Sand Bubbler Crab Pellets at Cape Tribulation

Small ball-shaped sand pellets produced by the feeding activities of the "Sand Bubbler" Crab

On many sandy beaches along the Queensland coast of eastern Australia there are millions of small sandy balls. Each one is just a few millimetres across. They can form extensive mats or patterns as they cover the shore at low tide. There were many decorating the sand at Cape Tribulation when I visited in 2011. Closer inspection reveals small holes in the sand, usually at the centre of radiating lines of balls. These balls are the result of the feeding activities of small sandy coloured crabs that are themselves rarely seen. The holes are their burrows. They are the “Sand Bubbler” crabs belonging to the genus Scopimera, often S. inflata. The balls are created as the crab feeds on the organic matter attached to the sand grains on the surface around its burrow, and rolls up the cleaned grains into balls before moving on to the next spot.

The patterns vary according to the moisture level of the sand and its organic content, as well as the species concerned, I would imagine. I’ll post some more pictures later showing an interesting variation on the sand ball patterns from the other end of Cape Tribulation beach.

11 thoughts on “Sand Bubbler Crab Pellets at Cape Tribulation

  1. Fascinating, Jessica! I’ve seen little pellets around the holes of small fiddler crabs in Sarasota, Florida, but always assumed they were made in excavating the underground sanctuaries. Sarasota’s fiddlers don’t arrange the pellets so artistically, though.

  2. Thank you, Linda. What intrigues me most about these pellets is the speed with which they are made. All the pellets that you see are produced in the few hours between the tides, and presumably the crab cannot work on the surface in the hottest part of the day. Everything is washed away each time the tide comes in and a fresh sandy canvass is produced on which the crabs can work.

  3. I photographed these at Cape Tribulation, but did not know what they were. I had never seen them before. Would it be ok if I put in a link to your post when I post my photo? Your post is educational.

  4. I also saw many wonderful things in Australia that I had never seen before. I was lucky enough to find a couple of books on the wildlife of the coastal and rainforest habitats in Queensland but I have still had to look up a lot of things back home. Have you seen my earlier posts on Queensland topics?

    I would be delighted if you linked your post to mine.

  5. Hi Jessica! I just posted my Sand Bubbler photos and put in the link to your blog. I have seen quite a few of your Queensland posts. I especially recall the rocks and abstract patterns from Queensland. I gave those a revisit! Your blogger friend, Pam K.

  6. Thank you for letting me know, Pam. Your pictures are brilliant. The designs left by the individual crabs are very attractive and provoke the imagination. Glad you liked my rock photos. I realised this week that, although I have posted I think 66 articles about the nature I saw on my trip to Queensland, I still have a lot more to write about using the 8,000 shots I took back in 2011.

  7. Thank you, Jessica. I enjoyed learning about the crab and doing the post. We only returned from Australia four months ago and I have been working steadily on photos since then. It will take me some time! We started in the east and traveled to the Northern Territory and then west.

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