Individuals of the spider crabMithrax spinosissimusliving in a canal in the Florida Keys were marked and their movements followed over a four‐month period. Individual home range size, extent of daily movement, and extent of day‐night movement were calculated. Although males and females moved similar distances when they did move from one crevice to another, males re‐located more frequently. There was no correlation between animal size and any measure of movement. Extent of daily movement was inversely correlated with spider crab density, especially for female crabs.