The Hiroshima Hanzaki

By Rob Davis

I’ll admit it up front, I love amphibians! My foray into the world of professional ecology and conservation biology, was driven by a youthful passion to save the world’s declining frogs. It just so happened that I was an undergraduate student in the mid-1990’s when news was first breaking of the decline and extinction of amphibians world-wide. I remember reading articles about these declines, unprecedented in scale and was staggered by the fact that nobody knew why they were happening. The problem was so big that it threatened (and still threatens) the entire order of amphibians, and yet nobody I knew was working on frogs. I resolved that I would play my part and dedicate my studies to amphibians. I was lucky enough to undertake my PhD on frogs in south-western Australia and got to work on some  enigmatic and threatened frogs including the Sunset Frog, discovered in only 1994.


Sunset Frog Spicospina flammocaerulea (Pic: R.Davis)

Given my love of all things amphibian, I naturally have one on my wildlife bucket list. Topping this list, right there alongside tigers and polar bears, is the Japanese Giant Salamander Andrias japonicus. The Japanese affectionally bestow this species with the much easier name of Hanzaki. A member of the ancient family Cryptobranchidae, the Hanzaki has only two close relatives, the larger but much more threatened Chinese Giant Salamander (presumed extinct in the wild) and the near-threatened Hellbender of North America. Mysterious beasts, that have spawned many myths and legends, all members of this family are neotenic meaning that they retain juvenile features as adults, including gills and the ability to regenerate limbs.

I first heard about Japan’s surprisingly sizeable salamander on TV where I marvelled at pictures of the giant crocodile-like amphibian lurking in a remote mountain stream where it terrorised local fisherman and swimmers. I hoped then that one day I would be able to see this incredible creature in the wild. In 2014, I finally had the chance to make this dream a reality. When I was accepted to present at a conference in Tokyo, I carefully hatched a plan to add this amazing beast to my bucket list. My sleuthing tracked down a young researcher Yuki Taguchi in Hiroshima who kindly invited me to visit the captive breeding program that he runs at Asa Zoo. The zoo is a global pioneer and leader in breeding Hanzaki and breakthrough success in their captive program came through the use of enclosed tanks that simulate the holes in the river banks that Hanzaki excavate for breeding. Yuki’s studies have also highlighted the importance of understanding the social system of this species which lead him to give the dominant male (called the master) access to several females. This dramatically improved breeding success rates.


Yuki and the breeding tanks at Asa Zoo (Pic: R.Davis)

On my arrival at the zoo, I was very excited to see my first small Hanzaki inside the captive breeding tanks and to see a preserved specimen of the largest (documented) Hanzaki in the world, weighing in at 27.6 kg and measuring over 1.5 m!


The largest known Hanzaki specimen (Pic: Y. Taguchi)

The best news was yet to come, with the zoo extending me an invitation to join their monitoring program for wild Hanzaki in the Hiroshima countryside. Later that evening as Yuki and I drove through a verdant green landscape of rice paddies and lush native forest, he explained to me that most of the original streams in the region had been channelised and concreted for flood protection. This had created a big problem for Hanzaki as they could no longer burrow into the banks to breed. It also makes it harder for them to find cover and food. A further disruptive influence has been the construction of weirs to assist with flood regulation. This means that Hanzaki populations are now often isolated from one another especially as they are often unable to climb the large dam walls. Consequently, Hanzaki are often found with feet cut to pieces from trying to climb these concrete walls. One mitigation measure that Yuki and his team have undertaken is to install artificial breeding burrows at regular intervals in the concrete stream banks as well as alternative Hanzaki ladders to allow them to bypass large dams and move upstream. The Asa Zoo team also actively monitor population recruitment and move individuals if necessary.


A channelised and controlled Hanzaki stream near Hiroshima (Pic: R.Davis)

By the time we arrived at the first monitoring site, a small stream winding through open rice paddies and under a busy road, night had fallen and the air temperature had dropped. We met with two other vehicles and a small team of Hanzaki hunters emerged from the darkness, kitted up with head torches, nets and long poles for support in the fast-running mountain streams.


