Pinniped Morphologic Assessment: Pre-Necropsy

With the ice seal stranding season currently underway, knowledge of how to properly necropsy pinnipeds is of primary importance and thus will be my foyer into functional anatomy. Referencing Pugliaries as was done in the first entry, I began on external examinations. Since otariids are not found in the North Atlantic, this entire entry will apply only to phocids, as there are morphological differences that cannot be generalized to both families.

Assessing the condition of a pinniped carcass is a necessary pre-necropsy step, as this can dictate which tests can be done. For example, bacterial tests may only be done on fresh carcasses due to a high probability of contamination in moderately or heavily decomposed specimens. There are five code categories that a stranded seal may fall under:

Code 1: Alive.
Code 2: Fresh carcass
Code 3: Moderate decomposition
Code 4: Advanced decomposition
Code 5: Mummified or skeletal remains

Distinct morphological changes accompany each respective stage, such as bloating evident in moderate decomposing individuals. This can be exhibited by a protruding penis or tongue, and is further differentiated from a fresh carcass by dry mucous membranes, cracked skin and a mild odor. Advancedly decomposed specimens may be found intact, but are severely collapsed, have liquefied internal organs and emit strong odors. Scavenger damage is also often apparent. Mummified or skeletal remains are self-explanatory.

Nutritional Condition: By observing the neck and pelvic regions of a stranded pinniped (deceased or alive), a general assumption about that animal's nutritional condition can be made. This spectrum can range from robust to thin to emaciated. Emaciated individuals exhibit conspicious ribs, protruding pelvic bones and have a visible neck. A healthy, robust individual will appear rounded and have a fusiform body shape. In thin animals, the neck and pelvic bones will show slightly. Blubber thickness measurements will further elucidate any nutritional deficiencies during the necropsy.

Sex Determination: The gender of a specimen can be determined by examining the animal ventrally. Lactating females have two horizontally spaced, off-centered teats found caudal to the umbilicus. These mammary glands are not always conspicous and may be obscured by pelage. Non-lactating females have even less obvious teats, sometimes only observable as spots of baldness. Females have two openings, the anus and vagina, in the peri-anal region found near the hind flippers; males only have an anal opening. The penile opening can be found on the ventral midline caudul to the umbilicus, as is true for females. Further help in determining sex can be given by palpating the ventral surface in search of the os penis.

Integument Analysis: The final external assessment before necropsy involves a thorough examination of the pelage, skin, orifices (ears, eyes, etc.) and genitals. Discharge, swelling, lesions, parasites, mucus membrane color, missing teeth, etc. should all be noted. Mammary glands should be palpated to express milk, color, consistency and amount (in cc's) also noted. Regions commonly affected by human interaction such as the peduncle, axilla, or snout should be given particular attention. Skin from between the 1st and 2nd digit of the left rear flipper should be removed, 2 inches the standard amount. The entire lower left jaw is also removed for aging. By cutting the mandibular symphysis from the rostrum to the last post-canine teeth (front of snout to throat), the left mandible can then be dislocated from the zygomatic arch through the trimming of connective tissue and muscle.

In the next few days I will be researching internal examination, utilizing Dierauf, L.A. in addition to Pugliares, K.R.