Stranding

This skeleton was a male Atlantic white-sided dolphin (144 cm total length, sample image at right) that was found dead after stranding itself on Cook’s Brook Beach, Eastham, Barnstable Co., MA. While no cause of death could be determined from the necropsy (animal autopsy) performed on the beach, it is thought that this dolphin was a member of a mass stranding. Atlantic white-sided dolphins (dolphin book on sale) typically strand in large numbers, called a mass stranding. These dolphins are social animals and greatly dependent on each other when in deep Atlantic waters. While there is no universally accepted explanation for mass strandings, social bonds may subjugate survival instincts, causing large numbers of animals to follow one dolphin ashore. The occurrence of mass strandings is also attributed to a number of other explanations, such as the hook-like shape of Cape Cod, tidal fluctuations, weather conditions, disease, injury or acoustic interference.

Removing Flesh

This dolphin was sexed, measured and left on the beach with a cattle tag attached to its dorsal so it would not be reported as an another mortality. A month later, the skeleton was salvaged from a still intact carcass. The skeleton was taken to a Wildlife Management Area where it was laid on the ground and covered with a tarpaulin to protect it from coyotes. The skeleton was left outdoors in hot sunny weather. This allowed the carcass to attract flies that laid a large amount of eggs or larvae. The flesh was consumed over the next two weeks by the fly larvae (maggots). It was left under the tarpaulin until late into the summer when it was carefully collected so none of the small bones were lost. At this point the skeleton was roughly cleaned and placed into large bags for storage. This process is simple and effective, but can only be used during the summer when flies are active. The process allows a large number of skeletons to be cleaned with minimal effort and generally does not cause small bones to be lost. This skeleton was meticulously cared for during the flesh removal process and therefore had very few missing bones.

Other methods used to remove flesh from bones include:

• Dermestid beetles: carnivorous beetles eat the flesh from the bones without damaging any structure. The beetles can be found at universities, museums, or supply houses. http://www.boneroom.com/faqs/bones.html
• Maceration: submerging the skeleton underwater for up to 2 weeks to allow the bacterial break down of the flesh. Heated water will speed up this process. http://ag.arizona.edu/pubs/natresources/az1144.pdf
• Placing the bones on a bed of horse manure and covering with manure. This process uses bacteria and heat in the manure to decompose the flesh - it also draws out the oil from the bones, which can be a very real problem with larger whale bones. However, this method is more laborious and makes it harder to retain all of the small bones.

Cleaning

By this point the bones had only small amounts of flesh or ligament attached. To remove this material (and some dirt that remained on the bones) the bones were soaked in warm water for a few minutes and then scrubbed with toothbrushes. Finished bones were placed on the tarp to dry.

In some cases this process was not enough to remove ligaments. To remove tougher material, select bones were boiled in a large pot on a stove. To avoid damage to bones due to temperature change, the bones were first placed in hot tap water and then were moved into the pot of water before it reached boiling. Bones were boiled until the remaining tissue was soft and could be removed with pliers. The finished bones were then laid out to dry.

Since the vertebrae had been removed from the flesh in order, they were kept in the correct order throughout the cleaning and bleaching process by tying them together with string in groups of 8 or so. String will not impact the soaking, boiling or bleaching processes and is useful to keep groups of neighboring bones together.

Special care was taken with the teeth. They had arrived in order and attached to the jawbones. To keep the teeth in order, four grooves were cut in a styrofoam block. Each groove was labeled to correspond to one side of a jaw (e.g., ‘Upper Left’). The teeth were then removed from the jaw and placed in the appropriate section of styrofoam. Each tooth or empty tooth socket was numbered to keep order accurate. Any displaced teeth were compared to teeth with a known location until they could be correctly placed.

