Size-assortative pairing in the fiddler crab Uca capricornis

A unique relationship exists between neighbouring males and females in the fiddler crab Uca capricornis. This experiment was designed to examine whether the nearest female or male neighbour was correlated with the size of a focal male. Throughout different experiments a total of 746 neighbour relations have been investigated. The size data collected during these experiments (531 male-female neighbours : 215 male-male neighbours) is the basis of this dataset.

Female size was found to be positively correlated with the size of her nearest male neighbour. Male size was also positively correlated with the size of his nearest male neighbour, but more weakly than between male-female pairs.