Why Is Mammal Coloration So Dull?


It is easy to become mesmerized by the vast rainbow of colors on some tropical birds and reptiles. Mammals on the other hand have very dull colors in comparison. I wanted to find out why.

Mammals do not use color to attract mates, instead using other factors including size and strength. Very few mammals are poisonous and do not wish to attract attention. Mammals will use their dull coloration to camouflage themselves.

It seems that almost any color is a possibility, with striking blue frogs, vivid green lizards, and rich reds and purples in bird plumage. Some will even go a step further and change color. 

Yet, we don’t see this in the mammal world. In fact, we don’t see many colors at all. The color in the fur of most mammalian species tends to fall in tones of brown, black, tan, grey, white, and red. In this article we look at the reasons why? Are there any colorful mammals?

Why Are Animals Colorful? 

Typically, animals are colorful to attract a mate, warn off predators or send messages to each other. Male birds will develop breeding plumage in an astonishing array of colors to appear more attractive to mates in courtship rituals. Duller birds may rely on their nest building skills or song instead. 

Frogs and brightly-colored insects may use bright colors to show that they are poisonous and that predators shouldn’t even try and eat them. Then there are creatures like octopus and chameleons that can use color-changing cells to express emotion and information to others. 

Why Are Mammals Not Colorful? 

The simple answer here is that mammals don’t rely on the same tools in order to survive or attract a mate. Color isn’t a key part of attracting a mate for most mammals because there don’t use the same courtship displays as seen with birds. 

Other factors like size, strength, and the ability to provide also play a part. For many predators, it is simply a case of catching the scent of a female in heat and finding her. Mammals don’t always get to be as choosy as other animals. 

There are also very few venomous mammals, although there are shrews, loris, and platypus that can produce venom. This means that they don’t need the same warning colors. It doesn’t make sense for any mammal to advertise their whereabouts by using bright colors if they are not venomous.

As for communication, there are some mammals that will use color in a different way to signal to others in their group. Rabbits and deer species, for example, have white tails that stand out from the rest of their body. A flick of this white tuft is a signal to others that danger is lurking and they need to retreat. Mammals will also resort to vocalizations to communicate as a group, or to locate their mates or young. 

Do Mammals Have Reduced Sexual Dimorphism?

Sexual dimorphism is a term used when the male and female of the species appear to be very different. In some cases, you would be mistaken for thinking that they are different species. 

This happens a lot in the avian world when those males use color and display to attract their mate. A male bird of paradise will have a much more striking plumage than the more-drab brown female. We also see this with everything from birds of prey to ducks. 

However, sexual dimorphism is far less common in mammals. Males might be bigger and stronger. They may have horns or antlers for fighting. Otherwise they are pretty similar, especially in color. 

You would have trouble telling many males and females apart in a range of species without closer inspection. They don’t rely on this sort of aesthetic differentiation so there is no point wasting energy on changing their fur color when other traits will suffice. 

Do Mammals Use Color As Camouflage?

Brightly colored birds and reptiles aren’t so reliant on camouflage. Birds can fly away and Reptiles need their colorful patterns for other purposes. Mammals, on the other hand, do need to blend in with greater ease.

This is one of the reasons that you see so many natural tones like tans and browns in prey species. If you look at creatures like rodents, rabbit and hare species, deer, and antelope, you see very similar tones. They all need to blend in with their surroundings in case a predator comes along. If that doesn’t work, their agility and speed might allow them to out-run their hunter. 

But, it isn’t a whole lot different for predators either. Wolves have molted coats with browns and greys. Foxes have reds, oranges, and tan colors. Big cats can be a little brighter but lions and lynxes follow similar shades of brown, grey, and tan. That is because they can’t stand out either. They need to slink through the grass unseen and unheard until they are in a perfect position to strike. 

