Hanlon, R. T., Naud, M. J., Shaw, P. W. & Havenhand, J. N. 2005 Behavioural Ecology: Transient sexual mimicry leads to fertilization. Nature 433, 212.

Male Sepia apama, commonly called the giant Australian cuttlefish, have adopted a technique to sneak copulations with females who are being guarded by larger males. By changing their appearance to resemble a female, smaller male cuttlefish can fool larger males into thinking they are female. However, does this technique actually give an advantage to sneak copulators?

When giant Australian cuttlefish breed, they come together to form large breeding groups, where on average of four males mate with a single female. Additionally, female giant Australian cuttlefish are picky and only mate with 30% of males that try to copulate with them. Because there is so much competition between males, females are typically guarded by large males constantly. Larger males who constantly guard females usually receive 64% of the copulations.

Hanlon et al. recorded mating interactions while on SCUBA. They discovered that female-mimicking males would alter their appearance by changing their skin pattern and by mimicking the egg-laying behaviour of females, all while concealing their fourth arms (male cuttlefish have bigger and whiter fourth arms than females). The team found that female-mimicking males were able to trick the guarding males and get close to the female 30 times in 62 instances. Furthermore, 2 out of 3 sexual encounters of female mimics led to fertilization.

Male cuttlefish are able to effectively trick larger males by altering their appearance to look like females. Furthermore, the results demonstrate that female mimics were able to mate with guarded females.

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(posted Jan. 4, 2016)