The skeletons of mammals are inherently beautiful. Beneath the ripple of muscle and folds of skin lies the intricate framework that holds organs and protects the brain—a structure both informative and a little mystical.
Let’s say you’ve found a deceased animal and wish to preserve its skeleton, skull, or some other part of its skeletal structure. Before diving in, remember not to handle the animal with your bare hands. It may have succumbed to disease, which could pose a risk to you or your pets. Always wear gloves or use a plastic barrier, such as a bag, when handling it. Once done, wash your hands thoroughly with dishwashing liquid.
The method described here works well for the skeletons of fish, amphibians, reptiles, and virtually any animal with an internal skeleton.
However, extremely thin bones—like those of some fish—can be fragile and may not survive the process.
The technique we’ll be using is decomposition, commonly referred to as “rotting.”
Preparing the Carcass #
The less material there is to decay, the faster the process will be. While this step is optional, for larger animals it can significantly reduce decomposition time. If the specimen is smaller than a cat, you can skip this part. For animals the size of a cat or larger, consider the following:
Using a sharp knife or scalpel, remove as much flesh as possible. Focus on areas like the abdomen, throat, major leg muscles, and the soft tissue between the lower jaw. Remove organs and guts carefully to avoid damaging the bones.
Dispose of the removed tissue as you would any meat scraps. If you’re uncomfortable with this or lack experience, you can skip this step, though decomposition will take longer.
Burying the Specimen #
The next step is burial. Choose a location with dark, moist, and living soil—such as a garden or backyard—with the landowner’s permission. This type of soil is rich in bacteria, worms, and other decomposers, which will assist in breaking down the tissue.
For effective burial, dig a hole at least 70 cm deep. This depth prevents scavengers from unearthing the carcass and keeps it safe from rain exposure. For larger animals, consider digging deeper.
For smaller specimens, use a sturdy, wide-mouthed plastic container. Place the carcass inside and surround it with soil before burying the entire container. For larger animals, line the hole with a sturdy tarpaulin or garbage bags to make retrieving small bones and teeth easier later.
Once the carcass is buried, tamp the soil down lightly and mark the spot with rocks or other markers. Avoid planting anything in this area while the decomposition process is underway.
The Waiting Game #
Decomposition takes time, anywhere from weeks to months, depending on the size of the animal. Small animals like hamsters might be ready in about a month, while larger specimens like a dog or deer can take several months.
You can dig up the specimen periodically to check its progress, though the experience may be unpleasant due to the odour. The skeleton is ready when the bones are fully exposed and most soft tissue has decomposed. Some fur or remnants of tissue may remain, but these can be dealt with in later steps.
Excavating the Bones #
Once sufficient time has passed, it’s time to retrieve the skeleton. Begin by carefully removing the top layers of soil with a shovel, then switch to gloved hands as you approach the bones. Be gentle to avoid damaging delicate pieces.
Mammal skeletons can have over 200 bones, some as small as pinheads. Use a diagram of the animal’s skeleton to ensure no pieces are missed. Sift through the soil or tarpaulin carefully, as finding every last bone—especially small teeth or claws—can take time.
Once all the bones are collected, rinse them in water to remove dirt and debris. Larger bones can be soaked in a bucket, but smaller ones should be placed in individual containers to avoid losing them. Use a brush to clean stubborn bits of debris, but handle fragile bones like skull structures with care.
Cleaning the Skull #
If you’re working with a skull, particularly a large one, you may find that the brain is still intact. Use a wooden tool, like a chopstick, to gently stir and remove the brain through the opening at the back of the skull. This can be an unpleasant but necessary task.
After removing as much as possible, soak the skull in water again and clean out any remaining bits. Plant roots or debris caught in crevices should be removed with fine tweezers. This process can feel tedious but is meditative for some.
Degreasing with Soap #
Once the bones are free of debris, it’s time to remove remaining fats. Prepare a warm, soapy solution using unscented dishwashing liquid. Avoid boiling the bones, as high heat can damage them. Instead, soak them in the warm solution and agitate occasionally.
You’ll notice oils and grime floating to the surface as the soap emulsifies fats. Continue soaking until the bones appear clean. This process may take several hours and can be repeated if necessary. Rinse the bones thoroughly in lukewarm water afterward and allow them to dry completely.
Whitening #
To achieve a brighter appearance, bones can be whitened using hydrogen peroxide. A 3.5% solution, available at most drugstores, works well. Submerge the bones in the solution, keeping a close eye on them, as they will begin to whiten quickly.
Remove the bones before they become overly white, as excessive bleaching can make them appear unnatural. Rinse thoroughly with water to remove any residual hydrogen peroxide. The solution can be reused, though it will lose potency over time.
The Final Touch #
Once the bones are clean and dry, you’ll have a beautifully preserved skeleton or skull. For loose teeth or disarticulated jawbones, use PVA glue (wood glue) to reassemble the pieces if desired.
Your finished piece can now serve as a lasting and fascinating addition to your collection or display. Whether you choose to study, display, or simply admire it, your preserved skeleton is a testament to both the complexity and beauty of the natural world.