How to Clean a Skull
Every year thousands of people hunt and trap in Alaska. One of the small treasures discarded by many of these outdoors people is the skull of the hunted or trapped animal. When clean, a skull is a source of curiosity and wonder - a mirror of an animal's mode of life. Insights into the animal's diet, strength of bite and its specially developed senses, among other things, can be determined from its skull. In addition to enjoying the natural wonder of skulls, a skull collection can be a great addition to a classroom in a variety of courses, including art, science and social studies.
Cleaning a skull is an easy process and can be no more unpleasant than pulling meat off a cooked soup bone. Here are a few suggestions of how to clean a skull for display or study.
The initial step in cleaning a skull is boiling. The hair and hide should be removed. They contain oils that permeate the bone when boiled and the result is a yellow, greasy skull.
If the skull cannot be cleaned soon after the animal's death, freeze it. Rotting skulls are no fun to clean and may cause a revolt in the household. If the skull is malodorous from decay, it will be repugnant during boiling. In this situation, boil it on a camp stove outside, or in the garage, in a castaway pot.
Immerse the skull in water and let simmer. A thawed wolf or bear skull requires 2.0 to 3.0 hours of simmering. Smaller skulls, such as marten, fox or lynx, take about 40 to 60 minutes. Skulls from old age animals often require longer. Frozen skulls will take about 15 to 30 minutes longer. The skull is ready to be cleaned when the muscle pulls off easily. Do not boil the skull too long as this can crack the teeth and soften the bone. It is best to remove the meat and brain tissue while they are still quite warm. Once cooled and dry, thorough removal of tissue is more difficult.
The muscle, if cooked sufficiently, comes off in hunks. Use a small knife (a scalpel works great if you have one to gently scrape away stubborn tissue, but take care not to cut or mar the bone. Nerve and connective tissue can be teased out of holes and crevices with a wire or large tweezers. The tough part is cleaning inside the cranium (brain case). This is done through the oval opening at the back of the skull, where the skull attaches to the spine. On a bear or wolf, a small spoon is handy for scooping out the brain. Running a stiff wire or small knife around inside the skull, between the brain tissue and bone, helps loosen it and sometimes it will come out in large pieces. With smaller skulls, a large tweezers for teasing out brain tissue works as well as anything. Repeated rinsing flushes out loose tissue.
There are scroll-like, delicate bones in the nasal cavities of mammals. If you want to keep them in the skull, work gently with them. Flushing water through the brain cavity and nasal cavity will work out some of the residual tissue in these bones.
After the skull is as clean as you can get it, soak it in an enzyme-bleach powder (such as Biz) using about ¾ cup to a gallon of water. Don't use liquid bleach, it is harsher to the bone and does not have the enzyme action that is needed to break down residual tissue. Leave big skulls (bear, wolf, caribou, bison) in this solution for 3 days. Smaller skulls may require less than 1 ½ days. The skull has soaked long enough when the remaining tissue can be easily removed.
A small, stiff-bristled brush, a small knife (scalpel) and tweezers are adequate tools for doing the final clean up. Rinse the skull well after you have removed the last, stubborn tissues.
Teeth will invariably loosen during boiling and cleaning. Hang on to them and glue them back in place with white glue once the skull is clean and dry. The skull should be completely dry if it is to be stored in a box or plastic bag.
In the Alaskan interior the dry climate makes it trickier to preserve a cleaned skull. The teeth in particular become very brittle and cracked. Boiling and soaking should be done at absolute minimum times to reduce excessive cracking of bone in dry climates. Once the skull is clean and dry it can be sealed with varathane to help retard cracking but it may turn yellow from the spray. Spray (or paint) the skull with 2 light coats and 1 final, thick coat of varathane. Painting the teeth and skull with diluted, white glue before applying varathane helps too. If teeth start to crack, try filling the cracks with super glue to reduce further fracturing.
If you decide you want a skull or two, there are a few things to remember before you begin the search for specimens.
- Check the regulations. Some species are protected by state and federal laws, and it is illegal to possess any parts of these animals. Examples are bald eagles, any birds protected by the migratory bird act, and marine mammals. Skulls of most animals taken during established hunting seasons within state and federal regulations are legal to possess.
- Make sure that, for species which require it, the skull has been sealed by a representative of ADF&G. Once the skull is cleaned, the seal can be removed.
- Skulls, of some species, like some other animal parts, cannot be sold, purchased or bartered. A hunter or trapper can give you a skull but, again, check the sealing requirements for that species.
- Don't kill animals just for skulls. This could be considered wanton waste, which is a misdemeanor.
- Handle carnivore skulls from the western and northern coasts of Alaska using gloves, preferably disposable ones. There have been several cases of rabies reported from these areas particularly in wolves and foxes. Once the skull has boiled for about 30 minutes the rabies virus will be destroyed.
- When in doubt about possession or legality, call the Department of Fish and Game or Alaska State Troopers, Bureau of Wildlife Enforcement.
Sources of Skulls (skulls will probably need to be cleaned)
- Hunters and Hunting Associations
- Trappers and Trappers' Associations
- U.S. Fish and Wildlife Service
For educational purposes:
Alaska Department of Fish and Game
P.O. Box 25526
Juneau, AK 99802