San Marcos salamander facts for kids

Quick facts for kids San Marcos salamander
Conservation status
Vulnerable (IUCN 3.1)
Threatened (ESA)
Scientific classification

The San Marcos salamander (Eurycea nana) is a small, special kind of salamander that lives only in water. It doesn't have lungs like humans do, but breathes through its skin and gills. This salamander is found only in a small area of the San Marcos River in Hays County, Texas, USA. It's usually about one to two inches long, has a thin body, and is reddish-brown with gills on the outside of its body.

What Does the San Marcos Salamander Look Like?

The San Marcos salamander, known scientifically as Eurycea nana, lives its whole life in water. It never leaves the water to live on land. This means it keeps its gills, which help it breathe underwater, for its entire life.

This salamander has a narrow head with a rounded nose and big, dark eyes. Its gills are easy to see and have color. The salamander is light brown all over, with seven to nine light spots along its back. Its belly is white. Males have larger vents than females. It has four toes on its front feet and five on its back feet. The longest San Marcos salamander ever measured was about 56 millimeters (about 2.2 inches) long.

Downstream from the headwaters of the San Marcos Springs

San Marcos Salamander Family Tree

The name nana comes from a Greek word meaning "dwarf," because these adult salamanders are very small. The San Marcos salamander belongs to a group of salamanders called Plethodontidae, which are known as "lungless salamanders." This means they don't have lungs and breathe through their skin and gills instead.

Sometimes, people might confuse E. nana with another salamander called Eurycea neotenes. However, the San Marcos salamander is smaller and has a thinner body.

Where Do San Marcos Salamanders Live?

The only place in the world where the San Marcos salamander lives is the San Marcos River in Hays County, Texas. In 1973, scientists thought there were about 20,880 salamanders living in the upper part of Spring Lake. By 1993, the number was estimated to be around 30,451 salamanders throughout Spring Lake and a short distance downstream. The number of males and females seems to stay balanced throughout the year.

What is Their Home Like?

The San Marcos salamander needs clear, flowing spring water to live. The water in the San Marcos River stays at a temperature of about 21 to 22 degrees Celsius (70 to 72 degrees Fahrenheit). If the water gets hotter than 30 degrees Celsius (86 degrees Fahrenheit), the salamanders start to get stressed. Young salamanders are even more sensitive to hot water than adults.

These salamanders are often found among rocks and plants at the bottom of the river. The shallowest part of Spring Lake has sand, gravel, and big limestone rocks, which are perfect places for them to live. Further down, there are concrete banks and rocks where aquatic moss and blue-green algae grow. Many other water plants are also found here. Areas without plants or with muddy bottoms are not good for the salamanders. This is because plants and rocks help protect them from predators like bigger fish, turtles, and water birds.

What Do San Marcos Salamanders Eat?

The San Marcos salamander eats small water creatures like amphipods (tiny shrimp-like animals), fly larvae (baby flies), and aquatic snails. Their diet changes depending on what small creatures are available at different times. They rely on where these creatures are and when they are active. The plants around them provide a lot of food.

How Do San Marcos Salamanders Behave?

San Marcos salamanders have special ways to avoid predators. They can sense chemicals released by predators like the Largemouth bass. When they sense danger, they might freeze to avoid being seen. They also tend to return to the same safe spots, which helps them stay hidden from predators. Studies show that salamanders who haven't met predators before might hide more than those who have. This means they can learn and change their behavior. They can also recognize new predators that are similar to the ones they know.

When a San Marcos salamander eats, it waits for its prey to swim by. Then, it quickly snaps forward to catch its food. This suggests they use their sight or feel vibrations in the water to find their meals.

San Marcos salamanders lay their eggs in still ponds within thick mats of water plants. The eggs are covered in jelly and hatch in about 24 days. Male salamanders are ready to reproduce when they are about 19 millimeters (0.75 inches) long from their nose to their vent. Females are ready when they are about 26 millimeters (1 inch) long. Females can lay many eggs, possibly up to 176 eggs per year. Both male and female salamanders can tell the difference between each other, which helps them find mates. This is a rare behavior among salamanders.

The San Marcos salamander can change the color of its back from light tan to dark brown. This helps them blend in with their surroundings, depending on how light or dark the river bottom is. Their gills also change color based on how much oxygen is in the water. They look bright red when there's not much oxygen, and can even shrink if the water has a lot of oxygen.

Why Are San Marcos Salamanders Important to Protect?

The San Marcos salamander has been listed as a threatened species since 1980. This means it's at risk of disappearing. Because it lives in such a small area, its biggest threats are pollution of the groundwater and how much water cities in central Texas use from the Edwards Aquifer. Other dangers include the springs drying up and new species being introduced that might harm them. Since they can't move to new places, they can't naturally get new genes if their current population loses its variety. Having enough food is also a concern, but not as much as losing their habitat.

There is a plan called the San Marcos/Comal (Revised) Recovery Plan from 1996. This plan aims to protect the salamander and four other species. It includes goals like keeping the aquifer healthy and finding ways to solve problems related to their recovery. Scientists have also tried to breed San Marcos salamanders in aquariums. In these efforts, about 30% of the eggs hatched.

What Diseases Can San Marcos Salamanders Get?

Sometimes, San Marcos salamanders in captivity have been found with a curved spine, a condition called Kyphosis. This is caused by tiny parasites.

A fungus called Batrachochytrium dendrobatidis has also been found in San Marcos salamanders. This fungus is a big threat to amphibians around the world. It causes a disease that can lead to death in salamanders and has caused many species to disappear since it was discovered.

Images for kids

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  Downstream from the headwaters of the San Marcos Springs