Seeking a role model for fatherhood? Look no further than an enormous, secretive salamander who only sometimes eats his babies.
You’re not likely to stumble across a Japanese giant salamander in the wild, and if you did you might wish you hadn’t. These oversized amphibians are the golems of the animal world: bloated and tiny-eyed, they lurk in stream banks like animated sacks of mud. Andrias japonicus can grow almost 5 feet long, making it smaller than its Chinese cousin but larger than the related North American hellbender (a.k.a. “snot otter”). Japanese giant salamanders are rare and shy, though, so you won’t see one unless you go searching.
Scientists in Japan spied on two of the elusive animals to follow up on earlier hints that the blobby creatures might be great parents. Not the moms, that is—they skip out after leaving their eggs—but the dads.
Only some male salamanders are lucky enough to have nests. These big guys who secure a stream-bank burrow are dubbed “den masters,” as if they were getting ready to preside over a troop of Boy Scouts instead of several hundred gelatinous eggs. Females enter the burrow to mate, and some roving smaller males sneak in to join the action. But afterward, they all leave the den master alone with his charges.
The researchers placed videocameras where they could observe the nests of two male giant salamanders in Japan. One was an artificial nest humans had built for the animals (the species is federally protected). The other nest was naturally occurring. The cameras captured the den masters’ behavior from egg-laying in the fall through when the young larvae left home the following spring.
In a surprise twist, the den master of the artificial nest had abandoned it by early December. This was unfortunate for his young. But it let the scientists learn what happens to salamander eggs without a dad’s care.
The video footage revealed that both dads actively took care of their young (at least until one became a deadbeat). They both fanned the water around the eggs with their tails, probably to ensure the embryos got enough oxygen. The dad in the natural nest, as his eggs grew and hatched, did other things to take care of them: He periodically thrashed his head or body to stir up the eggs, which helps them develop normally. He slowly scanned the eggs and the hatched larvae to check on them. And once, he ate a larva.
The scientists say this last behavior, called “hygienic filial cannibalism,” is another mark of a good father. The baby he gulped down was already dead. By weeding out dead or dying young, a salamander can keep dangerous mold from spreading through the nest. (At one point this dad also slurped up a live larva, but he spit it back out. Mistakes happen.)
How well did the fathers do at keeping their babies alive? That cannibalized baby salamander was the only death scientists observed in its nest. But over in the abandoned nest, things went much worse. The researchers found over 100 dead larvae in that nest. They also counted 30 predators visiting the abandoned nest, including minnows and leeches. Meanwhile, the nest guarded by its dad had no predators.
From egg-laying to empty nest, the commitment of a giant salamander dad can last seven months or longer. But having their father around seems to help young salamanders survive. When they grow up, some of them will become good parents too—cannibalism included.
Image: Smithsonian’s National Zoo (via Flickr)