​From finches to chameleons: The surprising reason why male animals are more colourful than females

The natural world has numerous animals, be it birds that grace the sky, fishes that trifle through water, or animals that walk and race on land. But have you ever noticed that the males of most of these creatures are more colourful than the females? Well, though bizarre, it is true. In the natural world, male animals often stand out with their dazzling colours and unique patterns, capturing attention wherever they go. From the bright feathers of peacocks to the vibrant scales of tropical fish, these vivid displays are more than just beautiful, they play a crucial role in the animal kingdom.

Animals like the male house finch, red-winged blackbird, mandrill, and Jackson’s chameleon all use their bright colours to tell important biological stories. But why is it that males tend to be more colourful than females? The answer lies mainly in sexual selection, a concept introduced by Charles Darwin to explain traits that give an individual an advantage in reproduction, distinct from natural selection which focuses on survival advantages. Male animals often develop bright colours and striking physical features to outcompete other males and attract females.

Here are some reasons why most male animals are more colourful than the femalesDisclaimer: This article is based on widely accepted scientific theories, including Charles Darwin’s work on natural and sexual selection. These concepts are presented in a simplified manner for easier understanding, and variations may occur across different species.

Sexual selection favours males with traits that improve their chances of mating, like bright colours, because females choose mates based on attractiveness. This selective pressure makes males develop beautifully coloured plumage, fur, or fins which are absent or less pronounced in females, for example in peacocks. These colours help males stand out and point towards genetic fitness and good health. Brightness or particular patterns act as advertisements to females, indicating that a male can successfully survive despite the risk of being more visible to predators.

Males also use their bright colours to compete with other males, establishing dominance over rivals. The vivid colours demonstrate strength and fitness, helping avoid physical fights. For example, male chameleons display bright hues to show dominance, while losing males fade to dull colours. Such visual signals maintain social hierarchies and reduce the need for risky confrontations, ensuring the fittest males secure access to females.

Bright colours indicate a male’s health since producing and maintaining vibrant pigments requires good nutrition and a strong immune system. In species where colours are derived from diet, such as finches, brighter males often control better territories with more food resources. This signals to females that mating with such males will offer better survival chances for their offspring in a rich environment.

In some species, like the shorebird phalarope, females are the more colourful ones and compete for males. This role reversal reflects different reproductive strategies where males invest more heavily in offspring, leading females to attract mates more actively. These exceptions show how sexual selection shapes colour based on species-specific mating systems and parental roles.

Colours are also a mode of non-verbal communication during courtship and conflicts. For example, red shoulder patches on male red-winged blackbirds intimidate rivals and attract females. Mandrills’ bright red noses are a sign of dominance and vitality. Such vivid displays influence mating success and territorial control, playing a pivotal role in reproductive strategies.