Forensic scientists, crime scene investigators (CSIs), pathologists, archaeologists, paleontologists, biology students, medical students, science teachers, as well as bone and skull-collectors all require skills in working with and in preparing animal or human bones and skeletal remains. Here you will learn to prepare a medium-sized animal skeleton for display. The process you will employ can be used to prepare animal skeletons of all varieties and sizes. Once you have prepared several skeletons, you can compare anatomical structures between different individuals within a species as well as the differences between skeletons of entirely different animal species. You will use these introductory skills in future skeletal preparations of other animal species such as fish, birds, and reptiles. Many of these techniques are used in preparing dinosaur skeletons and other fossils.
Things You’ll Need
A dead animal (road kill, ex-pet, hunting quarry)
Skeleton Preparator’s Standard Toolkit as follows:
Disposable surgical masks
Shovel
Bricks and boards (scrap lumber)
Cotton rags
Old nylon stockings or pantyhose
Bag or bucket of sand
Disposable gloves
Tweezers and tongs
Chlorine bleach
Hydrogen peroxide
Anatomical skeletal diagram
Sieve or old screen
White craft glue
Glue gun and glue sticks
Rubber bands (assorted)
Toothpicks & match sticks
Wooden clothes pins
Cotton swabs
Plaster of Paris
Wire coat hanger
¼-inch wooden dowels
Drill and ¼-inch drill bit
Wooden base.
Step-By-Step Instructions
Step 1: Obtain Carcass. Select and obtain a suitable medium-sized dead but not mangled animal carcass. Non mammals, very large, and very small animals are not suitable for a first-time preparation. Select a medium sized dead animal carcass such as raccoon, opossum, woodchuck, marmot, house cat, or rabbit. Fresh killed and minimally damaged road kill animals are readily available in most areas. Hunting quarry or dead house pets are other possibilities.
Step 2: Prepare Carcass. Prepare your dead animal carcass for a special decomposition burial process by placing it inside of an old nylon stocking or pantyhose to prevent loss of small bones and teeth. Wrap the bundle loosely in a thin old cotton rag with a few holes in it. This preparation wrap will allow decomposition organisms (bugs, worms, bacteria, etc.) access but will prevent loss of any of the small bones or teeth that are loosened during decomposition. Set the prepared carcass bundle aside while you prepare the burial chamber where decomposition will take place.
Step 3: Prepare Burial Chamber. Prepare a special burial chamber to receive the prepared carcass. Locate the burial chamber away from and down wind of dwellings. Dig a hole in the ground that is large enough to accommodate the carcass bundle. A cubic hole with dimensions of roughly two feet by two feet by two feet will be perfect for most medium sized animals. Line this chamber loosely with scrap lumber and bricks arranged so that you can place a wooden cover over the burial chamber. Alternate above-ground burial methods include a big wooden box or heavy cardboard box full of sand or successive bins full of blow-fly maggots and others in a series of decomposition larvae. Frequent watering of the burial chamber, especially in very dry environments, will accelerate soft tissue decomposition and prevent mummification of the remains.
Step 4: Bury Carcass. Place the wrapped carcass bundle inside the completed burial chamber. Add a few spades full of activated compost, sand, or garden soil to cover the carcass but not enough to fill the chamber. The addition of urine, manure, and sour dairy products to the soil will help induce bacterial decomposition. Nature will take care of the rest. Place the wooden cover (lumber scraps) over the chamber and cover with remaining soil. Place a large rock on top to both mark the location and to prevent scavengers from entering.
Step 5: Await Decomposition. Wait for full soft tissue decomposition to take place. Timing will depend upon the size of the animal, your climate conditions (heat, moisture, time of year), and the amount of fat the animal had. Fat tends to impede the process of decomposition. Wait about 60 days in the northern temperate summer or during southern winter months. Wait about 30 days in southern sub-tropical summer. For reference purposes, it takes less than two weeks for a raccoon to decompose to little more than bones on the ground surface during the hot humid Florida summer.
Step 6: Exhume Remains. After the elapsed time, carefully exhume the skeletal remains from burial chamber. If you smell putrification (rotting meat), stop and reseal the burial chamber for a few more weeks. You should smell soil and moldy decay but not putrification when decomposition is sufficiently advanced. Wear disposable rubber gloves. Place the carcass bundle with its contained remains on a work surface and open carefully. You should see bones and some remaining shreds of hair and soft tissue.
Step 7: Gather & Clean Bones. Use tweezers and tongs to remove bones one by one to a bucket containing a gallon of water and two cups of chlorine bleach. Have an anatomical diagram of your skeleton’s species on hand to help you identify and locate the bones as you disarticulate the skeleton. Take notes and sketch diagrams as you continue collecting bones from the animal remains to help you remember how to reassemble the skeleton later.
Step 8: Collect Teeth & Small Bones. Be very careful to gather any teeth which may come loose from the skull and jawbones. Place teeth and very small bones recovered in separate containers of bleach and water to aid in finding them later. Keep the tiny bones from each of the four feet in four separate containers to avoid mixing them up and to ease reassembly later. Leave all bones in their bleach solutions for at least 48 hours.
