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 but other factors, including size and strength. Very few mammals are poisonous and do not want to attract predators’ attention. Mammals will use their dull coloration to camouflage themselves.
Almost any color is possible, 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 of most mammalian fur tends to fall in brown, black, tan, grey, white, and red tones. In this article, we look at the reasons why? Are there any colorful mammals?
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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 to eat them. Then there are creatures like octopuses and chameleons that can use color-changing cells to express emotion and information to others.
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Why Are Mammals Not Colorful?
The simple answer is that mammals don’t rely on the same tools to survive or attract a mate. Color isn’t a crucial 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. It is simply a case of catching the scent of a female in heat and finding her for many predators. Mammals don’t always get to be as picky as other animals.
There are also very few venomous mammals; shrews, loris, and platypus 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 using bright colors if they are not venomous.
As for communication, some mammals will use color differently 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 signals 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 species appear to be very different. Sometimes, you would be mistaken for thinking they are other species.
This often happens 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.
Without closer inspection, you would have trouble telling many males and females apart in a range of species. They don’t rely on aesthetic differentiation, so there is no point wasting energy 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 why you see so many natural tones like tans and browns in prey species. You see very similar tones if you look at creatures like rodents, rabbit and hare species, deer, and antelope. They must blend in with their surroundings if a predator comes along. Their agility and speed might allow them to outrun their hunter if that doesn’t work.
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.
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Another feature that you see on these coats is patternation. This includes stripes and spots to break up the animal’s shape and make them hard to see. That is why the brightly colored tiger disappears so quickly 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 integrate into the tundra.
Mammal fur doesn’t have the same properties as avian feathers or reptile scales.
Another critical factor is that mammalian fur can’t 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, except for the flattened hair of the golden mole.
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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 use color 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 langur species will give birth to brightly colored babies so that they are visible when passed around the troupe. Also, there are the baboons with bright-red backsides. None of these live in North America.
The critical distinction here is that these creatures are all primates. Therefore, they have different physiology from 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.
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Why Are There No Green Mammals?
When animals 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 so many creatures live up in the canopy of trees.
First, it is much easier to camouflage yourself against a tree trunk or hide in a hole than to try blending 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 can typically 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 most of its time up trees. They climb, eat, sleep, and will come down from the trees to defecate. These creatures may be giants, 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 green in color, but this has nothing to do with their fur’s pigmentation.
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Mammals Don’t 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 they can breed better. There is a pay-off for the effort.
It makes more sense for mammals to retain a dull coat to blend in with the crowd and the surroundings and survive. Evolution will always produce exceptions to the rule, but a lack of color is the best approach for most mammals.
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Sources
American Institute of Biological Sciences
Journal of Experimental Biology
Bryan Harding is a member of the American Society of Mammalogists and a member of the American Birding Association. Bryan is especially fond of mammals and has studied and worked with them around the world. Bryan serves as owner, writer, and publisher of North American Nature.