Extracting the first premolar

Like the rings of a tree, the bear tooth also has rings that can tell us the chronological age of the bear. By cutting a cross section of the tooth root we can count the rings under the microscope.

For consistency, we use the first premolar, which is the first molar behind the canine. The Wisconsin Department of Natural Resources has an excellent webpage showing the best way to remove the tooth: https://dnr.wisconsin.gov/topic/hunt/beartooth.html

Diagram of bear kidney location

Locating the kidney

It can be a challenge to find the kidney. It is usually surrounded by large amounts of fat tissue, is a lot smaller than what most people expect, and it looks different from a human kidney. The kidneys are located near the lower back and when removing the intestines while dressing the animal, they are usually coming out as well.

Instead of a smooth organ, the bear kidney consists of tightly connected lobes covered by a membrane. The kidney often has a light purple appearance.

The size of the kidney depends on the size of the bear, but the length ranges between 6 and 10 inches.

Taking a kidney sample

The easiest way to take kidney samples is to cut out one of the lobes of the kidney and subsequently cut the lobe into 3 equal pieces.

A bear kidney

The first piece will be used for DNA isolation. It is transferred to the vial with the blue label. The vial contains silica gel, which draws out the moisture and keeps the DNA stable.

The second piece will be used for RNA isolation. It is transferred to the vial with the white label. The vial contains a high salt buffer that prevents enzymes from breaking down the RNA.

The third piece can be discarded.