Kate on Conservation

The Mystery Of The Okapi’s Black Tongue

Closeup of an Okapi licking its face. Photo by Thorsten Spoerlein

I love to explore a good ‘strange fact’ when it comes to the animal kingdom. The okapi — often described as a cross between a zebra and a giraffe (with a short neck) — is one of those animals that could have easily featured in the lost of ‘10 Strange Animals You Probably Didn’t Know Existed‘. One of the okapi’s most unusual features is its black tongue. In this guest post, David Crespo shares his theory on why the okapi’s tongue is this unusual colour…

Why Do Okapis Have Black Tongues – Theory by David D Crespo

An okapi tongue, like a lot of things about this ‘unicorn of Africa’, is somewhat of an enigma. 120 years since its discovery by the Western world and we still can’t fully explain one of its most renowned features.  

What Colour is an Okapi’s Tongue?

An Okapi’s tongue is typically black, although it can look blackish-blue or blackish-purple under certain lighting. This is very similar to its closest living relative: the giraffe. Yet people have been thinking why these two animals, which live in completely different habitats, would share the same colour shades of the tongue. 

Close-up of an Okapi licking its face. Photo by Thorsten Spoerlein

What Causes the Okapi’s Tongue Colour? 

The reason for this strange tongue colour is a heightened amount of melanin (though in this case, it’s specifically eumelanin), which is a broad term for a group of skin pigments.     

What Does Melanin Do?

It’s these pigments that can create darker skin, irises and even hair. Although they have many functions, a major one is absorbing harmful Ultraviolet/UV radiation. This protects skin cells against cellular damage from constant and/or intense sunlight exposure. 

This protection extends to all forms of UV light including UVA, UVB and UVC, as well as blue light. Melanin is produced by a specialized kind of cell called melanocytes. These are mainly found in the outermost layer of the skin.    

Upon contact, any of those UV forms are swiftly and ruthlessly absorbed by the melanin before they can harm the sensitive nucleus and therefore DNA of the skin cells. It’s important they do; if the radiation reaches the nucleus, mutated cells could be ‘born’ during cell division or mitosis. This is how skin cancer spreads.      

Since giraffes are always out on the open savannahs, constantly exposing their tongues to the merciless African sun while feeding, the tongues have evolved higher quantities of melanin. Interestingly, the tone of both giraffe and okapi tongues is darker towards the tip than the back and on the topside compared to the underside. 

What’s the explanation for this arrangement of melanin? These parts of the tongue are most susceptible to UV radiation. 

Where Do Okapis Live?

Even though an okapi’s tongue is very similar to a giraffe’s, the two live in very different environments. Okapis dwell beneath heavily shaded canopies of tropical rainforests in the Democratic Republic of the Congo (DRC) in Central Africa. Specifically, they reside in the Central, Eastern and Northern of the country, mainly within the Ituri Rainforest and the Maiko National Park.       

Due to the dense, lush foliage of the emergency canopy and the understory layers, only about 1-5% of the daily sunlight normally reaches ground level. To the point where it actually takes longer to notice it’s daytime (or if it’s raining) when you’re on the forest floor than if you were in the upper layers! 

This means that ground-dwelling animals in the rainforest almost always live in a dimly-lit atmosphere with sunshine being a scarce sighting. But then why do okapis still have tongues crammed with melanin just like their giraffe cousins?

Why Does The Okapi Have A Black Tongue? (A Theory)

This may sound contradictory, but I believe okapis might have their blackened tongues for the same reason as their relatives – to prevent UV rays from damaging the skin cells of the epidermis. You might wonder how they can find such lighting with. The answer is light gaps (also known as tree-fall gaps).  

These large holes in the canopy are formed when one or several ‘emergent trees’ fall over, either because of old age, disease storms or parasites. These gaps allow light to shine through the canopy reaching down to the forest floor. And it just so happens the okapi’s feeding habits are perfectly suited to these light gaps.  

Okapi Feeding Habits

The falling of an emergent tree is a surprisingly common event in the rainforest and is usually the work of tropical thunderstorms. And without giant emergent trees hogging up all the space and sunlight, there are new opportunities for more sensitive, lower-growing plants to grow and flourish. 

For instance, whenever a light gap is formed and the patch of ground below is emptied, it is quickly colonized by several species. All of which are fast growers but aren’t adapted for a long lifespan.   

Expansive clearings are also where the vegetation will be less likely to have defensive adaptations. With all the extra space, sun, rain and nutrient-rich soil, those plant species can afford to put more time, energy and bodily resources to grow and regrow any parts eaten by hungry herbivores. 

Out of those herbivores, the okapi is probably the most prolific when it comes to feasting on understory flora. And the tongue is a major adaptation for the okapi’s feeding habits.  

Again like their giraffe cousins, okapis have tongues that are really long and prehensile. This means the tongues can actually wrap around and grab things, akin to a person’s hand. So okapis can use them to delicately pull pieces of foliage off branches and the ground.                 

They do this technique when feeding sparingly on the 100 or so plant species in their diet! Feeding only sparingly so to avoid ingesting too much of any one chemical or toxin that might be present in the plants devoured.

Along with the many short, rapid-growing and light-dependent plants found in the light-gaps, okapis sometimes enjoy eating charcoal, clay and bat droppings too. The reason behind these unusual cravings is because they contain the minerals and salts okapis require.

About the author

David Duarte Crespo is Portuguese wildlife author, who’s also currently studying a college course on Animal Management in the UK. In the past, he’s interacted with nature on multiple occasions: from being bitten by a Noble false widow as a toddler to keeping a Bearded dragon at 12 years old. His future plans involve going on to study for a Bachelor’s degree in biology/zoology and possibly a Master’s. He hopes to one day become a renowned and successful zoologist. 

Find out more at: https://www.facebook.com/david.crespo.56027/

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