Brumation Explained

Brumation Explained: What It Is, Why It Happens and Which Animals Experience It

When winter arrives in Britain, many animals disappear from view. Hedgehogs hibernate, some birds migrate, and countless insects survive in sheltered locations until warmer weather returns.

But what happens to reptiles and amphibians?

Many people assume they simply hibernate like mammals. In reality, most cold-blooded animals undergo a different process known as brumation.

Brumation is a natural period of dormancy that allows reptiles and some amphibians to survive cold weather when food is scarce and temperatures are too low for normal activity. Although it shares similarities with hibernation, there are several important differences.

This guide explains what brumation is, how it differs from hibernation, which British animals experience it, and why this remarkable adaptation is essential for the survival of many cold-blooded species.

What Is Brumation?

Brumation is a state of seasonal dormancy entered by many reptiles and some amphibians during colder months.

As temperatures fall, these animals become much less active because they rely on external heat sources to regulate their body temperature. Their metabolism slows dramatically, allowing them to survive long periods with little or no food.

Unlike mammals in hibernation, animals in brumation may occasionally wake, move around, or drink water before returning to their dormant state.

In simple terms:

- Mammals generally hibernate.

- Reptiles generally brumate.

Although the two processes are similar, they are not identical.

Why Do Animals Brumate?

Reptiles are ectothermic, meaning they depend on environmental heat rather than producing enough body heat to remain active during cold weather.

As temperatures decline:

- Digestion becomes inefficient.

- Muscles work less effectively.

- Hunting becomes difficult.

- Food becomes scarce.

- Growth slows.

- Energy demands decrease.

Rather than continuing to search for food they cannot efficiently digest, reptiles conserve energy by entering brumation.

This strategy greatly increases their chances of surviving the winter.

How Is Brumation Different from Hibernation?

The terms are often used interchangeably, but they describe different biological processes.

Hibernation

Hibernation occurs mainly in warm-blooded mammals.

During hibernation:

- Body temperature drops significantly.

- Heart rate slows dramatically.

- Breathing becomes much slower.

- Animals remain deeply asleep for extended periods.

Examples include:

- Hedgehogs

- Dormice

- Some bats

Brumation

Brumation occurs mainly in reptiles.

During brumation:

- Metabolism slows.

- Activity is greatly reduced.

- Body temperature follows the surrounding environment.

- Animals remain capable of waking if conditions improve.

Rather than sleeping continuously, reptiles often remain quietly sheltered until warmer weather returns.

Which Animals Experience Brumation?

Brumation is most common among reptiles.

UK Species that may brumate include:

- Snakes

- Lizards

Outside of the UK:

- Tortoises

- Turtles

- Crocodilians (when in cooler regions)

Some amphibians also undergo similar periods of winter dormancy.

These include:

- Frogs

- Toads

- Newts

- Salamanders

The exact behaviour varies between species.

British Animals That Brumate

Several native reptiles and amphibians survive winter through brumation.

Grass Snake

The grass snake, Britain's largest native snake, spends winter hidden beneath:

- Log piles

- Compost heaps

- Rock crevices

- Mammal burrows

- Tree root systems

Individuals often emerge during mild winter spells before returning to shelter.

Adder

Britain's only venomous snake also brumates. Adders frequently return to the same underground hibernaculum each year. Several snakes may share the same winter refuge.

Smooth Snake

Found mainly on southern heathlands, smooth snakes spend winter in underground shelters where temperatures remain relatively stable.

Slow Worm

Although often mistaken for snakes, slow worms are legless lizards. They spend winter beneath rocks, compost heaps, and underground cavities where freezing temperatures are less likely.

Common Lizard

Britain's only widespread egg-laying lizard reduces activity as temperatures fall and shelters beneath vegetation or underground.

Common Frog

Although frogs are amphibians rather than reptiles, many spend winter in sheltered locations beneath logs, leaf litter or at the bottom of ponds.

Their winter dormancy resembles brumation more closely than mammalian hibernation.

Common Toad

Common toads often overwinter in burrows, dense vegetation or beneath stones until spring breeding begins.

Where Do Animals Brumate?

Choosing the right shelter is critical.

Ideal brumation sites remain:

- Cool

- Moist

- Frost-free

- Undisturbed

- Protected from predators

Common locations include:

- Mammal burrows

- Rock crevices

- Tree roots

- Compost heaps

- Old walls

- Hollow logs

- Leaf litter

- Underground chambers

The temperature remains far more stable underground than above ground.

