It’s common to encounter salamanders and other amphibians during the wet, warm season, but they seem to disappear during the winter. So how do these creatures survive the winter?
Salamanders survive the winter by hibernating. Terrestrial salamanders hibernate in logs or underground burrows below the frost line. Many aquatic salamanders hibernate by burying themselves in the mud at the bottom of the water bodies they are in.
That said it is important to note that “hibernate” is an inaccurate term. The correct term is “brumation”.
Hibernation is a term reserved for warm-blooded (endothermic) animals such as squirrels. Brumation refers to almost the same thing but in cold-blooded animals.
Brumation vs Hibernation
Brumation is very similar to hibernation. In fact, many people use these two terms almost interchangeably. However, there are some differences between these two concepts.
The Differences Between Hibernation and Brumation
Hibernation |
Brumation |
| Hibernation is voluntary | Brumation is involuntary |
| Hibernating animals still require lots of oxygen | Brumating animals have extremely low oxygen requirements. |
| Hibernating animals are not easily disturbed by temperature fluctuations and sleep through most of the winter | Brumating animals are easily disturbed by fluctuations in temperature and will be active on warm days in the winter |
Hibernation is when an endotherm (warm-blooded animal) such as a squirrel voluntarily reduces its activity and lowers its metabolism to conserve energy when sufficient food is not available.
During hibernation, the body temperature falls, and the heart and breathing rate slow down. Think of it like going into a very deep sleep for an extended period.
Brumation, on the other hand, is when an ectotherm (cold-blooded animal) such as a salamander or toad involuntarily enters a state of dormancy when the temperatures fall.
Cold-blooded animals cannot regulate their internal body temperature, so they are forced into dormancy when the temperatures fall. If they were to be active, they would freeze solid and die.
A significant difference between hibernation and brumation is the oxygen requirements of the animal.
Although hibernating animals have reduced oxygen requirements, they still need lots of oxygen to survive. In contrast, brumating animals have extremely low oxygen requirements.
Also, hibernating animals sleep through most of the winter (although to do occasionally wake up).
Brumating animals on the other hand will be active on warm days of the winter. If the weather is mild, they may come out of dormancy and bask in the sun before re-entering dormancy. Even if happens in the dead of winter.
However, despite these differences, I will stick to the well-known term “hibernation” to keep things simple. When I use the word “hibernation”, you know I really mean “brumation” ;).
Most Terrestrial Salamanders Hibernate Underground
Since there are so many salamander species. The exact place salamanders will hibernate differs among different species.
Most terrestrial salamanders will hibernate in underground burrows, where the frost does not penetrate.
Since they can’t dig their own burrows, they typically search for natural holes or abandoned mammal burrows that are deep enough that the frost does not penetrate all the way to the bottom.
Some Terrestrial Salamanders Hibernate Above-Ground
Rather than hibernating underground, some salamanders will spend the entire winter above ground. This could be in old tree stumps, in deep leaf litter, or under rocks, logs, and log piles in wet areas.
Salamanders in urban areas will sometimes seek out foundations where cracks exist and squeeze their way down into those crevices.
The most ideal hibernaculum (hibernating space) is somewhere moist that stays frost-free all winter. It shouldn’t be warm, it should just be protected from the frost.
Aquatic Salamanders Hibernate Underwater
Aquatic salamanders need to be in the water to survive, so they will only hibernate in an aquatic environment.
However, not just any pond will do, the pond needs to be deep enough so it does not freeze all the to the bottom.
It also needs to have lots of dissolved oxygen so the salamander can efficiently breathe underwater all winter long.
Unlike most other animals, salamanders do not burrow down into the mud when they hibernate underwater.
This is because salamanders breathe by absorbing oxygen that comes in contact with their skin. So if their skin is buried in mud, their breathing is obstructed.
Some salamanders may even occasionally swim around in the water during hibernation.
Some Aquatic Salamanders Stay Active Through the Winter
Although most salamanders hibernate, some aquatic salamanders such as the Common mudpuppy (Necturus maculosus) are active all winter.
When the temperatures drop, they just travel to deeper water, where the water doesn’t freeze solid.
Hellbenders (Cryptobranchus alleganiensis) overwinter in fast-flowing streams that remain ice-free all winter.
However, most aquatic salamanders, even if active in the winter, will wait until spring to mate and lay their eggs.
Spring Temperatures Bring Salamanders Out of Hibernation
When the snow starts to melt and the weather gets warmer, salamanders will emerge from hibernation. This is because their metabolic rates get high enough to allow them to be more active.
During this time, terrestrial salamanders will migrate to vernal pools and breeding ponds looking for mates.
After mating, the female salamanders will lay dozens of jelly-covered eggs and attach them to grass and other vegetation in the breeding ponds.
After a few weeks, tiny larvae will hatch from these eggs, and live an entirely aquatic life until they go through a process known as metamorphosis and transform into young versions of the adults.
These juvenile salamanders then leave the water, to live a mostly terrestrial life, only occasionally returning to the water.
What to Do if You Find a Hibernating Wild Salamander
If you find a hibernating salamander, it’s best to leave it alone. Do not touch it, pick it up, or move it to another location. Disturbing a hibernating amphibian could cause it to prematurely come out of hibernation, which can be fatal to the animal.
However, if you have already disturbed the salamander, there are several things you can do to improve its chances of survival.
The first thing to do is to put it back where you found it. If you forget the exact place it was or are otherwise unable to put it back where you found it, place it somewhere where it will be protected from frost and predators such as cats or owls.
This could be in a log pile, in a compost heap, or in any other safe area. The hibernaculum (hibernating place) you chose shouldn’t be warm, it should just be protected from the frost.
Not All Salamanders Survive the Winter
Sometimes, salamanders do not find a suitable overwintering site on time, and they are exposed to freezing winter temperatures, which is usually fatal to them.
Some salamanders do find overwintering sites, but then the frost penetrates all the way through, which exposes the hibernating amphibians to freezing temperatures.
Also, sometimes salamanders emerge out of hibernation too soon. This usually happens when they are disturbed from their state of hibernation by humans or other animals.
Sometimes, it also happens because of sudden weather changes – salamanders may be tempted out of their hibernating spots by an early warm stretch, followed by a quick drop in temperatures below freezing. This is known as winterkill.
Conclusion
Salamanders have a wide range of adaptations to survive harsh conditions.
The exact place a salamander will retreat to in the winter depends on the species and available areas within their habitats.
If you find a hibernating salamander, you best leave it alone! When the warmer spring temperatures come, it will wake from hibernation and walk out of its hibernating spot all on its own.