Salamanders are the only amphibians that have tails in the adult stage of their life. Their slender bodies and four short legs, give them a somewhat lizard-like appearance. But have you ever wondered why salamanders have long tails, when other amphibians, such as frogs, don’t?
Salamanders’ long tails serve many important functions. Salamanders use their tails to help them move through the water, for predator defense, to attract mates, and also for balance. Some salamander species use their tails as fat storage, which is crucial to help hibernate and make it through the winter.
Salamanders often lose, and regenerate their tails several times throughout their lives.
Salamanders’ tails have important functions
As mentioned above, salamanders use their tails for many purposes, from predator defense to mating. Here are a few things salamanders use their tails for.
1. Predator Defense
When salamanders are grabbed by a predator, they can break off their tails in a fraction of a second and escape.
This is known as autotomy (meaning “self-severing” in Greek), or self-amputation.
Salamanders are born with a line of weakness in their tail, called a fracture plane, which is the spot along the tail that is meant to break and release.
In some species, such as the four-toed salamander (Hemidactylium Scutatum), the fracture plane is visible as an obvious constriction at the base of the tail.
If a salamander is grasped by a predator, (particularly if grabbed by the tail), the muscles along the fracture plane pull away from one another in a reflex muscle spasm.
The pulling apart of the muscles causes the tail to break off at the fracture plane.
Once detached, the tail whips around and wiggles on the ground, for up to 5 minutes in some species.
The dropped tail distracts the predator, buying the salamander enough time to scurry away.
Salamander tail autotomy is so efficient that when the tail breaks off, the salamander suffers little to no blood loss.
2. Movement in the Water
Most salamanders (not all) develop in three life stages: Egg, larva, and adult.
Female salamanders lay eggs in shallow fishless ponds or other fishless water bodies.
With time, tiny larvae (baby salamanders) hatch from these eggs.
These larvae are fully aquatic have external feathery gills attached to either side of their head, and live entirely in the water, just like fish.
Over time, the larvae will go through a process known as metamorphosis in which they will transform into juveniles with features for a terrestrial life.
Once fully transformed, they will leave the water for a life on land, returning to the water to breed.
How Salamanders Use Their Tail to Swim
Both in the larval, and adult stages of their lives, salamanders rely on their tail to move through the water.
Salamander larvae have tiny hind legs and a flat paddle-like tail fin. They swim by flapping their tail from side to side and are excellent swimmers.
Adult salamanders spend most of their lives on land and return to the water. This means their features are mostly adapted for life on land rather than in the water.
Still, they are very strong swimmers.
Adult salamanders swim by tucking their legs against the side of their body and making winding movements with their whole body with the tail flapping from side to side – very similar to how crocodiles or alligators swim.
3. Fat Storage
Vertebrates primarily store energy in their adipose tissue.
In salamanders, energy reserves can also be stored in the adipose tissues of the tail.
These energy reserves are essential for salamanders to hibernate and make it through the winter.
As winter approaches, salamanders instinctively know to start preparing for hibernation.
Most salamanders will start to eat more than normal, to put on good body weight before they enter hibernation.
A significant amount of these extra proteins and fats are stored in the tail.
After bulking up, salamanders will voluntarily stop eating, and rely on their energy reserves to survive the winter.
4. Mating Dances
The vast majority of salamander species reproduce via internal fertilization.
In many species, the male performs a mating dance for the female before dropping an external sperm sac which the female must “pick up” with her cloaca to fertilize her eggs internally.
The mating dance often involves the use of the tail. For this reason, losing a tail could result in a reduced ability to locate mates.
5. Balance and Better Maneuverability
Salamanders use their tails to offset their center of mass, giving many species mass to throw to one side or the other for better maneuverability and turning.
Most salamanders are less maneuverable when they lose their tails.
Salamanders Sometimes Live Without Their Tails
When a salamander loses its tail, it often takes a few months for a replacement tail to develop.
During this period, the salamander will live without a tail.
Over time, stem cells in the spinal cord enable it to regenerate a tail that closely mimics the original.
Since salamanders lose not only flesh but also nerves when they drop their tails – nerve axon regeneration happens at the same appearance as tissue, bone, and muscle regeneration.
It is not uncommon to find salamanders in the wild with a partially regenerated tail.
In many salamander species, the tail that grows back is often lighter in color than the original tail.
A single salamander can drop and regenerate a few tails in its lifetime.
Salamanders are known to be able to regenerate limbs after an injury throughout their lives.
When a salamander loses its tail, it will always regrow a new one.
Conclusion
Salamanders have long tails for several purposes, including balance, defending against predators, and energy storage.
That said, most salamanders can lose their tails and survive perfectly fine until they regenerate a replacement tail.
Sources:
Wake DB, Dresner IG. Functional morphology and evolution of tail autotomy in salamanders. (PDF).
Elad Bassat, Elly M. Tanaka, The cellular and signaling dynamics of salamander limb regeneration, Current Opinion in Cell Biology, Volume 73, 2021, Pages 117-123, ISSN 0955-0674, https://doi.org/10.1016/j.ceb.2021.07.010.