What Happens During Brumation?

As temperatures fall, reptiles gradually reduce their activity.

Several physiological changes occur:

- Metabolism slows.

- Heart rate decreases.

- Digestion stops.

- Feeding ceases.

- Growth pauses.

- Energy reserves are used slowly.

Unlike mammals in deep hibernation, reptiles may occasionally become active during unusually warm winter days.

They sometimes leave shelter briefly to:

- Drink water

- Change position

- Seek better temperatures

Once conditions cool again, they return to dormancy.

How Long Does Brumation Last?

In Britain, brumation typically lasts from:

October or November until March or April

The exact timing depends on:

- Species

- Latitude

- Local weather

- Habitat

- Annual climate variation

Mild winters may shorten the period considerably.

Do Pet Reptiles Brumate?

Many captive reptiles retain their natural instinct to brumate.

Examples include:

- Bearded dragons

- Corn snakes

- Leopard geckos (to a lesser extent)

- Hermann's tortoises

- Horsfield's tortoises

Even when kept indoors, seasonal changes in daylight and temperature may trigger reduced appetite and activity.

Owners should never deliberately induce brumation without understanding the specific requirements of their species. Animals should always be healthy before entering dormancy.

Is Brumation Dangerous?

Brumation is a normal and essential process.

However, risks include:

- Freezing temperatures

- Flooding of shelters

- Disturbance by humans

- Predation

- Dehydration

- Disease

Climate change may also alter winter temperatures, causing animals to wake too early when food remains scarce.

Can You Wake a Brumating Animal?

It is possible, but best avoided.

Repeated disturbance forces the animal to use valuable energy reserves needed to survive the winter.

If you discover a reptile sheltering during winter:

- Observe from a distance.

- Avoid handling.

- Leave shelters undisturbed whenever possible.

This gives the animal the best chance of surviving until spring.

Why Is Brumation Important?

Without brumation, many reptiles simply could not survive temperate winters.

The process allows them to:

- Conserve energy.

- Avoid starvation.

- Survive prolonged cold.

- Synchronise breeding with spring.

- Maximise survival until favourable conditions return.

It is one of the key evolutionary adaptations that has enabled reptiles to occupy cooler climates.

Helping Wildlife Through Winter

Gardeners can support brumating wildlife by creating safe overwintering habitats.

Helpful features include:

- Log piles

- Compost heaps

- Rockeries

- Dense vegetation

- Leaf piles

- Untidy corners

- Wildlife ponds

Avoid disturbing these areas during winter whenever possible.

Fascinating Facts About Brumation

Here are some surprising facts:

- Several reptiles may share the same winter shelter.

- Grass snakes sometimes brumate alongside slow worms and amphibians.

- Adders often return to the same hibernaculum year after year.

- Reptiles usually stop eating before brumation because food cannot be digested efficiently in cold conditions.

- Some amphibians can tolerate partial freezing of body tissues while overwintering.

- Mild winter weather may briefly interrupt brumation before animals return to shelter.

Frequently Asked Questions

What is brumation?

Brumation is a period of winter dormancy in reptiles and some amphibians during which metabolism slows and activity is greatly reduced.

Is brumation the same as hibernation?

No. Hibernation occurs mainly in warm-blooded mammals, while brumation occurs primarily in cold-blooded reptiles. Animals in brumation may occasionally wake and move about during mild weather.

Which UK animals brumate?

Britain's native reptiles—including grass snakes, adders, smooth snakes, slow worms and common lizards—undergo brumation. Several amphibians also enter similar winter dormancy.

Do reptiles sleep throughout brumation?

Not continuously. They often remain inactive for long periods but may briefly wake to drink water or move to a more suitable location.

Can climate change affect brumation?

Yes. Warmer winters may cause reptiles to emerge earlier than usual, potentially exposing them to late frosts or periods when food is still scarce.

Final Verdict

Brumation is one of Nature's most effective winter survival strategies.

Rather than hibernating like mammals, reptiles and many amphibians respond to falling temperatures by entering a state of reduced activity that conserves energy until spring.

Although the process resembles hibernation, important differences in physiology and behaviour make brumation a distinct adaptation.

Across the UK, grass snakes, adders, slow worms, common lizards and several amphibians rely on this seasonal dormancy to survive the colder months.

By understanding brumation—and by protecting the log piles, compost heaps and other sheltered habitats these animals depend upon—we can help ensure that Britain's native reptiles and amphibians continue to thrive for generations to come.

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