[4] The species varies in colour from dark blue to brown or pale grey, and may grow to 15 centimetres (6 in) in carapace width and weigh over 500 grams (18 oz).

[2] In the United States it can be found in coastal areas of the Gulf of Mexico and Florida north to Vero Beach.

[3] Relatively cold water in the winter, less than 20 °C (68 °F), affects larval survival and restricts the species' possibility of spreading further north.

Experiments show that crabs can be drawn out of their burrows to investigate the sound of falling fruit, once out they initiate a search for food.

Crabs in the genus Cardisoma are able to detect small vibrations on the ground within the range of 10–1500 Hz and 70 dB.

When this occurs, C. guanhumi begins to gain weight, as more food is consumed and gathered for the first few weeks of the migratory period.

The crab will generally seal the exit to its burrow using mud, 6–10 days before it molts, to protect itself from predators.