Researchers measured seal depth by using the “depth rod” of a digital caliper. With “healthy” sheds (left), seal depth is measured to the highest point on “convex” seals. For “unhealthy” sheds with concave seals that are recessed or hollowed out (right), the caliper blade is placed in the deepest point of the seal and measured to the highest point. This produces a negative seal depth measurement. It’s a good sign if most of the sheds you find each year look like the shed on the left, with a convex or protruding seal.
