Rabbit caecotrophs: sticky bottom and the diet behind it

Quick answer

A healthy rabbit produces two completely different kinds of droppings, and you should only ever see one of them. The hard, round, dry pellets are waste. The soft, dark, shiny clusters called caecotrophs are food, and a well rabbit eats them straight from the anus, usually overnight, so the owner never notices.

If you are finding squashed, sticky, strong-smelling clusters in the hutch or matted onto your rabbit's bottom, that is not diarrhoea. It is caecotrophs the rabbit either did not want or could not reach, and the two causes have completely different solutions.

In most cases the answer is in the bowl. A diet too rich in starch and protein produces more caecotrophs than the rabbit wants to eat.

• Uneaten caecotrophs are not diarrhoea. True diarrhoea means no normal hard pellets at all, and that is an emergency.
• The two causes are a diet that is too rich, and a rabbit that physically cannot reach round.
• A soiled bottom in warm weather is a flystrike emergency waiting to happen. Check twice daily.
• Fixing it usually means more hay and fewer pellets, reduced gradually over weeks.
• Never bath a rabbit to clean it. Rabbits panic in water and can break their own backs struggling.

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A dirty rear in warm weather is a flystrike risk, and flystrike kills rabbits.

Flies are attracted to soiled, damp fur and lay eggs within hours. The maggots hatch and begin eating into living tissue, and a rabbit can go from a slightly dirty bottom to a life-threatening emergency in less than a day. Any rabbit with caecotrophs stuck to its fur must have its rear checked, gently cleaned and thoroughly dried at least twice a day through the warm months, and any rabbit found with maggots, or with a wound or a foul smell around the rear, needs a vet immediately.
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What caecotrophy actually is

A rabbit eats plant material that mammals cannot digest, and it solves that with fermentation in a caecum that is very large relative to its body.

Food travels to the small intestine and then to the colon, where something remarkable happens. The colon sorts the contents by particle size. Large, indigestible fibre particles are pushed onward and leave the body as the familiar dry, round, fibrous pellets. Small particles and fluid, which contain the fermentable material, are moved backwards into the caecum.

In the caecum, a dense microbial population ferments that material and generates volatile fatty acids, microbial protein and B vitamins. That output is then packaged in a mucus coat and passed as caecotrophs: soft, dark, shiny clusters like a bunch of small grapes, with a distinctive strong smell.

The rabbit takes them directly from the anus and swallows them whole, so the mucus coat protects the contents until they reach the stomach. This normally happens in a quiet period, often overnight or in the early morning, and it is why owners of healthy rabbits go years without ever seeing one.

Two consequences follow. First, a rabbit that stops eating caecotrophs is losing a meaningful part of its nutrition. Second, a rabbit that never eats them at all is producing a wet, sticky, fly-attracting mess in a place that is hard to clean.

Cause one: the diet is too rich

The caecal microbial population is shaped by what arrives. A diet dominated by long fibre produces a stable population and firm, well-formed caecotrophs in a quantity the rabbit wants to eat.

A diet high in starch, sugar and protein does the opposite. Fermentable carbohydrate reaching the caecum shifts the population, production increases, and the caecotrophs become softer, pastier and more plentiful than the rabbit will consume. The surplus is deposited around the hutch and squashed against the rabbit's rear.

The usual culprits are familiar.

Too many pellets.

Pellets are convenient, palatable and easy to over-supply. A rabbit filling up on pellets eats less hay, which reduces fibre and wears the teeth less.

Muesli-style mixes.

The worst offender. A mix of flakes, pellets, grains and coloured pieces allows selective feeding, and rabbits reliably select the sugary, starchy parts and leave the fibrous ones. The result is a diet far richer than the label implies, and it is associated with both dental disease and caecotroph problems.

Treats.

Yoghurt drops, honey sticks, cereal bars, bread, breakfast cereal and biscuits. None of these belong in a rabbit's diet.

Too much fruit and root vegetable.

Carrot, apple and banana are sugar. They are occasional small treats, not daily items.

Not enough hay actually eaten.

Owners often provide hay and assume it is being eaten. Watch the hay rack, not the hutch floor.

Hay is the diet, not the bedding. A rabbit should eat a volume of hay each day roughly the size of its own body.

Cause two: the rabbit cannot reach

In this version the caecotrophs are normal. The rabbit simply cannot get to them.

Obesity.

The most common reason. A rabbit carrying too much weight cannot flex round to its anus, and a large dewlap makes it harder still.

Arthritis and spinal disease.

Common in older rabbits and frequently untreated. The rabbit is stiff, reluctant to move, may sit in one place, and cannot turn to groom. Pain relief prescribed by a vet often resolves the problem entirely, which is a striking result for something owners assume is dietary.

Dental disease.

