Grugruk examines the markings closely, trying to think of an animal that may leave such markings
Rolled for a total 32 on Nat lore check
As soon as Grugruk begins to think on what could possibly make those marks, even he is astounded by the veritable index of beasts that filter through his mind.
The small marks seem more like thorny bristle-pads with the thorny-teeth all pointed in the direction to hold a good grip. Likely to improve grip. Some animals have lines or filaments (think gecko) on their hands for such purpose, and some plant-creatures that climb do so with either an adhesive sap, or by grabbing into the material they climb, but none do both.
Most likely: this is man-made, based on such creatures (think the real-world gecko-based climbing stuff).