What's the difference between a newt and a salamander?

If you spot a small, long-tailed amphibian near a forested pond, you are likely looking at a salamander or a newt.

But what's the difference between a salamander and a newt? And how do you tell them apart?

"It's one of those things where all newts are salamanders, but all salamanders aren't newts," Nick Burgmeier, a research biologist at Purdue University, told Live Science.

Within the tree of life, salamanders are a large and diverse group of tailed amphibians. "They are the order Caudata, which literally means 'tailed' in Latin," said Karen Kiemnec-Tyburczy, an associate professor at California State Polytechnic University, Humboldt who specializes in salamanders. There are a total of 10 families of salamanders, she said. Newts are a subfamily called Pleurodelinae, within the Salamandridae family.

Since all newts are salamanders, there isn't really a distinct characteristic that separates one from the other. However, some species in the newt subfamily possess a few interesting traits, Burgmeier said. For example, a number of newts have warty, bumpy-looking skin. "They tend to have rougher skin," Burgmeier said, as opposed to salamanders' smooth, slimy skin.

This is likely because newts are the most toxic salamanders; their skin contains many poison glands. For instance, the skin of a rough-skinned newt (Taricha granulosa), a species found in western North America, has bacteria that secrete tetrodotoxin. It's the same toxin found in Japanese pufferfish and can be fatal if ingested.

"It would be pretty catastrophic if you happen to throw one in your mouth," Burgmeier said.

Further, salamanders in general have a "biphasic" lifestyle, Burgmeier noted, which means they often start the beginning of their life in water and then move on to land. With some newts, this life cycle can be "triphasic," which means they start their life in the water, have a juvenile "eft" phase in which they go onto land, and then end adulthood back in the water.

An example of this is the eastern newt (Notophthalmus viridescens), a common species in the eastern U.S. The newt has a characteristic bright orange juvenile that roams the forest floors (called a red eft). The efts live on land for around two to three years, equipped with developed lungs and toxins to ward off predators, before eventually metamorphosing into an aquatic adult.

However, interestingly, some coastal populations of eastern newts will skip their eft stage completely, spending their entire life underwater. And variations in lifecycles are common among newts and salamanders. Many newts in Europe and Asia have a more traditional biphasic lifestyle rather than the triphasic, Burgmeier said.

Similarly, not all newts have bumpy, toxic skin. Many, like the smooth newt (Lissotriton vulgaris), have smooth skin.

One reason for the lack of unifying newt traits is likely that when herpetology began, naming wasn't standardized.

"The term 'newt,' historically, was used informally as a common name for these sort of warty, bumpy [salamanders]," Kiemnec-Tyburczy told Live Science. "But it turns out that they are not each other's closest relatives. As salamander taxonomy became clearer throughout the 20th century, scientists classified the warty, bumpy salamanders and their closest relatives as newts. As a result today's subfamily hosts a hodgepodge of characteristics.

Diversity also abounds in the salamander order. There are lungless salamanders that have no larval stage at all; they develop inside the egg. Some salamanders, axolotls, never develop past their tadpole stage. Around the world, salamander species can also range from an inch (2.5 centimeters) to up to 6 feet (1.8 meters) long.

Salamanders are “just super cool," Burgmeier said. He studies the eastern hellbender (Cryptobranchus alleganiensis alleganiensis), the largest salamander in North America. Their presence and health can tell scientists a lot about water quality. For the smaller newts and salamanders, they can be a key part of the food web, eating invertebrates and supporting aquatic and terrestrial ecosystems alike, Burgmeier added.

"Salamanders have a ton of different things going on," Kiemnec-Tyburczy said. "Newts are just a small subset of all of the diversity within salamanders."

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