A rabbit with painful cheek teeth cannot chew hay, cannot groom, and cannot comfortably take caecotrophs. Drooling, a wet chin, weight loss, reduced hay intake and one-sided eye discharge all point here.

Long coats.

Angoras and other long-coated rabbits collect caecotrophs in the fur even when they are behaving normally.

Sore hocks and foot pain.

A rabbit with painful feet cannot adopt the posture needed.

Illness and weakness.

Any unwell rabbit, and specifically rabbits affected by Encephalitozoon cuniculi, may be too weak or uncoordinated.

A bonded partner.

Worth knowing: a companion rabbit sometimes grooms the affected animal or eats the caecotrophs, which masks the problem until it becomes severe.

Tell the two causes apart by looking at what has been left behind. Well-formed, grape-like clusters that have simply been abandoned point to a rabbit that could not reach. Pasty, loose, poorly formed material points to a diet problem.

Fixing the diet without causing a crisis

Never cut pellets abruptly. A rabbit that suddenly loses a large part of its calorie intake may not immediately make it up with hay, and a rabbit that stops eating develops gut stasis, which is an emergency.

Increase hay first.

Offer several types and see which is eaten. Put it in more than one place, use a rack the rabbit can reach easily, and mix fresh greens into it to encourage foraging. The target is a volume of hay each day roughly equal to the size of the rabbit itself.

Then reduce pellets gradually.

Reduce the daily measured amount in small steps over several weeks, weighing the rabbit weekly and checking that hard pellet output stays plentiful.

Switch from muesli to a uniform extruded pellet.

Mix the new pellet into the old over one to two weeks so the rabbit cannot select against it.

Move treats out of the daily routine.

Fruit and root vegetables become occasional and small. Grain-based and sugar-based treats go entirely.

Keep greens.

A daily variety of leafy greens is part of the diet, not a treat, and it also increases water intake.

Weigh weekly and count droppings.

Hard pellets should stay plentiful, large, round and fibrous. Fewer or smaller pellets means the change is going too fast.

Daily care while you sort it out

Check the rear twice a day, every day, through warm weather, and at least daily the rest of the year. Lift the rabbit gently or, better, tip it just enough to see while it is supported on a stable surface.

Clean gently with warm water on cotton wool or a soft cloth, working the mess away rather than scrubbing.

Dry thoroughly. Damp fur attracts flies as reliably as soiled fur does. Pat dry with a towel, then finish with a hairdryer on the coolest setting held well away, if your rabbit tolerates it.

Trim carefully, or not at all. Rabbit skin is extremely thin and tears easily, and scissors used close to it cause serious wounds. If matting needs removing, a vet or an experienced rabbit groomer with clippers is the right answer.

Keep the environment dry and clean. Damp bedding, a soiled litter tray and a wet hutch all add to the problem.

Fit fly protection in summer: fine mesh over outdoor housing, prompt removal of soiled bedding, and a rabbit-specific preventive product discussed with your vet.

What never to do

Never bath a rabbit. Rabbits panic in water, and a struggling rabbit can fracture its own spine. Full immersion also causes chilling and shock, and the coat takes many hours to dry, which is exactly the condition flies are looking for.

Never use scissors close to the skin to remove matted fur.

Never use human wet wipes containing alcohol or fragrance.

Never stop pellets suddenly.

Never withhold food from a rabbit for any reason. Rabbits must eat continuously.

Never assume the problem is dietary in an older or overweight rabbit without having pain and mobility assessed.

Never use a dog or cat flystrike or flea product without checking that it is licensed for rabbits. Several are dangerous.

Never treat a rabbit producing no hard pellets at all as a diet problem. That is gut stasis and it is an emergency.

When to get help

Go the same day for a rabbit producing no droppings at all, for watery output with no hard pellets, for maggots or a wound at the rear, for a foul smell, or for a rabbit that has stopped eating.

Book an appointment this week for uneaten caecotrophs that persist after a genuine diet review, for any rabbit that is overweight, stiff, or reluctant to move, for drooling, a wet chin or reduced hay intake, and for one-sided eye discharge.

Ask specifically for a dental examination under sedation rather than a conscious look, and for a mobility and pain assessment in any rabbit over middle age. Pain relief is frequently the treatment that solves this, and it is frequently not offered because nobody connected a dirty bottom with a sore back.

Bring the exact diet with brand names and measured amounts, the weight history, photographs of what you found, the hay type and how much is eaten, and details of any companion rabbit and its diet, since the two usually eat from the same bowl.

A rabbit on a hay-first diet, at a healthy weight and free of pain, produces plenty of dry round pellets and no visible caecotrophs at all.

Measure the pellets rather than filling the bowl. The daily portion is small, and it is the part of the diet that most often needs reducing.