Asa Zoo Hanzaki hunter all ready to go! (Pic: R.Davis)

We headed off into the night along a short path through the rice field, and I quickly found myself on a riverbank. Clambering down the muddy, steep-sided bank, I took my first careful step into the icy cold, swift-running waters. It was quite an experience being chest-deep in water at night, carefully picking my way among uneven boulders, logs and other obstructions with my feet. My Japanese Hanzaki veteran and guide for the night was both faster and more agile than me, surging ahead and occasionally politely waiting for me to catch up, masking his wry amusement at my blundering progress. The main objective of our monitoring was to thoroughly search the stream as we travelled up it, using our head torches to try and spot Hanzaki below in the swirling waters. After perhaps an hour as my extremities were numbing from the cold and the gurgling water was soothing me into a sleepy stupor, I was beckoned excitedly by my assigned Hanzaki mentor (a lovely retired gentleman who has volunteered with surveys for the past 20 years). He pointed into a patch of water and said triumphantly “There, Hanzaki!”. Straining to make anything out in the swirling currents that refracted my light, I finally noticed that the large reddish log I was looking at was actually a Hanzaki!


Spot the Hanzaki (Pic: R.Davis)

I couldn’t believe the size of this magnificent animal, and how it managed to sit motionless so effortlessly in a current that was trying its best to sweep me off my feet. With an accomplished flick of his wrist, the Hanzaki wrangler placed his catch net in front of the ancient amphibian and ever so gently tickled its tail with his walking stick. The Hanzaki burst forward, but the Hanzaki master deftly twisted the net and hauled his prize catch to the shallower water near the bank. We readied all the measuring equipment and finally before my eyes, the wild Hanzaki of Hiroshima, my bucket list amphibian, emerged from he net for me to see of the first time. We measured it in a specially designed Hanzaki holding device (a PVC pipe cut in half!) before letting it go on it’s way. This one was about 80 cm.


The first captured Hanzaki ready for measuring (Pic: R.Davis).

I was thrilled with my first bucket list Hanzaki, but the night was young and to my great fortune I got to see and help measure a juvenile Hanzaki next. These are very rarely recorded and it is a sad reflection of the lack of recruitment in this population. No one knows for sure, but these denizens of the deep are thought to live for up to 100 years and are certainly known to live 30-50 years in captivity (the only verified record is 52 years). This doubtless means a slow generation time and combined with modern threats like changes to their stream habitat and introduced fish predators, there is concern that the viability of the Hanzaki population is declining. The IUCN accordingly lists Hanzaki as declining and estimates the population at 30-50 000 with an area of about 2000 sq. km of stream habitat occupied.


A juvenile Hanzaki (Pic: R.Davis)

As the night grew later and colder, we arrived at one final site, deep water at the base of a large dam wall, where Yuki had previously captured some larger adults. Although he told me that it was extremely rare to find many animals close to 1.5 m and that most are around 80 cm, he said we had a chance of seeing a Hanzaki over 1 m if we were lucky. After only ten minutes of surveying at this site, an excited call went up and we all rushed over to help one of the team net a larger animal. We readied the measuring equipment and as Yuki pulled the Hanzaki from the catch net, I gasped in excitement as the largest Hanzaki I was ever likely to see emerged from the water. This was the animal of legend that I had heard about; and it really did take two people to handle it!


A 1.2 m Hanzaki!! (Pic: R.Davis)

We measured this amazing animal and as we did, I couldn’t help but notice it’s tiny white eyes fixing me with an unblinking stare, and its incredible skin with gravel-like protrusions that helped it blend in perfectly with the rocky streambed. This gargantuan Hanzaki measured in at a little over 1.2m!


The eye of the Hanzaki! (Pic: R.Davis)

I was given the great honour of releasing this big old Hanzaki back into the water. As I gently placed it into the stream with the summer stars shining brightly above, it gently flicked it’s tail and disappeared into the dark swirling waters.


Rob living his bucket list dream, about to release a Hanzaki (Pic. Y. Taguchi).

I hoped that this wasn’t the last I would see of the Hanzaki and that it would be there for my young son and future generations to see. There is strong cause for optimism, with community support and village-based Adopt-a-Hanzaki schemes proving successful in raising awareness of this species. Hanzaki are protected by Japanese law and faring considerably better than their Chinese cousin which has been virtually exterminated from the wild for serving as a restaurant delicacy.  There is still much to be done, but the Japanese consider the Hanzaki a lucky charm and are engaged in its conservation. As I flew out of Hiroshima the next day, I gazed down at the streams running across the forested landscape and felt positive about the future of the Hanzaki and extremely lucky to have had an encounter with one of the world’s most amazing amphibians.