Hippos are large, mostly herbivorous mammals that inhabit rivers, lakes, and swamps in sub-Saharan Africa. They are well known for their massive size, aggressive territoriality, and amphibious lifestyle. But do hippos also change color as they age or depending on their environment? In this article, we’ll explore what gives hippos their distinctive coloration and whether there is any evidence that it shifts over time.
Hippo Skin and Color
A hippo’s skin color is primarily grayish to brownish, with the belly and jaw area often appearing more pinkish. This coloration comes from melanin, the same pigment that gives color to human skin and hair. However, hippos don’t rely solely on melanin to help protect them from the intense African sun.
Hippos also possess a unique natural sunscreen – an oily red-orange substance known as “blood sweat” or “red sweat” that is emitted through their pores. This pigmented sticky secretion gets its color from acid conversion of an orange pigment called hipposudoric acid.
| Body Part | Color |
|---|---|
| Back and sides | Grayish brown |
| Belly and jaw | Pinkish |
| Blood sweat secretion | Red-orange |
Blood sweat acts as an effective sunblock, antimicrobial agent, and skin moisturizer. So in addition to melanin, this unique discharge plays a role in giving a hippo its overall coloration.
Changes in Hippo Coloration Over Time
At birth, baby hippos have much paler skin compared to adults. Their skin is nearly pinkish-white or light gray, without the darker pigmentation developed as adults. After a few months, the skin will start to darken and take on the typical gray-brown hue.
Additionally, hippos living in more shaded regions or those not exposed to as much sunlight appear lighter in color compared to hippos living in sunnier areas. The increased sun exposure prompts the skin to produce more protective melanin.
| Age | Skin Color |
|---|---|
| Newborn | Pinkish white or light gray |
| Juvenile | Dark grayish brown |
| Adult | Grayish brown |
As hippos grow older, their skin also tends to become thinner. An aged hippo may appear to have a more wrinkled look compared to younger adults. The skin can take on a more pinkish tone as it stretches over bony protrusions caused by muscle and fat loss associated with aging.
There is little evidence though that an adult hippo’s skin undergoes any drastic or seasonal shifts in pigmentation. The main color change happens just once, as the baby hippo matures.
Differences Between Hippo Species
There are two living species of hippopotamus – the common hippopotamus and the pygmy hippopotamus. While similar in lifestyle, they differ notably in size and coloration.
Pygmy hippos range from a dark gray to deep purple-brown or even blue-gray. This is a much darker coloration than the common hippo. Pygmy hippos also do not produce the red-orange blood sweat fluid that their larger relatives do.
The coloring likely helps provide additional camouflage for the smaller pygmy hippos in the thick forests they inhabit. Common hippos tend to spend more time in open water and grasslands, so don’t require as dark of a pigmentation.
| Species | Color | Habitat |
|---|---|---|
| Common hippopotamus | Grayish brown | Rivers, lakes, grasslands |
| Pygmy hippopotamus | Dark gray, purple-brown | Forests |
Albino Hippos
While extremely rare, albino hippos have been documented in the wild. These hippos have a genetic mutation that prevents any melanin at all from being produced, overriding the normal dark pigmentation.
Instead of having the typical hippo coloration, albino hippos appear bright pink or even white, especially when young. Their eyes may also appear red. As the hippo ages, it can become more difficult to spot albinism if the skin takes on a darker brownish color with thickening and wrinkling.
The lack of protective melanin makes life more challenging for albino hippos. Without camouflage they are more vulnerable to threats like sunburn, skin infections, and predators. This makes survival to adulthood very difficult.
| Skin Feature | Normal Hippo | Albino Hippo |
|---|---|---|
| Color | Grayish brown | Pinkish white |
| Eyes | Brown | Red |
| Survival Rate | High | Low |
Causes of Skin Color Changes
While hippos don’t normally exhibit major changes in skin color as adults, there are some conditions that can lead to abnormal coloration.
Sunburn – Hippos with severe sunburn may take on a reddish tinge and eventually peel, revealing lighter skin underneath. This is usually temporary as the skin tans again with further sun exposure.
Injury and Scarring – Wounds, scratches, and scars on a hippo’s skin may appear lighter in color initially. As they heal, the skin around the area darkens.
Microorganisms – Certain types of bacterial, fungal, or algal growth on the skin can cause discolored patches, such as red, white, or green spots.
Hippo Pox – This viral skin disease causes red-orange wart-like growths that can proliferate and cover large areas. It does not directly alter the skin color itself though.
Mud Baths – Hippos commonly coat their skin in muddy wallows. As the mud dries and cakes onto the hide, it can mask the typical grayish-brown color until the hippo cleans off in the water.
Conclusion
In summary, hippo skin color is primarily attributed to melanin pigments and unique oily secretions. Baby hippos are born with much lighter skin compared to juveniles and adults. There is also some evidence that environmental factors like sun exposure intensity and habitat light levels can lead to subtle variations in shade.
However, wild adult hippos do not normally undergo noticeable changes in skin color with aging or seasonal cycles. Cases of color changes in adults are usually linked to specific skin conditions, injuries, or microorganism colonization. Very rarely, hippos with albinism may exhibit pinkish-white skin and red eyes due to an absence of melanin.
So while hippo calves lighten up as they mature, full-grown hippos tend to maintain their characteristic gray-brown hue throughout life.