Reptile brumation and hibernation: the pre-season check and the mistakes that kill

Quick answer

A reptile in good condition, feeding well and holding its weight, is the only kind that should be cooled for a season

Every autumn, two opposite mistakes are made with pet reptiles. Temperate species are kept artificially warm and never allowed the seasonal slowdown their physiology expects. Tropical species are cooled by owners who believe all reptiles hibernate, and some of them do not survive it.

Getting this right starts with a single question: does your species do this at all in the wild, and is this individual healthy enough to attempt it.

• Mediterranean tortoises hibernate. African tortoises such as sulcata, leopard and pancake tortoises do not, and cooling them is dangerous.
• Tropical species including chameleons, crested geckos and most pythons should never be deliberately cooled.
• The gut must be empty before cooling. Food left in a cold gut does not digest, it rots.
• An animal that is underweight, dehydrated, has any nasal or eye discharge, or has an untreated parasite burden must not be cooled at all.
• A reptile that urinates during hibernation has lost its water reserve and must be woken and rehydrated.

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Never cool a reptile that is not fully healthy.

Immune function in a reptile falls with body temperature. A cool animal cannot fight infection, so a mild respiratory infection, an untreated parasite burden or a mouth problem that was manageable in September becomes life-threatening by February. Every serious hibernation loss traces back to an animal that went into the cold with something already wrong.
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Decide in 60 seconds

Brumation is not hibernation, and neither is sleep

Mammal hibernation involves an actively regulated drop in body temperature and metabolism, driven from the inside.

A reptile has no internal thermostat to turn down. Its metabolic rate simply falls as its body temperature falls, and that fall is imposed by the environment. Shortening days and dropping temperatures cue the behavioural change, the animal stops feeding, seeks shelter and becomes inactive.

Three practical consequences.

The animal is not unconscious. It can move, and it will, occasionally. Movement in itself is not an alarm.

It still loses water. Dehydration, not starvation, is the usual cause of death during a reptile winter. This is why hydration before, during and immediately after matters more than fat reserves in most cases.

Temperature is the entire control system. A little too warm and the animal burns reserves at a rate it cannot sustain, without being warm enough to digest or drink normally. That in-between zone is the most dangerous place to leave a hibernating reptile.

Which species, and which absolutely not

Two rules cover most confusion. Where the species comes from decides the answer, not the fact that it is a reptile. And a species that does brumate in the wild does not have to be brumated in captivity, if the animal is not in a fit state for it.

Should you brumate at all?

For temperate species there is a genuine argument on both sides, and it is worth understanding rather than following a rule.

In favour. It is part of the annual cycle these animals evolved with. It is required for normal reproductive cycling in most temperate species. Many keepers report better long-term condition in animals given a proper seasonal rest.

Against. It carries risk, and the risk falls almost entirely on animals that were not fit to start. A first-year hatchling has minimal reserves. An animal with an undiagnosed problem will get worse in the cold, not better.

The workable position is this: a healthy adult of a temperate species can and generally should be given a cool season. A juvenile, an underweight animal, or one with anything unresolved should skip it, and skipping it does no harm.

The pre-season check

This is the part that decides the outcome, and it happens weeks before anything gets cold.

Hydration, weight and a proper look at the animal before the season starts are worth more than anything you can do once it is cold

Why a runny nose disqualifies an animal absolutely.

Nasal discharge in a tortoise is not a cold. It indicates disease of the upper airway that a warm animal is holding at bay with an active immune system. Cool that animal for months and the infection has a free run at it. Animals with nasal discharge hibernated anyway are among the most common losses.

Why weight matters in both directions.

Too light and there is nothing to live on. Unusually heavy for the size of the animal can indicate fluid, a mass or eggs rather than good condition, which is why a vet's opinion beats a number on its own.

Emptying the gut, and why it is not optional

At normal temperatures a reptile digests food and passes waste. At hibernation temperatures digestion effectively stops.

Food left in the gut when the animal cools does not sit inert. It ferments and decomposes, producing gas and bacterial overgrowth in a gut whose owner cannot move it along and whose immune system is switched down. The result is a severely ill or dead animal partway through the winter.

The process.

Stop feeding while keeping the animal at full normal temperature and lighting. It must stay warm enough to complete digestion and pass everything through.

Continue until droppings have stopped completely. That is the endpoint, not a date on a calendar. A large tortoise takes considerably longer than a small one, and a cool autumn room lengthens it further.

For tortoises, daily warm shallow baths during this period encourage drinking and passing waste. The water should be shallow enough that the animal's head is clear at all times.

