A whale of a job; Part IPosted on 09-08-2017 by Becky Desjardins
The vertebrate department has undertaken the task of cleaning our dirty cetacean skeletons over the next few years before they are moved to their space in our new collections storage building. In this blog we will be documenting some of the techniques we use as well as some of the cool things we find while doing this project. It is sure to be a whale of a job!
Whale, dolphin and porpoise bones (cetaceans) are a funny thing. They aren’t like other vertebrate bones in that they are extremely porous, and these small holes are filled with fat. Cetaceans actually carry 50% of their fat under the skin as blubber, and 50% in the bones. This makes them very challenging both to prepare and to keep in collections.
To begin to explain why whale bones are such a challenge, we have consider how they are prepared. What usually happens is that a cetacean dies and washes up on a beach somewhere. The Naturalis whale team is dispatched to dissect it. We preserve DNA samples from the tissues, but the bulk of the work is the process to save all the bones: on the beach or dock we remove as much meat, fat, and blood as possible from the bones and then bring them into the museum preparation lab for further work. Currently the method of preparation Naturalis uses is maceration: we put the bones in a bath of 38 degree water for a few weeks to let all the remaining flesh rot off. This method also removes some of the fat from inside the porous bones, but not all. In the past other methods of bone cleaning have included burying in the ground, burying in a pile of horse manure, leaving out for flies to eat...all of these methods have different advantages and disadvantages. Regardless of what method is used, it is extremely difficult to remove all the fat from the center of large, thick whale bones. But, preparators get them as clean and white as possible, and then put them in the scientific collection or on exhibit. In the Naturalis collections, we have hundreds of cetacean skeletons, some stored in a box as loose bones, and some assembled together.
What frequently happens over the years is that the fat remaining inside the bones starts to leak out. The formerly clean white bones turn orange on the surface and eventually darken to brown, and some get sticky to the touch. Besides being a bit disgusting, dust from the air sticks to this gluey surface and mixes with the fat. This creates an acid which over time can degrade the bones. It can really be a problem! Happily, fat damage does not always happen to every specimen, and even on effected skeletons some areas tend to be greasier than others, for example: the tip of the tail and the flippers are more frequently in bad shape than the skull.
How do we clean these dirty bones? Are there different techniques to try? In the next post, we will explain our plan of action going forward on this whale of a job.