Rugs of Doom: wobbegong sharks eat big stuff.
Banded wobbegong eating an ornate wobbegong. Photo © Loren Mariani via iNaturalist.org.
I was randomly scrolling through the Elasmobranch Husbandry Manual the other day and came across this gem, on sharks in public aquaria:
“Many species, such as the wobbegong shark, have a tendency to eat almost any tank inhabitant that will fit in their mouths.”
Clearly, this required further investigation.
When we think about the ocean’s top predators, iconic animals like sperm whales, killer whales, and pretty good white sharks might spring to mind. Wobbegongs? Perhaps not.
Increasingly, though, I’m thinking they should. Wobbegongs don’t do much, but when they do… they go big.
Even other sharks, including smaller wobbegongs, can be an important component of their diet. My friend Charlie Huveneers found both Port Jackson sharks and ornate wobbegongs in the stomachs of larger wobbies in NSW, Australia, and calculated that wobbegongs fit into the food web at a similarly-high level to marine mammals.
About 50–80% of the wobbegongs he examined had empty stomachs; not surprising in an ambush predator. They’re champions at doing nothing. But when an unwary fish swims past… KAPOW.
Banded wobbegong eating yet another ornate wobbegong. Photo © Maarten De Brauwer via iNaturalist.org.
Aside from generally being grossinteresting, as so many of the best things in biology are, these observations do have some broader implications for Australian reefs.
Not much is known about wobbegongs, but there are high densities of these large predators at sites such as Julian Rocks off Byron Bay. I wouldn’t be surprised if their density compares to the 14–40 grey reef sharks per hectare documented at near-pristine French Polynesian atolls, which creates an ‘inverted trophic pyramid’ at that incredible site.
Could we be neglecting the ecological importance of these Rugs of Doom on subtropical and temperate reefs? It seems worth considering the question. I’m fairly obsessed with wobbegongs at the moment, so expect this to be an evolving topic…
In the meantime, got any other photos of wobbies eating big stuff? Link them below for my entertainment!
