We have reported recently in the journal Nature Communications that African elephant skin channels are fractures, due to local bending mechanical stress, of the animal brittle and desquamation-deficient skin outermost layer.
The National Geographic reports on our results both in the March 2019 issue and in their video.
More info here on how bending stress generates cracking of the skin.
Locally-Curved Geometry Generates Bending Cracks in The African Elephant Skin
Martins, Bennett, Clavel, Groenewald, Hensman, Hoby, Joris, Manger & Milinkovitch* Nature Communications (2018)
*Corresponding author: email@example.com
Another video summarizing our findings is available here.