Why Are Hellbenders Eating Their Own Eggs?

Hellbenders have a scary-sounding name and a very odd appearance. These elusive stream dwellers, which can grow over two feet in length as North America’s largest salamander species, have earned nicknames such as “snot otter” and “lasagna lizard” because of their slimy, wrinkled bodies. But their looks aren’t the only unusual thing about them.

Unlike most other salamanders, which tend to lay eggs and go, hellbenders are known for caring for their young. After mating with a female and digging out a safe den in a streambed for her to deposit her eggs, male hellbenders stick around and guard them until they hatch 5-6 months later, chasing away predators, fighting other males, and checking on the eggs periodically. All in all, these salamanders make excellent dads… except for when they decide to eat the eggs they’re supposed to be guarding.

This behavior, known as “filial cannibalism,” has been observed many times in hellbenders, baffling researchers. Why eat the eggs you’ve spent so much time and energy producing? One theory is that the hellbenders are just eating eggs that were fertilized by a different male, taking out the competition by ensuring their own eggs don’t have to fight as much for resources after hatching. But it’s not clear how the salamanders would know which eggs are theirs and which belong to other males. Plus, one 2017 study compared the DNA of a male hellbender with eggs he had eaten and found he was indeed the father of his meal, confirming these salamanders are really eating their own children.

Another idea is that the hellbenders need to eat some of their eggs to avoid starving while guarding the dens for so long. A study done in 2020 used cameras to track the activity of male hellbenders guarding dens and found that they spent less than 3% of their time away from their eggs, which doesn’t give them a lot of time to eat. If this is the case, they may try to lessen the damage they cause by eating the worst-off eggs. A closely related species of salamander, the Japanese giant salamander, has been found to selectively eat dead or underdeveloped eggs from their own dens, which also protects the healthier eggs from disease; it’s quite possible the hellbender is doing something similar. So don’t judge these salamanders too harshly for their odd behavior -- it might just be their way of showing fatherly love.