All is fair in love and war, but some animals take it to the extreme by temporarily turning themselves into something they're not. Findings published today in the journal Nature provide two new examples of how these mimics can get ahead.

The mating scene for giant Australian cuttlefish (Sepia apama) is rife with fighting and deception. Small males often scoop their much larger counterparts by pretending to be female themselves, which allows the runts to get closer to females of reproductive age. "In the blink of an eye they can pull out of it and go back to being a male," observes lead author Roger Hanlon of the Marine Biological Laboratory in Woods Hole, Mass. But although researchers had observed this behavior in the wild, it was unclear how successful the male mimics were at actually fertilizing females. Hanlon and his colleagues studied the creatures in their natural habitat and used DNA fingerprinting to analyze eggs and calculate the mimics' success rates. According to the report, the female impersonators fertilized female fish in 60 percent of their attempts, a success rate about twice that of honest male cuttlefish.

A second report by researchers at the University of East Anglia in Norwich, U.K., details a new example of mimicry in vertebrates, which usually lack the ability to switch appearances. Isabelle M. Cote and Karen L. Cheney found that the bluestriped fangblenny fish (Plagiotremus rhinorhynchos) is an exception and can turn its disguise on and off at will. By pretending to be a bluestreak cleaner fish (Labroides dimidiatus--an animal that helps other species by removing parasites--the fangblenny then ambushes its prey. Although the physiological basis of the animals' color changes is not yet understood, the scientists found that rapid shifts in hue are possible and that the fish can maintain the different appearance for several hours. This flexibility is beneficial because if there are no cleaner fish to impersonate, the fangblenny fish can revert to its signature blue stripe, which allows the creature to blend in better with the surroundings.