This paper provides an overview of marine mammal necropsies — post-mortem examinations conducted on stranded or deceased marine animals. It explains what a necropsy is, how it parallels a human autopsy, and why U.S. law requires that all stranded marine mammals be examined for evidence of human interaction (HI). Drawing on pinniped necropsy technique guidelines, the paper outlines the step-by-step procedure biologists follow, from assessing decomposition code and body condition to organ removal and sample collection. It also identifies which tissues — including brain, liver, kidney, lung, and testicular tissue — are gathered, and for what scientific and public health purposes.
This paper demonstrates procedural synthesis — taking a detailed technical protocol and condensing it into an accessible, logically sequenced narrative without sacrificing accuracy. The writer moves from definition, to rationale, to procedure, to outcome (tissue purpose), modeling the kind of explanatory writing required in applied science courses.
The paper follows a Q&A scaffold across four sections: (1) definition of a necropsy, (2) legal and scientific justification for performing them, (3) step-by-step pinniped necropsy procedure, and (4) tissue types collected and their purposes. This format suits introductory science writing where clarity of explanation is the primary objective. The conclusion is implicit rather than stated — the tissue sampling section effectively closes the loop by connecting physical procedure to scientific outcome.
When biologists wish to determine the cause of death for a marine mammal, they conduct a necropsy. A necropsy is similar to an autopsy performed on humans. The marine mammal must be cut open and carefully examined so that the cause of death can be established. The necropsy helps the biologist understand — through direct observation of the carcass — how and why the animal died, whether public health may be affected, and whether "signs of human interaction are present on the carcass" (Section One, p. 15).
The biologist or scientist performing the necropsy initially makes an objective evaluation to determine whether there are obvious signs that human interaction (HI) may have been involved. A second, more thorough and subjective examination is then conducted to further evaluate the possibility that humans played any role in the marine mammal's death.
First, every stranded marine mammal found on any beach or shoreline in the United States must by law be examined for evidence of human interaction (p. 15). The National Oceanic and Atmospheric Administration (NOAA) requires that HI information be gathered and documented in order to fully explain the circumstances of the marine mammal's death.
Second, necropsies are performed because scientists need to understand all the factors that may explain a marine mammal's death. A "solid scientific foundation" must be established in the interest of wildlife conservation. Carefully examining the types of interactions that occurred between the marine mammal and humans or other animals can "highlight resource use conflicts" (p. 16). This is critically important because data involving human interaction can be "easily misinterpreted," and where powerful evidence exists regarding the cause of death, it must be verified (p. 16).
When conflicts between marine mammals and humans are identified through necropsy, that understanding can lead to "appropriate measures" to resolve those conflicts (p. 16).
The first step is to determine which decomposition "code" applies — that is, how far along in the decomposition process the animal has progressed. The animal's nutritional condition prior to death must also be estimated. Among the questions and issues to be considered are: (a) the animal's sex; (b) whether the eyes are discolored; (c) whether lesions or parasites are present, and what color the nasal discharge is; (d) all abnormalities, including abscesses, wounds, and possible injuries from fishing gear, must be examined and documented; and (e) the fur, skin, genital aperture, and anus must be closely examined and recorded (p. 32).
Next, a two-inch piece of skin is removed near the left rear flipper, and the lower left jaw is extracted to provide the animal's life history. The blubber, muscle, and skin are then removed, after which the front flippers are taken off. The lymph nodes are carefully scrutinized, and the thymus is investigated. A propane torch is used to sear the body, and a sterile blade is employed to ensure that "uncontaminated bacterial and viral samples" can be collected. Finally, the rib cage is removed and the lungs, heart, and other internal organs are assessed.
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