Schütz and Taborsky (2005) directly observed and conducted experiments with cichlid fish (Lamprologus callipterus), a species in which the males are 12 times the size of females. Territorial males guard nests of empty snail shells. Schütz and Taborsky tested four hypotheses concerning sexual size dimorphism (SSD): 1) SSD results from intrasexual selection; 2) SSD results from intersexual selection; 3) SSD results from an ecological constraint on male body size; and 4) SSD results from an ecological constraint on female body size. They found strong support for