What the Eft? The Odd Life Cycle of the Eastern Newt
Have you ever seen one of these cute little guys swimming around in a pond before?
This is an eastern newt (Notophthalmus viridescens)! These amphibians are a type of salamander found throughout the eastern United States and Canada. You may find these guys in some Great Parks on the south side of Cincinnati, such as Woodland Mound and Shawnee Lookout. While I find these newts to be absolutely adorable, what I find most interesting about them is their odd life cycle. Before we get into that, let’s take a look at the average life cycle for an amphibian.
Amphibian Metamorphosis 101
The word “amphibian” comes from the Greek word amphibious, which means to lead a double life. Amphibians definitely live a double life, since they’re masters of water and land! Most species of amphibians follow the same basic life cycle: adults lay their eggs in water, the eggs hatch into larvae and those larvae transform into terrestrial adults. See the graphic below of a frog’s life cycle for reference.
This “transformation” amphibian larvae go through to become adults is called metamorphosis. In this process, animal larvae gain or lose body parts so that they can live as adults. As we see with our frog above, the tadpole grows legs to be able to live on land.
Unlike frogs however, newts live more than just a “double life.” Instead of their larvae going through metamorphosis straight to adulthood, newts go through an intermediate terrestrial stage and then become aquatic again as adults! How does this happen? Let’s take a closer look at their life stages.
Life Stage 1: Egg
Eastern newts begin life as aquatic eggs, like most amphibians. In the late winter to early spring, male newts actively court females through a dance of sorts by wiggling and waving his tail back and forth in the water. Once the female is ready to mate, the male will wrap his back legs around the side of the female, just below her forearms. This mating position is known as amplexus, and it is in this position the female can fertilize her eggs. As the female lays her eggs, she wraps each one carefully in the leaf of an aquatic plant. This takes her a while because she can lay 200 to 400 eggs each breeding season!
These eggs are a little different than the chicken eggs you have in your refrigerator. Instead of a hard shell that keeps the inside moist, amphibian eggs are coated in a jelly-like substance that feels like Orbeez (the child’s toy of super-absorbent, squishy spheres that grow when placed in water). Since these eggs do not have that hard shell, they must be kept moist in the water.
Life Stage 2: Aquatic Larvae
It only takes eggs three to eight weeks before they hatch into 1/4- to 1/2-inch olive green larvae. These guys look a little different than the frog tadpoles that most of us are familiar with. They have a keeled tail with four tiny legs and feathery external gills.
Since their mother abandons them after she lays the eggs, these larvae must quickly learn how to avoid predators. While small, these guys are also predators themselves, eating mostly aquatic insects. Newts generally remain as larvae for three to five months before they begin their metamorphosis in the fall.
Life Stage 3: Terrestrial Eft
After their first transformation, eastern newts enter what’s called the red eft stage. The red eft is easily recognizable with its bright orange coloring and rows of black-ringed spots. While that coloration may look pretty to us, it serves as a warning to other animals that these guys are not a tasty snack! Eastern newts are toxic to eat, especially during the eft stage when they are 20 times more toxic than at any other stage (“Eastern Newt”).
Unlike other salamanders that are nocturnal and live under logs, red efts can be found walking around in broad daylight. Their favorite habitats are forest floors with lots of leaf litter to hide in and to keep their skin moist. Remember, even terrestrial amphibians need to keep their skin moist!
Like their younger selves, efts primarily eat insects, but will also eat small snails. Instead of living in this stage for a few short months, efts live on land for several years, hibernating under rocks and logs during the cold winter months. Once they’re ready, the efts will make their way back to the water to undergo their final stage of metamorphosis.
Life Stage 4: Aquatic Adult
Adult eastern newts look quite a bit different from the efts. Instead of bright orange skin, theirs darkens to a nice olive green with a yellow stomach and lots of black polka dots. Their tails also broaden into that keeled shape like the larvae. This provides a nice rudder to help them swim along in their new environment. While they’re mostly aquatic, the adult newts can still live on land if necessary such as when their pond dries up. The adults still have lungs, but like most salamanders, they can also breathe through their skin.
As adults, newts still eat insects but will also eat pretty much whatever prey they can fit in their mouths – even other amphibian eggs! Among all three life stages (excluding the egg stage), eastern newts can live up to 15 years.
Now that you understand the basic life cycle of the newt, let me blow your mind a little bit. See, this is not the only life path that these guys can follow. It gets weirder. Let me explain.
Curiouser & Curiouser
We are taking a step back to Life Stage 2: Aquatic Larvae stage. Let’s say that our newt lives in a pond where food is abundant, there are no fish and it never dries up. However, the land outside the pond is not ideal to live in. This is true for some populations of eastern newt. In these cases, eastern newts can skip metamorphosis and mature to adulthood as larvae! So instead of looking like normal adults, these guys look like giant larvae that can reproduce. Similarly, eastern newts can also skip the second round of metamorphosis and become mature as terrestrial efts, only returning to the water to breed.
This phenomenon is called neoteny. Neotenic adults are animals that have held onto characteristics that are associated with young, immature animals. Other species of salamanders can also become neotenic. Many people today are familiar with axolotls, which are evolutionary descended from tiger salamanders. Neoteny is a brilliant survival adaptation. Instead of waiting several years to mature to reproductive age, being able to fast track sexual maturity helps the population thrive (Brown, 2021).
It’s important to recognize here that while neoteny does occur, it is a rare phenomenon. Scientists are not entirely sure what triggers newts and other salamanders to be neotenic. Populations that have this sort of life cycle tend to be in areas where the terrestrial habitat is challenging (Brown, 2021). The adaptation also protects against competition within the species: Instead of all the newts fighting for the same resources, if they live in different habitats then resources are more abundant.
In comparison to the frog life cycle we originally looked at, eastern newt life cycles are far more complex. Instead of one simple cycle, there are multiple paths newts can go down. The illustration above shows the many paths newts can take in their development.
I hope that this little insight into the odd life cycles of eastern newts helps you fall in love with them as I have. If you’re interested in learning more about amphibians, check out our calendar for programs and events all about amphibians.
Nature Interpreter, Woodland Mound
- Bohenek, Jason R., and William J. Resetarits. “Are Direct Density Cues, Not Resource Competition, Driving Life History Trajectories in a Polyphenic Salamander?” Evolutionary Ecology, vol. 32, no. 4, 2018, pp. 335–357., https://doi.org/10.1007/s10682-018-9941-8.
- Brown, Elizabeth Anne. “These Salamanders Live Their Lives, and Breed, as Babies.” National Geographic, National Geographic, 4 May 2021, https://www.nationalgeographic.com/animals/article/salamanders-newts-babies-metamorphosis-news.
- “Eastern Newt.” Connecticut’s Beardsley Zoo, https://www.beardsleyzoo.org/eastern-newt.html.