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[Ingo Prangenberg]

I spent some time this weekend finding good sources of information regarding Birgus latro and was surprised to find that none mentioned if these Robber Crabs actually take food down into their burrows. These burrows can be as deep as 1 meter (not vertical, but diagonal) which would be lower than the 10 inches surveyed at the Seven Site.

Also, I cannot find the video with the pig experiment, where the strings were attached to the bones. I do not remember if any parts were taken down into burrows or left above ground, scattered in the near vicinity.

Since the burrows are intended mainly for daytime protection in order to prevent themselves from drying out, the chance of Coconut Crabs taking food scraps to lower layers of corral rubble may not be as high as I had hoped.

[Martin X. Moleski, SJ]

Also, I cannot find the video with the pig experiment, where the strings were attached to the bones. I do not remember if any parts were taken down into burrows or left above ground, scattered in the near vicinity.

Link to a small video in the article on "Taphonomy Experiments."

[Ingo Prangenberg]

Martin, thanks for the reading. It is funny that such an interesting creature has such an important part of its eating habits as an unknown.

The articles I found discuss this animal in detail. I was really hoping that the crab would take its food down into the burrow to feed. But the purpose of the burrow is one of protection from heat. It actually uses one claw to close/block the opening to the burrow in order to trap moisture inside, allowing its "lungs" to remain moist enough for them to work properly. That is not the claw they tend to use for feeding though.

One interesting clue that I would look for though is the mention of coconut burrow padding. Coconut crabs seem to take the coconut husk fibers with them into the den and create a sort of fiber pad. Even though mentioned in one article, I personally would doubt that this is for personal comfort, but rather to trap more moisture within the den/burrow. When deeper layers of any sites on Niku are excavated, finding matted coconut fiber pads would be a direct indicator of a previous crab habitation. These areas might be of special interest, especially is the vicinity to tree roots.

 

[Martin X. Moleski, SJ]

Martin, thanks for the reading. It is funny that such an interesting creature has such an important part of its eating habits as an unknown.

I guess a crab scholar would have to spend a lot of time watching them, day and night, to figure all that out.

Probably not a lot of money available to fund such studies!

The articles I found discuss this animal in detail.

If you think I should include any of those links in the wiki article on Birgus latro, you may drop them in this thread.  I haven't made a huge amount of progress on the flora and fauna categories. 

[Andrew M McKenna]

Ingo

Below are some photos of Coco Crabs in their burrows.  These were generally inside hollowed out tree stumps near the 7 site.  We did a bit of exploration in the crab burrows - remove crab, and while a crab wrangler entertained said crab, willing and brave subject crawled top half of torso into crab burrow - to see if there was anything interesting to be found in the burrow.  Nothing of interest was found, which would validate your finding that the burrow is really a cool place to rest, not a place to drag food or shiny things home to.

These burrows were not underground as we've heard about, and may not be exactly equivalent to what is the norm, but these crabs seemed happy, at least until I stuck my camera in their faces.

Andrew