Noel Lyon – BRTC intern
One of the more hands on tasks at the Biodiversity Research and Teaching Collections (BRTC) is to prepare scientific specimens to be cataloged into the mammal database. Scientifically prepared skins held in natural history collections provide morphological and physical characteristics of individuals and the species as a whole. These data can illustrate how individuals and a species can vary through time and geography, creating a snapshot of a species in a given time and location. Furthermore, additional data such as the life stage, tissues, and parasites gathered during the collection of a particular specimen can also provide researchers with useful data.
During my internship, I prepared several specimens in the order Rodentia. I did not have trouble skinning after receiving excellent instructions provided by Dr. Light. But stuffing specimens proved to be a challenge. Skinning of all mammals follows a general procedure that can be altered depending on the desired outcome (pelt, museum specimen, meat). A cut is made up the ventral side of the body from just above the urogenital area to about the forelimbs. This allows room for the skin to be worked off the limbs and body using a counter pull system. This system involves pulling the body one way while simultaneously pulling the skin in the opposite direction. Extra care is taken around the limbs and tail to prevent the skin from tearing. Similarly, the face needs to be worked off of the skull very carefully to ensure that the nose, ears, and eyes remain intact. The bones that comprise the digits and feet on the right side of the animal, as well as the baculum for males, are kept in the skin to maximize the amount of information that the specimen provides.
Wire is traditionally placed in the tail and limbs to ensure that these portions of the specimen are laid out straight. Small specimens such as mice require very thin wire, which unfortunately is easily bent. I found inserting the wire into the right forelimb and hindlimb to be the most difficult and sometimes frustrating part of preparing a specimen. Wire is inserted in the feet so that it sits between the bones and the skin. There is very little room in this area, and inserting the wire requires gentle poking and manipulation to slide into place. Cotton is often wrapped around the section of wire that sits in the area of the legs vacated by the femur and tibia in the hindlimb, or the humerus, radius and ulna in the forelimb. This is done to give the prepared skin as much of a lifelike appearance as possible.
Cotton is also wrapped around the wire used in the tail. The process of inserting the wire into the tail is much easier than in the limbs. However, the cotton must be wrapped very tightly around the wire or it will slip and bunch up which makes insertion impossible. Additionally, the thickness of the cotton must taper towards the tip of the tail, with it being widest at the base of the tail.
Cotton is also used to stuff the body cavity and head of the animal. Cotton has to be placed just right in the nasal region of the animal, otherwise it looks very odd; for rodents, you want the specimen to have a pointy nose just like in life. I found the aid of forceps crucial in this step. After estimating the amount of cotton needed and cutting it into the shape of a triangle, I would fold up one corner very tightly and grasp it with the forceps. After carefully placing this end into the tip of the animals nose, I would release the forceps and the cotton would expand and fill in the nose. After that, I would fold the rest of the cotton into the body and sew up the incisions made during skinning. This step often took the longest, as removing and manipulating the cotton was necessary to ensure that body proportions were more or less realistic, and dorsal and ventral surfaces were smooth. The final step is to pin the specimen to a piece of foam to dry. This step requires an artistic touch to make the animal appear as lifelike as possible. The nose, head, and tail are lined up while the legs are stretched out pointing directly to the front and rear of the animal. Lastly, brushing the fur and minor tweaking can make a huge difference in appearance.
With biodiversity declining around the world, properly prepared and cared for specimens are becoming increasingly valuable. As species become scarce, studying them becomes more difficult. Natural-history collections provide samples of species that may otherwise be unobtainable. Data gathered from prepared skins may provide insight into why a species is in decline in the wild, as well as how individuals vary over time and space.