Salamanders secretively live deep in forests. They are no longer than 20cm, have four legs and a long tail and are covered with mucus. This amphibian has a somewhat humorous and cheerful appearance, yet it is extremely difficult for even experts to catch sight of them in nature. They are most often seen gathering at waterfronts to spawn during the breeding season, however very little is known of their lifestyle at any other time, including where they live and what they eat. About 20 species of salamander have been discovered in Japan and there are 500 throughout the world, although it is still uncertain exactly how many species there are.
Yukihiro Kohmatsu is trying to put the ecology of salamanders into focus and discover the things that are not known about them.

Kohmatsu is trying to develop a new analysis method for studying salamander feeding habits. His new method would include an analysis of the body's mucus in order to measure a stable isotope ratio of the carbon and nitrogen present in the mucus so as to identify the salamander's feeding habits. This stable isotope analysis is well known as a method for analyzing a food web. Previous studies have reported stable isotope analyses of fish mucus, but there is no precedence for the analyses of a salamander mucus.

The bio-elements in living bodies, such as carbon, nitrogen and hydrogen, are divided into stable isotopes that have different mass numbers. In the food chain, plants are eaten by small animals, which are then eaten by larger animals, which then again are eaten by even larger ones. At this point, the carbon and nitrogen of the eaten body are assimilated by the predator. Isotopes of a higher mass number are more likely to remain condensed in the body of predator. By measuring the ratio of stable isotopes whose concentration rates are fixed, it is possible to estimate the trophic level of the animal in the food chain and the origin of the food chain. "So to speak, it is in order to follow the traces of a material circulation in ecosystem," Kohmatsu comments. He also believes that radiocarbon used dating method provide important clues.

"When applying a stable isotope analysis to an unknown sample of salamander mucus, what must be clear at first is the discrimination factor for carbon and nitrogen," Kohmatsu says.
He is using the nine species of salamander endemic in Japan, which are reared by the Kyoto quarium, to calculate the discrimination factors.
This experiment begins with the breeding of crickets fed only rice bran. The crickets with a certain origin in the food chain will be fed to the salamanders. As the isotopes have assimilated substantially in their bodies, Kohmatsu collects the mucus to measure the ratio and derive the discrimination factors.

"When we are able to establish this methodology, I'd like to analyze the mucus of wild salamanders all over Japan in order to survey their feeding habits," Kohmatsu hopes.
"Furthermore, I would like to analyze the salamanders of the Great Smoky Mountains National Park in the east of the North America, which is considered the salamander capital of the world, and to compare them with those in Japan." Unlike Japan, where the 20 species live in a wide range from north to south, the National Park has a limited habitat containing about 30 species of salamander. "What will we learn if we compare different community of salamanders with a different species diversity and the environment? I'm excited about finding out."