Step 9: Rinse & Dry Bones. Rinse bones through a sieve or old window screen with much clear water while being very careful not to lose any bones or teeth. Manually remove any shreds of remaining soft tissue using tweezers and tongs. Soak rinsed bones in a bucket of clear water and 2 ounces of hydrogen peroxide for 24 hours to whiten further and to stop bleach reaction. When all bones are recovered and thoroughly rinsed, lay them out on a board or cardboard work surface to dry in the sun. Begin organizing the skeleton as you lay out the bones to dry. Keep the four sets of tiny foot bones separate. Allow bones to dry for two days in the sun. Bleached bones will continue to whiten as they dry. They will have the distinct odor of bleached dried bones, which is the same for all mammals. The odor will dissipate in a few weeks.
Step 10: Assemble Skull. When bones are completely clean and dry, reassemble the skull using white craft glue to re-insert teeth into their sockets. Use glue to assemble both halves of the lower jaw and to attach jaw to skull. Use toothpicks or matchsticks to prop the jaws open to about 45 degrees; and use rubber bands to clamp the bones into position while the glue dries.
Step 11: Assemble Backbone & Tail. Reassemble the spinal column by following your notes and anatomical diagrams and inserting each vertebra onto a wire cut from a metal coat hanger or some other stiff but bendable wire. Install the vertebrae in their proper order. When complete the wire will run through the spinal canal. Use a hot glue gun to inject a spinal “disc” between each vertebra and the next. Use craft glue between contact points along the entire spinal column (and tail). Bend the ends of the wire to hold the vertebrae (and sacroiliac portion of the pelvis) tightly in place while the glue dries and ever after. Assemble tailbones separately and attach those too small to fit on the “spinal wire” later.
Step 12: Assemble the Legs. Use hot glue and craft glue as needed to hold these bones together. Attach the ribs to the proper vertebrae and to the sternum as necessary. Use your hot glue gun to assemble the several sternum bones. Clothes pins serve as excellent clamps to hold bones in place as glue dries. Use a mixture of Plaster of Paris and white craft glue to fill in any broken or damaged portions of bones. Cotton swabs make perfect disposable glue brushes. Use the glue-plaster mixture to add structural connectedness and extra support where ligaments used to be.
Step 13: Mount & Seal the Skeleton. Mount the final assembly of the prepared skeleton on a wooden base. Drill ¼-inch holes near each leg position and install 1/4-inch wooden dowels in each hole. Use these posts and glue with temporary rubber bands to support the skeleton’s legs in a normal stance. Use your hot glue gun to attach the two shoulder blades to the outer surfaces of the ribs. Leave the dowels in place even after the glue has dried to add support to your completed skeleton. With practice and experience, you will be able to assemble an animal skeleton that is completely freestanding. Clear coat the entire skeleton with spray polyurethane to seal and restore luster to the bleached and dried out bones.
Trade Secrets
Use your artistic creativity to solve problems of bone preparation and assembly. Use toothpicks, match sticks, cotton swabs, rubber bands, and clothes pins as temporary devices to prop and clamp bones in place until glue dries. Use a mixture of glue and plaster to repair damaged bones and to fill gaps as needed. White craft glue diluted with water and applied with cotton swabs is a great primer for bone surfaces. The combination of glue-bone-plaster is sandable. Some joints are hard to glue together because cartilage is missing from their surfaces. Use your hot glue gun and layers of white craft glue to rebuild missing cartilage and ligaments. Disposable surgical masks with a dab of cologne will help to get you past obnoxious odors in this project and in this line of work.
Warnings
· Wear rubber gloves when handling dead animals and decomposing remains.
· Be extra careful when using strong chlorine bleach solutions. Bleach and bleach fumes are dangerous. NEVER Mix Ammonia and Bleach!
· Hot glue guns are hot! Danger of burns. Adult supervision is strongly advised.
· Boiling of bones takes place only for human remains when facial reconstruction is required immediately for body identification and other CSI Forensics purposes. In general, boiling distorts and damages most bones and is a poor but fast alternate option to enhanced natural decomposition methods.
· Some people have difficulty dealing with such topics as death, decomposition, burying and digging up dead animals, putrification, and decay. If you intend to become a skeleton preparitor, a CSI, or even to complete this project…You will need to get over it. Dig?
· Whether you are religious or spiritual or not, Death, Decay, Decomposition, and even Skeleton Preparation serve to recycle our remains and are one sure way we all will get to be forever.
Sources:
NPS, 2006. Vertebrate Skeletons: Preparation and Storage: Conserve O Gram: National Park Service, 2006.
Skeleton Preparation: IChristian School Biology/Zoology Syllabus.
McQuilkin, Kyle. 1998. AN ARTICULATED PHYTOSAUR SKELETON: PREPARATION TECHNIQUES FROM FIELD TO EXHIBIT. MA Thesis, Texas Tech. Univ. 1998. 120p.
Dermestarium. Stephen H. Hinshaw, Coordinator of Museum Collections,
Mammal Division University of Michigan Museum of Zoology.
SKULL PREPARATION. Will’s Skull Page: www.skullsite.co.uk
Skull Preparation Stages: A Pictorial Guide: Will’s Skull Page: www.skullsite.co.uk.
The Boneman.com A Source of Books on Skeletal Reconstruction
US Patent References: Method for the preparation of skeletal mounts: Lepaw – July 1956 – US Pat. # 2755165.