Bleaching

Once the bones were cleaned, most were still discolored and needed to be bleached. To bleach the bones they were soaked in peroxide. The most accessible peroxide source is 20 or 40 Volume Liquid Developer (6% and 12% peroxide respectively) that can be found at a beauty supply store or online. It would be ideal to use a 35% peroxide solution, however this concentration is not always available commercially. Approximately 30 gallons of 20 Vol Liquid Developer were needed to bleach the dolphins’ bones. Since peroxide is a strong chemical that can bleach skin and clothing, latex gloves were used and the safety precautions on the bottle were followed.

Larger bones were placed in tubs filled with developer while smaller bones (or bones that needed to be kept together) were placed in small bowls of developer. The bones were allowed to sit in the peroxide for 2-5 days depending on how dark they were originally. Many of the darker bones needed to go through 2-3 cycles of soaking in fresh tubs of developer since the peroxide deactivates over time and with exposure to light. Once bones were acceptably pale, they were placed in tubs of water for several days. The water would be changed every day or two. Once the bones were clean of peroxide they were laid out to dry on paper towels or trash bags for several days.

Assembly

Now that the bones were white and dry, it was time to begin assembling the skeleton. To assess the size of the skeleton and to determine if any bones were missing, the skeleton was laid out on a table with the vertebrae, chevrons, and ribs in order. These bones were numbered anterior to posterior with a pencil. This was done by consulting images online. Once the skeleton was in order, it was clear that many bones and several teeth were missing. To complete the skeleton it was necessary to create replacements using existing bones. To do this, Resilpon Silicon Mold Making Putty was used to create a mold for the missing bone. Once dry, the mold was filled with Compleat Cast 2 Part Casting Resin to create an exact replica. Other bones were sculpted by hand using Magic Sculpt Hardener and Flesh Resin. All casting products were supplied by The Compleat Sculptor, Inc. Many of the inter-vertebrae disks had separated from their respective vertebrae and these were matched and glued on using Lineco Neutral pH Adhesive.

Once all the missing bones had been made, all bones were marked with a pencil to show where they needed to be drilled. Since most bones would be attached with wire, it was key to make sure the holes on adjacent bones were correctly aligned. The vertebrae were marked in the center on each side where they would connect to each other. To connect the vertebrae to the ribs, the vertebrae 5-19 were marked at the ends of the transverse processes, as well as on the peduncle for vertebrae 4-9 (this occurs since the first 5 ribs attach to the transverse process of one vertebrae and the peduncle of the preceding vertebrae). The ribs were marked to match the vertebrae holes and also at their ventral ends where they would be wired to the floating ribs.

All these marks were drilled with a 5/16th bit in a drill press for the central vertebrae holes, and with a 1/16th bit in a hand drill for the other holes. Some of the smallest vertebrae in the tail were also drilled with this bit size.

The flippers were assembled by drilling 1/16ths hole through each bone, or by drilling 2cm into adjacent bones and anchoring a short piece of wire into each bone using hot glue. Gaps were left between bones and were filled with fake cartilage.

The spine could then be assembled. The smallest vertebrae that were drilled with 1/16th holes were threaded on a wire separated by cartilage made from the Magic Sculpt Hardener and Flesh Resin. The rod for the spine was bent to have a slight curve and then the vertebrae were slid onto it starting at the posterior end. The vertebrae were separated by ~0.5cm of cartilage. Once the vertebrae cartilage was dry, the ribs were attached to the vertebrae by wire that was twisted into a spiral at each end so the wire wouldn’t pull through the hole.

To complete and attach the skull, all the teeth were first glued in with hot glue or Neutral pH Adhesive. Missing socket separations were replaced with Sculpt Hardener and Resin. The lower jawbones were drilled at their most rostral tip and wired together. On the top of the jawbones just before where the teeth begin, another hole was drilled which was then wired up through a pre-existing hole in the skull to provide support. The jawbones were attached to the skull by wires that went through the most posterior part of the jaw and through the jaw joint in the skull. The skull was attached by soldering two 4-inch 5/16ths threaded rods onto the rod with the rest of the vertebrae such that this prong structure could be inserted into the opening at the back of the skull. The rod and prong structure was placed inside the skull and the open space was filled using Good Stuff Spray Foam Insulation (Windows and Doors).

