Mammalian fur performs vital functions for survival, acting as thermal insulation to prevent heat loss. Furthermore, it serves as physical protection against damage, parasites, and solar radiation, and in certain aquatic species, it aids in water repellency. Additionally, fur plays a crucial role in camouflage, both for hunters and their prey.
However, no mammal has green fur. A 2013 investigation analyzed the 29 existing orders of mammals and observed that the vast majority have fur in shades of gray or brown. These colors are generated by the combination of two types of melanin: eumelanin, associated with black and brown tones, and pheomelanin, responsible for yellowish, orange, and reddish tones.
The reason for this predominance of colors lies in the fact that they are the most advantageous for camouflage, thus being favored during the evolutionary process of the species. Although the factors defining the colors are more complex than just the presence of melanin, it is now known that there are two main mechanisms involved: pigmentation regulation, which modifies the type, density, and distribution of pigments in each hair, and pigmentation standardization, which creates specific patterns, such as the spots of a jaguar. The animal's age and climatic season can also influence coat coloration.
Even considering all these aspects, mammals do not possess a known mechanism to produce green fur through pigmentation. The only apparent exceptions are the six known species of sloths, whose greenish appearance is due to the presence of algal communities covering their fur. Scientists speculate about a possible mutual benefit relationship: the algae gain shelter and access to sunlight on the sloth's fur, while these arboreal mammals gain green camouflage against predators.
The question then arises as to why evolution did not select for green fur if such camouflage were beneficial to some animals. The answer may be related to vision. Trichromatic animals have three types of functional cones in the retina, allowing them to perceive a wide variety of colors. In contrast, dichromats have only two types of functional cones, which restricts their ability to differentiate certain colors. Most mammals are classified as dichromats, although humans are trichromats.
This visual difference helps clarify the previous question. To a human, a tiger might appear orange due to our trichromatic vision. However, to dichromat animals, such as pigs or deer, it might appear green—a color that favors the camouflage of these animals. Thus, evolution did not need to develop green tigers because the prey that sees the tiger in the same way, regardless of whether it is green or orange, reduces the relevance of the distinction between these two colors.
This topic was investigated by a team of scientists from the University of Bristol in 2019. The study concluded that 'producing green fur would require a significant change in mammalian biochemistry,' which represents a considerable effort for minimal evolutionary gain. The researchers also pointed out that, for species that rely on camouflage against dichromats, there is 'little evolutionary pressure for them to actually become green.' On the other hand, for species that need to camouflage against trichromats, other fur characteristics, such as patterns and contrasts, may be more important than simply changing the color.
The peacock is considered one of the most beautiful birds in the world, and in India it holds the status of a national symbol. However, there is often confusion regarding the total number of peacock species worldwide, as well as whether white, blue, and green peacocks are different species.
According to BirdLife International data, there are only three living species of peacocks in the world. White or other colored peacocks are not considered separate species.
BirdLife International, which is the official organization for the IUCN Red List of Birds, states that there are three species of peacocks in the world: the Indian Peafowl, the Green Peafowl, and the Congo Peafowl. These species are found in different parts of the world and differ in appearance, habitat, and conservation status.
Although the peacock's appearance is determined by its magnificent feathers, scientists do not define a bird species solely by color. They also consider body structure, genes, and natural habitat. This is why the white peacock, despite its external difference, is not recognized as a separate species.
The scientific name for the Indian Peafowl is Pavo cristatus. It is the national symbol of India but is also found in some regions of Sri Lanka, Nepal, and Pakistan. Later, it was introduced to many countries in America, Australia, New Zealand, and Europe. According to the IUCN Red List, this species is currently not endangered.
The scientific name for the Green Peafowl is Pavo muticus. It inhabits Myanmar, Thailand, Cambodia, Laos, Vietnam, southern China, and the island of Java in Indonesia. BirdLife International notes that the population of this species is declining due to the reduction of forest areas and hunting. For this reason, it is classified in the IUCN Red List as an endangered species.
The scientific name for the Congo Peafowl is Afropavo congensis. It is the only species of peacock found in Africa. Its natural habitat is the dense forests of the Democratic Republic of Congo. It is smaller than the Indian Peafowl, and its feathers are not as bright.
This issue causes the most misunderstanding. According to the San Diego Zoo Wildlife Alliance and the Smithsonian National Zoo, the white peacock is not a separate species. It is a rare color variant (Leucistic Variant) of the Indian Peafowl, whose feathers turn white due to genetic changes. Therefore, scientists still believe that there are only three living species of peacocks in the world.
