male female ornamentation
Female animals look less attractive than male to avoid sexual harassment.Getty Images

Female animals generally look less colourful and attractive than their male companions to avoid sexual harassment, a study claims.

In some species, males have to compete for the attention of females, so having beautifully decorated plumage or other original traits are significant advantages. However, scientists are not entirely sure why females usually have less distinctive appearances.

By suggesting that female animals hide their sexual qualities because unwanted male attention may be detrimental to their fitness, the new research, published in Animal Behaviour, comes up with an original explanation to solve this mystery of animal biology.

Camouflage and increased fecundity

Previous studies show that males have to impress the females in order to get a partner, but that they too can also be quite selective. In fact, they may refuse to mate with a female if they are not satisfied of its body size, viewed an indicator of fertility.

Up to now, scientists had come up with two hypothesis as to why females didn't display more decorative features to avoid this rejection by male counterparts. The first one was that because females are the ones bearing the descendants or laying the eggs, they have a greater need for camouflage from predators.

Second, scientists found that ornamentation could affect fecundity. In this latest study the authors indeed explain that the "fitness cost of producing the ornamented trait would be high and females would do better to spend their limited resources on additional eggs".

The cost of harassment

Reviewing these different hypothesis, they realised that unattractive physical traits could also be interpreted as a protection against too much male attention.

"We suggest that if female ornaments signalled their sexual quality, females could suffer increased sexual harassment by males and this could be especially costly to fitness", says co-author David Hosken. Repeated sexual advances and harassment would lead to females losing energy and physical well-being.

Although this is still just another hypothesis, the scientists believe it is an interesting lead to follow-up on in future research. "We are not suggesting that male harassment of attractive females is the only explanation for lack of sexual ornamentation in females but want to alert researchers to the idea that this could be a contributing factor," comments Hosken.