How to Keep Skeletons Clean—Just Spit on Them!

In a previous post for the museum blog, I briefly discussed zooarchaeology as an academic discipline and mentioned my desire to foster zooarchaeological research at the Canadian Museum of Nature. We once hosted the Zooarchaeology Research Centre (ZIC), which operated from 1972 until 1996, and the museum continues to house the excellent comparative skeletal material that was assembled by ZIC.

With more than 4500 specimens, representing over 95% of the bird and mammal species known to occur in Canada, the museum Comparative Osteology Collection is an invaluable research tool for archaeological work in Canada.

Several mounted skeletons in the museum's collection.

Skeletons of North American hoofed animals in the osteology collection, including (from left to right) a moose (Alces alces), a juvenile and an adult bison (Bison bison), a muskox (Ovibos moschatus) and a pronghorn (Antilocapra americana). Image: Roger Baird © Canadian Museum of Nature

Since ZIC disbanded, osteological specimens—osteology being the study of bones—have become an underutilized resource at the museum. This pains me, having a research background in zooarchaeology myself, so I have set out on a mission to change the situation.

Part of the plan to resuscitate a zooarchaeology research program here in Ottawa involves expanding the osteology collection, adding new specimens that will increase the representation of Canadian species and also expand coverage beyond North America.

Collage: A room full of metal cabinets, an Atlantic Cod skull, an American bison skull.

View of the Comparative Osteology Room at the museum’s collection and research facility, in Gatineau, Quebec. All of these cabinets contain skeletons that together represent all the major vertebrate groups of Canada. Left: The skull of an Atlantic Cod (Gadus morhua) mounted so that the separate bones are clearly visible. Fish have very complicated skeletons, particularly the skull, so specimens such as this are essential to both teaching and identification. Right: Head of the mounted skeleton of an adult American bison (Bison bison) in the osteology collection of the Vertebrate Zoology section, with the skeleton of a moose (Alces alces) visible in the background. Images: Scott Rufolo, Roger Baird © Canadian Museum of Nature

Zooarchaeologists use osteological collections as references for helping to identify the bones of animals found on archaeological sites, with the ultimate goal of better understanding the relationship between humans and animals over time and in different cultural contexts.

To help me prepare for adding specimens to our collection, I recently attended a workshop and conference in England focused on curating osteological material. Titled Bone Collections: Using, Conserving and Understanding Osteology in Museums, the event was a venue for discussing methods of skeletonizing carcasses. It also provided hands-on training in various techniques for cleaning and caring for bone specimens once a skeleton has been extracted from all of the surrounding soft tissue. I’ll save discussion of how to prepare a skeleton from a fresh animal carcass for a subsequent post, and rather share here some of the tips I learned for cleaning bone.

Drawers open in a cabinet displaying bones cushioned on foam.

A cabinet full of bones—deer skeletons in the comparative collection. Image: Scott Rufolo © Canadian Museum of Nature

Once in storage, bones can become covered in dust or accumulate fatty deposits on their surfaces from the oils that are often left inside specimens following their initial defleshing. If left for long periods of time, this surface debris can alter the chemistry of the bone and harm its structural integrity.

In the workshop, we learned to tackle cleaning a specimen in stages, working first with the more gentle agents and tools and moving on to harsher—but often more effective—treatments where necessary. Brushing and the use of specialized museum vaccuums took care of general dust accumulation, but heavy soiling with airborne debris required smoke sponge and Groom Stick specialized conservation materials that act as molecular traps for removing particulate matter.

For thick layers of congealed substances such as bone grease, we turned to dilute alcohol solutions and industrial detergents. Their usage, however, has to be limited because they can harm some specimens through dehydration.

Collage: The babirusa skull before and after cleaning.

Left: The skull of a babirusa (Babyrousa sp.) prior to cleaning. Collected at the end of the 19th century and stored on an open shelf for decades without treatment, this specimen was dark with accumulated dust. Right: The same skull following my preliminary cleaning during the workshop. Perhaps not yet worthy of exhibition, but certainly looking spiffy compared to its earlier state! Images: Images: Scott Rufolo © Canadian Museum of Nature

The surprise tip of the workshop: use saliva! The enzymes in saliva that help break down food also work well on bone grease and the organic components of dust, and they don’t harm the bone. So, before breaking out the detergent solutions, workshop participants moistened swabs with their own spit and used these first to tackle stubborn accumulations. In a number of instances, saliva alone was sufficient to clean the bone surface. Contrary to what the title of my post might suggest, however, we all had enough couth to not spit directly on our bone specimens.

An array of pinned insects in a tray.

During the tour for conference participants, we saw a collection of beetles assembled by Charles Darwin while he was a student at the University of Cambridge. Image: Scott Rufolo © Canadian Museum of Nature

The conference was held at the University Museum of Zoology in Cambridge, and conference attendees were treated to a tour of the museum’s holdings. I’ll leave you with more pictures of a few of the treasures in the University Museum of Zoology’s collections. Until next time!

An egg in protective foam.

Charles Darwin collected this bird egg (which belongs to one of South America’s tinamou species), and it still bears his signature. The crack—also courtesy of Mr. Darwin—occurred when the egg was being placed into its original container on board the HMS Beagle, the vessel that carried Darwin on his travels in the southern hemisphere during which his theory of evolution began to take shape. It is the only egg collected on the voyage to have survived. Image: Scott Rufolo © Canadian Museum of Nature

Collage: A mounted Dodo skeleton, a Tasmanian tiger skull in a storage box.

Left: One of the great osteological treasures of the University Museum of Zoology is this nearly complete Dodo skeleton. The Dodo (Raphus cucullatus), once found on Mauritius in the Mascarene Islands of the Indian Ocean, is an extinct relative of the pigeon. Right: Ranking alongside the Dodo as a famous symbol of extinction, the Tasmanian tiger or thylacine (Thylacinus cynocephalus) is also represented in the osteological holdings of Cambridge. Shown here is the jaw and cranium of a thylacine pup, quite valuable as examples of young individuals of this animal are rare. Images: Paul Tucker © University Museum of Zoology, Cambridge (Dodo skeleton), Scott Rufolo © Canadian Museum of Nature (Tasmanian tiger skull)

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One Response to How to Keep Skeletons Clean—Just Spit on Them!

  1. Pingback: Of Fish and Men…Studying Fossil Fish in Ethiopia | Canadian Museum of Nature – Blog

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