The nice thing about diving is that the ocean ecosystems I get to observe always show me something new. I have by now seen all the more common species off Sydney, but then, many of them display a range of behaviors which often surprise me and get me quite excited. Nudibranchs, octopi, wrasses, damsel fish, all of these act in interesting and surprising ways. Today a small species of horn shark did something I had not seen before.
Today, when diving with my buddy Big Al, we spotted a crested horn shark (Heterodontus galeatus) chewing on the egg casing of a Port Jackson Shark (Heterodontus portusjacksoni). No solidarity amongst the heterodontidae! The Port Jackson Sharks are much more abundant around Sydney during the colder months, and there are plenty of egg casings with nutritious embryos inside. The crested horn sharks have crushing plates, rather than the typical shark teeth, made for grinding crabs and clams. Still, it did not look easy to chew through the tough skin of the eggs, and we were watching the shark going at it for several minutes. It did not seem to be bothered by our presence. The whole episode was another fascinating piece of natural history, since it was so unexpected and we had ample time to observe the shark’s feeding efforts.