Another feature that you see on these coats is patternation. This includes stripes and spots to break up the shape of the animal and make them hard to see. That is why the brightly colored tiger disappears so easily in the grass. Prey species use similar patterns, particularly with banding on their legs, for the same purpose. 

You will often find that coloration of fur on mammals reflects the area in which they live. Desert animals can remain pale and sandy colored. Forest animals can get away with being darker. Then there are those like the Arctic hare and arctic fox that will change their coat in summer and winter. In winter, they blend into the snow with thick white coats. In summer, it becomes more molted and thinner as they blend into the tundra. 

Mammal fur doesn’t have the same properties as avian feathers or reptile scales. 

Another important factor here is that mammalian fur just doesn’t have the ability to produce that range of pigmentation. One thing that you will notice about the most attractive birds is the ability to create iridescent plumage. They can stand out with shiny blue and green tones that change in the light. Mammalian fur doesn’t do this, with the exception of the flattened fur of the golden mole. 

Are There Any Brightly Colored Mammals? 

There are some exceptions to the rule. One of the most colorful mammals is a primate called the mandrill. The male of the species has a striking array of colors on his face. This “mask” helps to solidify his dominance and attract females. In this respect, these apes do use color a lot more like birds than other mammals. 

Elsewhere in the primate world, The golden snub-nosed monkey has striking orange-toned fur and a blue face. Some species of langur will give birth to brightly colored babies so that they are visible when passed around the troupe. Also, there are the baboons with the bright-red backsides. None of these live in North America.

The important distinction here is that these creatures are all primates. Therefore, they have different physiology to their mammalian counterparts. One such difference is their eyesight. Primates, including humans, have much better color vision than other mammals. Others, such as dogs and cats don’t need to rely on this ability to see color. It is more important that they have better night vision if they are nocturnal hunters. 

Why Are There No Green Mammals? 

When animals do showcase color in their fur or skin, it tends to be on the blue end of the spectrum or into the oranges and reds. There are no mammals with green fur. You might ask why that would be the case when there are so many creatures that live up in the canopy of trees. 

First of all, it is much easier to camouflage yourself against a tree trunk or simply hide in a hole than to try and blend in with the leaves. Here the striped markings and neutral tones of tree-dwelling mammals make more sense. 

The creatures that try to blend in with leaves with bright green pigmentation are typically those that can rest on the leaves themselves. This includes frogs, lizards, and insects. 

However, there is one mammal that does things a little differently. The sloth is an incredible creature that spends the vast majority of its time up trees. They climb, eat, sleep, and will come down from the trees to defecate. These creatures may be big but they aren’t without their predators. A harpy eagle will take one if the opportunity arises. 

One way that these sloths blend into their environment is through the algae that grow on their fur. Some sloths can appear to be green in color as a result, but this has nothing to do with the pigmentation of their fur. 

Mammals Dont Need To Be Colorful

We can’t forget that it takes a lot of energy to shed coats and plumage to create something more practical. Birds can get away with this because they know that they will have a better chance of breeding as a result. There is a pay-off for the effort. 

For mammals, it makes more sense to retain a dull coat to blend in with the crowd, and the surroundings, and simply survive. Evolution will always produce exceptions to the rule but, for most mammals, a lack of color is the best approach. 

Sources

https://blog.wcs.org/photo/2016/02/08/a-monkey-that-changes-color-lunar-new-year-bronx-zoo/

https://www.newscientist.com/article/dn21390-worlds-only-iridescent-mammal-is-a-shiny-accident/

https://academic.oup.com/bioscience/article/55/2/125/221478

https://jeb.biologists.org/content/207/12/2157#:~:text=leucophaeus%20have%20the%20most%20complex,rump%2C%20perineal%20and%20genital%20areas.

Bryan Harding

Bryan has spent his whole life around animals. While loving all animals, Bryan is especially fond of mammals and has studied and worked with them around the world. Not only does Bryan share his knowledge and experience with our readers, but he also serves as owner, editor, and publisher of North American Mammals.

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