Untreated wood. Apple, pear, willow and hazel are commonly used, from trees that have not been sprayed. Avoid cedar and fresh pine, and avoid stone fruit woods such as cherry and plum.

Cardboard. Plain boxes and tubes without tape, staples, glossy printing or glue. Free, effective, and endlessly renewable.

Hay-stuffed items. Cardboard tubes packed with hay, hay racks that require work, and scattered forage all extend feeding time and increase hay intake at the same time.

Grass and safe forage where you can be certain it has not been sprayed and is not from a roadside.

What to skip: mineral and salt licks, which are unnecessary in an animal on a proper diet and encourage excessive salt intake; brightly dyed wooden toys; anything glued or varnished; plastic; and soft wood shavings sold as chews.

Alert and busy is what you want during floor time. An animal that freezes, hides and will not move is telling you the space is too open or too exposed.

Where the usual advice goes wrong

"Give it a wooden chew toy for its teeth."

Wooden toys help the incisors a little and do essentially nothing for the cheek teeth, which are where dental disease starts. Hay is the dental intervention.

"Spray the cage bars with something bitter."

Bitter sprays are unreliable in guinea pigs, some animals ignore them entirely, and it does not address the reason the animal is chewing. It also puts a substance in a place the animal licks.

"Ignore it and it will stop."

It will, if you genuinely never respond. Most households respond intermittently, which is the reinforcement pattern that makes a behaviour most persistent.

"He chews because he needs more minerals."

Chewing at cage bars and at walls is not a mineral deficiency in a guinea pig on a complete diet with hay and vitamin C. Salt licks are not the answer.

"Let them run around the room, they enjoy it."

They do, and the room is where the cable is. A playpen gives most of the benefit with almost none of the risk.

"The teeth look fine, I checked the front ones."

The front teeth are visible and are rarely the problem. Cheek tooth overgrowth cannot be assessed by looking in the mouth from the front, and often needs proper examination with instruments and sometimes sedation.

The routine that catches problems early

Weigh weekly on a gram scale. Dental disease shows up as weight loss before it shows up as anything you can see in the mouth.

Watch hay consumption, not pellet consumption. A guinea pig eating pellets and vegetables but leaving hay is the earliest behavioural sign of a dental problem.

Look at the chin and chest fur. A damp chin, matted chest fur or a smell around the mouth all point at drooling.

Note when bar chewing happens over a week. The timing tells you the cause.

Check the cage for flaking coating, chewed plastic and damaged fittings monthly.

Reset the floor-time area before every session. Cables, plants, doors and other pets, every time, because it takes thirty seconds and the failure mode is severe.

What never to do

Do not allow access to electrical cable, ever, on the assumption that this particular guinea pig is not interested. They all are eventually.

Do not assume an animal that has bitten a cable and seems fine is fine.

Do not give cedar or fresh pine wood, stone fruit woods, or anything varnished, painted, glued or dyed.

Do not use bitter deterrent sprays on cage bars as a substitute for fixing the cause.

Do not respond to bar chewing by appearing at the cage.

Do not treat a change in eating or chewing as a fussy phase.

Do not free-roam a guinea pig in a room with other pets present, or with a door that anyone might open.

Do not restrict hay to control weight. Hay is the one thing that should always be unlimited.

When to get help

Go the same day for any suspected contact with an electric cable, for drooling or a persistently wet chin, for dropping food, for weight loss, for a guinea pig that approaches food and will not eat it, and for any animal that is quiet and hunched after eating something it should not have.

Go immediately for visible burns in or around the mouth, for fast or laboured breathing, and for a guinea pig that has stopped passing droppings.

Book a routine dental check for any guinea pig whose hay intake has fallen, whose weight is drifting down, or who has changed the way it chews, even if it is still eating.

A guinea pig with enough hay, enough space and enough company chews the things you gave it and rests in between.

Bring the weight record, an estimate of how much hay is being eaten and what type it is, the full diet including pellets, vegetables and any supplement, a video of the animal eating hay and a video of the chewing behaviour, a photograph of the cage, and what the floor-time area contains. If a cable is involved, bring the cable or a photograph of the damage, and say whether the appliance was switched on at the time.