The dad actually cares for the eggs, so that is really cool. Different males will also sneak in to participate in that process, but the den master is ultimately the top dog of that space. They each lay about 400 to 600 eggs, and the male fertilizes the eggs. Each den site has one big, dominant male who is considered the den master, but multiple females will come in and out to lay eggs. The breeding season starts in July and has been recorded going as late as November. What does their typical breeding season look like in the wild? Japanese giant salamanders are nocturnal, so they pretty much sleep all day. Our salamanders will also shack up in the dens and use them as a lounge spot. They are based off what our colleagues at Asa Zoo use. Our artificial dens are basically hollow PVC tubes that lead to upside-down flowerpots. In the wild, den sites would be rocks and caves. We also try to replicate their underwater den sites where breeding takes place and the eggs are laid and fertilized. Trying to do that artificially is very challenging, but hopefully we will find the right recipe. We are trying to trigger them with the same cues that they would have in the wild, without any interference from keepers. When it’s warmer and drier, we lower the water level. In seasons when there would be heavier rains in Japan, we raise the water level. We use a temperature cycling system and play with different water levels. Asa Zoo in Japan, where they have the most success breeding, has something called an “open system.” It uses water from the streams where the animals are naturally found. Honestly, it’s replicating the water that is found in their wild streams. Our females are 18.8-20.5 inches now and still growing. Females reach sexual maturity when they are about 23.5 inches long. Male Japanese giant salamanders grow faster than females, so our males are already sexually mature. That was last year, but the eggs didn’t develop. Honolulu Zoo was the first to get eggs in a North American zoo. Not yet, but we are always trying new things and think we are getting closer every year. ![]() ![]() Has the Zoo had success breeding Japanese giant salamanders? We also work quickly so they don’t get too agitated. They do have sharp teeth and can bite really hard, so we are very careful to stay away from the head. We use a net to get them out of the water and into the tub, weigh them and then gently ease them back into the water. We have a little tub that we put them in, and that goes on a scale. How do you weigh a Japanese giant salamander? We wouldn’t be surprised if these guys live to be 60 or 70. They are all about 20 years old, but Japanese giant salamanders have been recorded living over 50 years in human care. Orange Male lives on exhibit right now, while the others live in the breeding area behind the scenes. If they are all hanging out in the same den and he wants to be in that space, he will push his way in – even if the other salamanders are blocking the entrance. Hiro tends to be the most aggressive, so he is kind of the bully of the group. Orange Male tends to be the greediest and to beg for food the most. We refer to the other three by their physical characteristics: Orange Male, Full-tail Female and Notch-tail Female. He was named Hiro by the Japanese Ambassador to the U.S. They are already about 2 feet long, and our biggest male weighs about 6 kilograms (13 pounds). We have four Japanese giant salamanders at the Zoo – two females and two males – that were gifted to us from Asa Zoo in Japan in 2009. Video Tell us about the Japanese giant salamanders that live at Reptile Discovery Center. If they get caught in stagnant water, they will actually rock their bodies to get the water moving so that they can keep breathing. They also live in fast-moving streams, and moving water tends to have more dissolved oxygen than still water. These guys are very long and flat, and they have folds in their skin that create a lot of surface area for that respiration to occur. Oxygen goes in through their skin and carbon dioxide goes out – that’s how the respiration process works underwater. They can even lose limbs and recover just fine, even though their limbs won’t grow back. They can get beat up, but they heal like Wolverine. Males get a lot more aggressive and active during the breeding season and will fight with each other. People think of amphibians as delicate, but Japanese giant salamanders are very tough and resilient. They are very slow-moving though, so they don’t take off swimming a lot. We see that with the other salamanders in the cryptobranchid family, including the Chinese giant salamander and the hellbender. They have this big tail that is laterally compressed (flattened from side to side) that helps them move through the water. They can get up to 5 feet long and weigh 55 pounds. Japanese giant salamanders are the second-largest salamander species in the world. What makes Japanese giant salamanders unique?
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