To complete and attach the sternum, chevrons and flippers, the skeleton had to be hung. The sternum bone and floating ribs were attached to the ribcage using 1/16th wire. The ribcage originally lacked shape and stability, so wire was wrapped around each main rib, which was stiff enough to hold the ribs out and in position. The sternum was tied to the vertebrae with monofilament to provide extra support. At this point, it became possible to determine where the scapula would be located so the scapula was drilled and attached to the ribs with wire in two places. The flippers were then attacked to the scapula with wire and were positioned using monofilament that was tied to the ceiling.

The chevrons were attached using monofilament strung through holes drilled at the chevron tips. The monofilament was tied tightly around the cartilage that each chevron was beneath. The monofilament was painted to match the cartilage.

Throughout the entire assembly process, as bones were created or molded they were painted a pale yellow/white color that matched the original bones. All cartilage that was made was painted a gray color. All monofilament knots were hot glued in place (although if thinner monofilament had been used it would be ideal to melt the knots instead).

Materials and Procedures

Cleaning

Buckets/tubs large enough to soak bones in water

Tarp to perform project on

Toothbrushes (4 soft bristle) for scrubbing bones

Thin pliers to help pull off flesh

Pots large enough to boil any bones still attached to flesh

String (optional) to tie together vertebrae or other bones

Scissors for scraping flesh off bones and cut string

Latex gloves (needed for cleaning and bleaching)

Styrofoam blocks to use as props and for organizing teeth

Bleaching

Tubs large enough to soak bones

Small bowls to soak any small bones you want to keep together

Peroxide; preferably 12% (try 40 Volume Liquid Developer) to whiten bones

Paper towels for drying bones

Trash bags to place peroxide-covered bones on

Casting

Hot glue gun

Magic Sculpt Hardener

Magic Sculpt Flesh Resin

Compleat Cast 2 Part Polyurethane Casting Resin Tan Part A & Part B

Resilpon Silicon Mold Making Putty

Assembly

Table to lay out skeleton on

Pencil

Scissors

Hot Glue Gun

Threaded Metal Rod (~8 ft of 5/16th inch was used)

Drill (Hand and Drill Press) with clamps, wood blocks, etc

Drill Bits (5/16ths and 1/16ths)

Monofilament (17 lb test)

Wire (16 and 20 gauge galvanized steel)

Needle nose pliers

Good Stuff Spray Foam Insulation (Windows and Doors)

Lineco Neutral pH Adhesive

Soldering gun

Paint (bone color and cartilage color)

Resources

• http://www.sculpt.com/ Great source for casting and molding tools and materials. This project aquired a variety of products from Compleat Sculptor including the Magic Sculpt Hardener, Magic Sculpt Flesh Resin, Compleat Cast 2 Part Polyurethane Casting Resin Tan Part A & Part B and Resilpon Silicon Mold Making Putty.
• http://www.theboneman.com/spermwhaleskeletons.html This book was used to gain information on the articulation process and bone types/locations. This version is most helpful for cetaceans, but other volumes exist for different skeletons.
• Timmerman, John. “Seal/Dolphin - Phoca/Stenella: A Skeletal Comparison of Two Marine Mammals.” The North Carolina Fossil Club, 1997. This book was a great resource for what different bones looked like and where they went in the skeleton. The images are all drawn, but were very helpful.
• http://www-adm.pdx.edu/user/bio/articula/home.html The Articulation Page describes the articulation process and provides methods for cleaning and assembling skeletons. Some visuals are included.

Acknowledgements

Stephan Gersh

Tom French

Marc Fields

Judith M. Chupasko

Everyone at the Whale Center of New England!