Meeting Abstract
19.6 Monday, Jan. 4 Hood-building behavior by the fiddler crab Uca musica differs with sediment type and time exposed at low tide POPE, D. S.*; CHANG, K. H.; Mount Holyoke College, Massachusetts dspope@mtholyoke.edu
When animals build structures, it is not surprising that their building behavior might be affected by the construction materials available. Fiddler crabs are an excellent example of structure-builders; structures built of sand or mud next to or around individual burrows have been described in several fiddler crab species. Structures called hoods are built exclusively by males and increase their attractiveness to females, and can also serve as a guidepost for the male if he ventures too far from his burrow in pursuing potential mates. We studied the hood-building behavior of the fiddler crab Uca musica in Sonora, Mexico. At our field site, we found males of this species building hoods in two sites: on the sandy slope of the upper intertidal area of the shore, and on a lower sandbar, less than 1 km away, separated by a shallow channel from the shore. The two locations differ in two obvious ways: the sediment grain size on the sandbar is smaller and therefore holds more water than the larger-grained sandy sediment on the slope, and the males on the slope have a longer time of exposure at low tide. The slope is also exposed at every low tide, which is not true for the sandbar during low-amplitude (neap) tides. When comparing hood size, we found that the average height of hoods did not differ between sites, but the hoods on the slope were significantly wider and deeper; this difference may be due to sediment differences. Males on the sandbar started hood-building later in the day, and were less likely to rebuild their hoods if they were destroyed; these differences are likely due to the difference in exposure time between the sites. Males on the sandbar also built their hoods more quickly – this may be because the sediment was easier to handle, or because they had less time available.
