Fiddler Crab Feeding Frenzy

In some places including Townsville, spring tides are enormous and neap tides are negligible. This creates a boom and bust cycle for animals at the top of the tidal range. If their area has been tidally flooded, then they will come out in a feeding frenzy. This post documents the wildlife I found on a salt pan near Townsville/Cape Cleveland following a big spring tide.

A long salt pan between parallel beach ridges

Beach ridges are long and grassy

The salt pans had million of fiddler crabs (Uca signata). Most were male and they were jousting and leaving the ground littered with ripped off nippers. Even in the distance there were clusters of male crabs. Perhaps they were fighting over a burrow. As the tide goes out, they firstly feed within the colony but when food (diatoms) runs out, they radiate out over the salt pan into areas that have few burrows into which to retreat when the are threatened. Some of the crabs even wanted to fight me! 

Crabs (Uca signata) were present in millions

Most of the crabs were male.

Swarms of crabs covered hundreds of metres. I did not think that a sunbaked salt pan was habitable at all, so it was a major surprise to see so much life. The salt pans belonged to a single species of crab. Other crab species were present within the fringing mangroves and especially within the more luxuriant grow near the creeks. There were large burrows beside the tiny rivulets that drained the salt pans but I could not find out what created those burrows. 

Big burrows near rivulets

Cape Cleveland in distance

Even in the above view, zooming in shows lots of crabs

The mud was sticky and formed ‘moon boots’ on my shoes. It is a change from the sandy mangrove substrates of Mackay or the organic muds of Cairns. The mud seemed to be mostly cracking clay. As the salt pans were long and narrow, one end was a marine environment and the other end was a fresh to brackish environment. The marine end had most of the crab and fish action. Almost no small animals were present on the now dry brackish end, save for some larger birds. These birds probably use the area to rest, as wide open spaces are safe spaces. Dingoes cannot sneak up on them.

Australian Jabiru

Brolga