Only once the gut is empty and the animal is well hydrated does the cooling begin.

Cooling down and running the season

Ramp, do not switch.

Reduce temperature and day length gradually over a period of weeks. An abrupt drop is a shock, and shock in a reptile causes exactly the kind of stress response that suppresses immunity.

The target range is species specific and narrower than people expect.

Too warm and the animal burns reserves without being able to eat or properly drink. Too cold and tissue freezes, with permanent eye damage being a documented consequence in tortoises. Get the correct range for your exact species from a reptile vet or a species specialist, and verify it with a thermometer that has a probe and a minimum and maximum memory.

Where.

The two common approaches for tortoises are a controlled refrigerator dedicated to the purpose, and an insulated box within a box in an unheated but frost-free space. A dedicated fridge gives stable temperature and is the more reliable of the two, provided the door is opened daily for air exchange and the temperature is logged.

An unheated garage or shed relying on outdoor weather is the least controllable option, and it is where most temperature accidents happen.

Protect against rodents.

A hibernating tortoise cannot defend itself. Rats and mice will gnaw at limbs and shell. The container must be genuinely rodent-proof, not merely covered.

Monitor without disturbing.

Weigh weekly, quickly and gently. Log the temperature daily. Look for wet or soiled bedding at each check.

Weight should fall only very slowly across the whole season. A brisk fall means the animal is too warm or is unwell, and the correct response is to wake it rather than to adjust and hope.

The urination alarm.

A hibernating tortoise that urinates has lost the water reserve it was relying on. This is one of the clearest reasons to end hibernation immediately, warm the animal up and rehydrate it. Do not put it back.

Bearded dragon brumation, and telling it from illness

Condition, colour and alertness are what separate a brumating reptile from an unwell one

Bearded dragon brumation looks alarming to a first-time owner. The dragon hides, buries itself, sleeps for days at a time, ignores food and may not emerge for weeks.

The safe approach with a dragon that appears to be brumating is to measure the enclosure temperatures first, weigh weekly, leave a shallow water dish available, offer a bath occasionally for hydration, and leave the animal alone otherwise.

Do not force feed a brumating dragon. It is not starving, and handling it repeatedly is the fastest way to turn a normal season into a stress problem.

Weight loss, discharge, laboured breathing or an animal that cannot be roused are all reasons to end the assumption and see a vet.

Waking up

Warm it properly and quickly enough.

Bring the animal back to full normal temperatures over a day or so. A half-warmed reptile is in the worst place possible: awake enough to use energy, not warm enough to digest.

Rehydrate first, feed second.

For tortoises, warm shallow baths from the first day. Drinking is the priority. Appetite generally follows hydration.

Restore full lighting immediately.

Correct temperature and correct ultraviolet output from day one. This is one of the main determinants of whether the animal starts eating.

Expect eating to resume within a reasonable window, and act if it does not.

A tortoise that has woken, is warm, is being bathed, has proper lighting and is still not eating after a couple of weeks has post-hibernation anorexia. This is a recognised problem with real causes behind it, including dehydration, liver stress, mouth disease and infections that were present before hibernation. It needs a veterinary appointment rather than more patience.

Weigh, and keep weighing.

Compare against the pre-hibernation weight. Recovery of weight over the following weeks is the measure of whether the season went well.

What never to do

Do not hibernate a sulcata, leopard, red-footed or yellow-footed tortoise, or any tropical species.

Do not cool an animal with any nasal or eye discharge, however mild.

Do not cool an animal that has not fully emptied its gut.

Do not hibernate a hatchling in its first year without species-specific advice.

Do not rely on the outdoor weather to set the temperature.

Do not check on a hibernating animal by handling it repeatedly. Weigh weekly and otherwise leave it.

Do not put an animal that has woken, urinated or lost weight rapidly back into hibernation.

Do not force feed a brumating reptile.

Do not skip the post-hibernation weight recovery check because the animal is eating again. Eating a little is not the same as regaining condition.

When to get help

A reptile that has come through the season warm, hydrated and back on food is what the whole process is aiming at

See a reptile vet before the season starts, not after it. The pre-hibernation examination and faecal screen prevent most of the disasters described here.

Contact a vet during the season for rapid weight loss, urination, a wet or soiled box, discharge from the nose or eyes, or an animal that cannot be roused.

Contact a vet after waking if the animal is not drinking, is not eating within a couple of weeks of being fully warm and lit, or has not started to regain weight. Post-hibernation anorexia has causes that are treatable, and the sooner they are found the better the animal does.