Chapter 36.6, Problem 2MC

Summary Introduction

To estimate:

The percentage of guarding males that successfully deterred mating attempts by disguised males with reference to the Figure 36.26 provided in the textbook.

Concept introduction:

Australian giant cuttlefish (Sepia apama) show sexual dimorphism. The males and females of the species greatly differ from each other in appearance. Females have shorter arms and dark patches on a white background. On the other hand, the males have longer arms and are whiter.

The species has a sex ration of four males to one female, leading to fierce competition among males for fathering the offspring. The largest males mate with the females and guard them after insemination. The males fight with other males that try to inseminate the females. This behavior accounts for larger male’s reproductive success.

The smaller males use another behavioral strategy called deception. They disguise themselves as a female by hiding the arms and changing skin color and try to mate with the females. Although most of the time they are deterred by the larger males, but sometimes they are successful to mate with the females.