Prowling headfirst into rushing underwater currents, a Japanese Giant Salamander moves methodically across the stony streambed. The Sun has set on northern Kyushu - the southernmost major Japanese island - and the water in this mountainous stream flows fast and cold. While most animals return to comfortably warm shelters to sleep through the night, Andrias japonicus comes alive in this chilly darkness. The cooler temperatures create an ideal environment for the enormous amphibian, and considering its miniscule eyes and feeble vision, the absence of light is of no consequence. Relying on a line of sensory nodes extending the length of its body, the nocturnal beast navigates the terrain by feel, detecting the slightest vibrations in the water in the same way humans employ tiny hair cells in the inner ear to sense sound.
When an unsuspecting fish swims nearby, the otherwise sluggish predator displays a burst of unexpected speed, lashing its broad, flat head to the side. Camouflage is paramount to hunting, and the Japanese Giant Salamander seamlessly blends into the surrounding streambed; without light, the fish never saw its assailant's dark brown and black - marbled skin with dusky blotches - against the backdrop of similarly colored stones. Once captured, the fish has no hopes of escaping. By generating a negative pressure inside its warty mouth, the Japanese Giant Salamander creates a strong suction to catch its prey. The fish can only flail in vain before being sucked into the salamander's stomach.
Death is inflicted within seconds, but digestion will take substantially longer. Japanese Giant Salamanders have slow metabolisms, and can live satiated for several days or weeks before hunting for another meal. Despite this infrequent eating schedule, the world's second-largest species of salamander measures a massive 1 to 1.5 meters (3-5 feet) long and weighs an average of 25 to 30 kilograms (55-60 pounds). Only the Giant Chinese Salamander, a close and critically endangered relative, is larger.
Unlike its larger cousin across the East China Sea, the Japanese Giant Salamander remains safe from the Endangered Species List for the time being - but an array of factors may put it there in the near future. Increasing water pollution presents has proven particularly problematic since adult salamanders take in oxygen from the surrounding water through their skin. Deforestation further threatens the species, as soil erosion and silt disrupt ideal aquatic conditions and eliminate other potentially livable habitats. While these examples of human destruction have inadvertently caused a dangerous decline in the number of Japanese Giant Salamanders, man has also intentionally targeted these animals for centuries to use in cooking and traditional medicine.
Dispersed between restricted regions on the Japanese islands of Kyushu, Honshu, and Shikoku, colonies remain isolated from each other with no natural means of joining together. If numbers continue to decline within each of these groups, humans will need to intervene again, this time as conservationists who will need to facilitate rebreeding programs by combining individuals from various territories. In the meantime, the species must rely on themselves to reproduce in sustainable numbers.
Breeding season occurs every August, as hundreds of Japanese Giant Salamanders converge upon river regions abundant in rocky caverns and burrows. Between males, the fight to stake claim to prime territory for nesting sites can escalate to deadly proportions. Confrontations are commonplace and brutally physical. The winners welcome females into their breeding pits to commence egg laying and fertilization. The losers lucky enough to survive suffer severe bodily injuries; the rest wash up on the riverbanks as carcasses.
Back below the water's surface, females lay anywhere between 400 and 500 eggs - strung together like a thread of beads - in a pit while the male follows behind providing fertilization. Once the visiting female departs, the male remains to guard the pit from predators until the eggs hatch twelve to fifteen weeks later.
Upon hatching, tiny larvae emerge measuring no more than 3 centimeters (1 inch) long. Unlike their fully matured parents, these larvae begin life with gills and breathe dissolved oxygen in water. While they will ultimately grow into impressive beasts, the larvae undergo a slow growth process in the early years; at the end of the first year, they will only have grown to 10 centimeters (just over 3 inches) and after three years they still measure a mere 20 centimeters (just under 8 inches). For those individuals who defy the high early mortality rates and reach this length, however, the process of metamorphosis finally begins, as gills disappear.
As adults, Japanese Giant Salamanders command the food chain from the top, spending evenings devouring fish, crayfish, snails, insects, worms, and frogs - that is, whenever they are even hungry enough to eat. Daytimes are spent dormant, hidden beneath riverbed rocks. Outside of breeding season, this daily cycle remains constant until death, which does not come soon for these large amphibians. While the average lifespan of the Japanese Giant Salamander likely exceeds 40 years, anecdotal evidence has shown specimens that can live for nearly a century.
A Japanese Giant Salamander is about to capture another mountain stream inhabitant: a Japanese trout of the Salvelinus leucomaenis complex. There is some technical confusion over the races, varieties, and subspecies of these fish, though the example depicted would most likely be called "Yamato Iwana" (Salvelinus leucomaenis f. japonicus) from the Island of Honshu.
Giant Japanese Pepper Fish
1-1.5 meters (3-5 feet)
25-30 kilograms (55-60 pounds)
40-60 years in the wild
Cold mountain rivers and streams
The Japanese islands of Kyushu, Honshu, and Shikoku
Insects, crayfish, snails, fish, worms, frogs
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In the wild, infections caused by chytrids commonly afflict Japanese Giant Salamanders.
Once he has won a nesting pit, the male will often retain it in future breeding seasons.
When threatened, the Japanese Giant Salamander will excrete an odorous milky substance, which smells like Japanese pepper. As a result, the Japanese sometimes refer to this species as the Giant Japanese Pepper Fish.
Japanese Giant Salamanders often serve as hosts to a variety of parasites, including roundworms.
The Japanese Giant Salamander does not need saliva to swallow its food, needing only a combination of water and suction to suck in its prey.