Rare Giant Salamanders Bred in Captivity

By Tim Hornyak

Imagine an amphibian up to 5 feet (1.5 meters) long that can weigh 80 pounds (36 kilograms) and snap chunks off your finger in a split second.

The Japanese giant salamander is one of the largest of its kind in the world: a mottled, slimy, living fossil that has changed little in millions of years.

giant salamander picture
A captive Japanese giant salamander at the San Antonio Zoo. Photograph by Joel Sartore, National Geographic

Being nocturnal and mostly aquatic, these super-salamanders are rarely seen. They lurk in cool streams in mountains and foothills. Though once caught for food, they’re now protected as a national treasure in Japan.

Hunting, pollution, and river damming brought their conservation status to “near threatened,” but now a nature center says it has made progress in breeding the giant salamanders. (Also see video: “Giant Salamanders Helped to Spawn.”)

“Although this is the second captive breeding in Japan, it’s the first in an indoor display tank,” said Akihiro Ito of the Hanzake Nature Museum of Mizuho in Shimane Prefecture. “It took us five years.”

Breeding Challenges

Hanzake, as the creatures are known locally, reproduce by external fertilization. A female lays hundreds of eggs that a male fertilizes after doing battle with other males. The male then guards the growing larval salamanders in his role as “den master.”

But giant salamanders often don’t thrive in captivity, so conditions had to be perfect. In consultation with the Hiroshima Asa Zoo, which has also managed to breed them, the nature museum used groundwater adjusted for acidity, and carefully controlled the temperature, light, and air in the salamanders’ environment. (Also see “Pictures: Seven Energy-Smart Zoos and Aquariums.”)

Staff placed two males and three females in the tank, which had a single den, but things didn’t go well at first. A male occupying the den would attack the others; in one case, a female was viciously mauled.

After several different combinations of males and females in the tank, finally a male called Daigoro and a female called Sachiko managed to mix it up, and a clutch of some 500 eggs was fertilized.

“Knowing how giant salamanders go about breeding and what conditions are necessary for that to happen comes in useful when considering how best to protect them in the wild,” said Tim Johnson, a Tokyo-based salamander enthusiast who has observed these creatures in the mountains.

“The way rivers have been modified in recent decades has made it difficult, and sometimes impossible, for them to migrate upstream to breed.”

Congrats to the new parents; we’ll keep track of how they do with their baby giant salamanders.

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