1. Which Parts of a Curled Pangolin Are Covered by Scales?
When a pangolin is attacked, it curls its body into a ball. Its head, back, sides, and the outer parts of its limbs are covered in scales that look like pinecones [2]. When the animal curls up, only the hard, sharp-edged scales face outward [1].
The English name "pangolin" is said to come from the Malay word "pengguling," which means "one who rolls up" [1]. The name itself describes the animal's main defense technique.
The scales do not cover the belly, the inner sides of the limbs, or the soles of the feet [1]. The soft belly is hidden inside when the animal curls up.
When threatened, a pangolin rolls into a sphere. Only the hard, sharp-edged scales face the outside [1].
2. What Material Are Pangolin Scales Made Of?
The material of the scales is keratin. Human hair and fingernails are also made of keratin [1][4].
Just as fingernails grow back after being cut, pangolin scales continue to grow throughout their lives. They keep growing to make up for what wears down [1]. You can think of the pangolin as an animal that wears a hard armor and slowly rebuilds it with every use.
However, think about the shape of a fingernail. You cannot bend a hard nail into a ball. Why can plates made of the same material move with the body as it curls?
3. How Do Overlapping Scales Prevent Gaps?
The answer seems to lie not in the plates themselves, but in how they overlap vertically and horizontally. If you place playing cards side by side without gaps and try to bend them, gaps appear on the outside. But if you stagger them slightly and overlap them, no gaps appear when bent. The way pangolin scales overlap is similar to this. However, the scales actually overlap both vertically and horizontally.
According to a study of the Chinese pangolin and the African tree-dwelling pangolin, each scale is positioned at the center of the surrounding scales, which are arranged in a hexagonal pattern. The inner side of a scale partially covers the three scales below it, and the outer side is partially covered by the three scales above it [1]. This overlapping ensures the skin remains fully covered even when the body moves or curls [1].
The scales slide and shift, forming a flexible protective surface. It is explained that even when curled, it is difficult for skin to be exposed between the plates [3].
If the plates were just hard, they might crack. What is inside the scales?
4. How Do the Layers Inside a Scale Redirect Cracks?
The inside of a scale is divided into three regions. It consists of layers where flat keratin cells are densely packed, but the direction of the cells changes depending on the location [1].
When there are layers with different orientations, the direction of a crack can be bent. This structure is described as hard to pierce and able to absorb force. This high toughness is said to come from the arrangement of the keratin [4].
There is another condition for this toughness: moisture.
5. How Does Moisture Make Pangolin Scales Tougher?
The mechanical properties of the scales are greatly affected by moisture content. There are reports that high humidity makes it harder for cracks to spread [4]. This is similar to how dry fingernails are brittle, while moist fingernails are tough.
Small plates made of the same material as nails form a protective armor by borrowing the power of staggered overlapping, internal layers, and moisture. These features help the scales protect the body as it curls up.
Things You Can Try or See
What you can do today: Prepare about 10 paper cards or sticky notes of the same size. Tape them to a plastic bottle in two ways: first, place them side by side with no gaps; second, stagger them slightly and overlap them over the same area. Compare how gaps appear in each case.
What you can see when you go out: If you find a pinecone, observe how its scales overlap. Pangolin scales are described as pinecone-like. Compare how they overlap.
Official information: Read descriptions of pangolins at zoos or in encyclopedias to learn more about how their scales overlap and how they curl up.