Crabs in the sand

This past Memorial weekend, my wife and I remembered, and are thankful for all of the men and women that have given the ultimate sacrifice for our country. We also thank all the current men and women in the military for their service.

As do millions of other Americans, we also celebrated the unofficial first day of summer by traveling to Galveston for a beach day.  It was a hot and sunny day that was a welcomed contrast from all the extreme storms and flooding that has been occurring in southeast Texas.  We walked onto the beach and set up our chair and beach towel close to the sea wall behind a row of chairs and umbrellas that you need to pay for. We apparently picked a wonderful spot, because soon after I sat down, I noticed multiple holes in the sand that I immediately identified as burrows! I was sitting in the chair reading a book while I unknowingly was becoming sunburnt, when my wife said: "look, there is a crab coming out of the hole."  I immediately looked, however, the fast crab quickly jumped back into the burrow. My wife took our camera and waited patiently until she took a picture of the crab that came out of the burrow.

A crab on a sandy beach that is half way in their burrow.

Based on some basic Googling, this type of crab is commonly called a sand crab. In particular, this crab I believe belongs to the family Ocypodidae, a type of semiterrestrial crab that includes the ghost crab and the fiddler crab. Based on viewing images, it appears that this is likely a ghost crab because the male fiddler crab contains a large claw, which I did not see in any of these crabs. If based on the pictures I am mistaken about the identity of these crabs, please let me know and I will change my identification.

A smaller ghost crab in their burrow. The crabs color very closely matches the color of the sand, presumably to avoid predators. 

I wish I had a shovel at the beach because I would have loved to have excavated the burrow to see how deep the burrow went as well as the shape. When I did a Google search for ghost crab burrows I found a couple websites about these crabs. To summarize, ghost crabs belong to the genus Ocypoda. They can be located all around the world on sandy beaches in tropical and sub-tropical coasts. The ghost crab dig burrows to keep cool during the daytime. The burrows typically enter the substrate at a 45-degree angle and can reach a depth of to 4 ft according to the one website (which I will list below). Adult crabs typically have two entrance shafts. Interesting facts I read include that males tend to neatly pile the excavated sand next to the entrance, while females tend to scatter the sand all over. I am not sure what is considered "neat," so I am not sure if I would call the crabs in the above images female or male. Another interesting fact is that younger crabs tend to dig burrows closer to the water whereas older crabs tend to have burrows further away from the water.

While I was sitting at the beach looking at the crabs and their burrows, I did notice that there were balls of sand by the entrance of the burrows. As I continued to watch I saw a crab appear, and throw one of these balls away. I think I was watching a crab currently excavate a burrow. I started to notice that all the crabs were appearing and throwing these balls of sand away from the entrance! Just an interesting note, I also noticed that these balls of sand were wet, indicating that the crab had likely reached the water underneath the sand. Below I will show a video that my wife took of the crab throwing the ball of sand that it excavated.

Here are the websites I looked at for information regarding the ghost crab

https://en.wikipedia.org/wiki/Ghost_crab
http://www.animalspot.net/ghost-crab-sand-crab.html