Displaying items by tag: porpoise

The special sensory organs in cetaceans include the eyes, ears, and echolocation system. Unlike pinnipeds, cetaceans spend all their time in the water so their sensory systems do not need to function as well in air. Indeed, as fully aquatic animals, cetaceans have become superbly adapted to take advantage of the physical properties of water.

Him or Her? Gender is one of the most important elements of the level A form and determining he or she is quite different in a cetacean than pinniped. In general, most cetaceans do not have the obvious secondary sexual characteristics such as the raised bony CREST that you find on the forehead in male California sea lions. Cetacean males also do not have a baculum, or bone in the penis, which is readily distinguishable even after extreme decomposition. Rather, body size tends to be the biggest difference between male and female cetaceans and often even this is not readily distinguishable. Thus, gender determination in cetaceans usually relies upon examination of the ventral body surface.

In cetaceans, length is usually the first and main clue as to the relative age of an individual and this will of course be species specific. At the bottom of this page you can find standard lengths for various age classes for Atlantic harbor porpoises from the published literature.

Watch the stages of decomposition from fresh dead (condition code 2) to advanced decomposition (condition code 4) to skeletal (condition code 5).  These images are all of harbor porpoises that stranded in Santa Cruz, CA.  Check out the stages of decomposition for a sea lion here.

The process of postmortem tissue decomposition is also called AUTOLYSIS ("auto"= self and "lysis"=breakdown). It is caused by a number of factors including ENZYME LEAKAGE, INSECT ACTIVITY and BACTERIAL ACTION.

How do you tell a lesion or injury from damage done by scavenging? Even before an animal hits the beach scavenging by everything from sharks to birds to the neighborhood dog may cause damage to the carcass. While this is nature’s best recycling program, it can be difficult at times to tell normal scavenging from pre-mortem injury or pathological lesions.

How fresh is that carcass? The answer to this question will determine how much information you can potentially get from the animal and what kind of follow up exam you should potentially do. Fresh animals will be candidates for a full necropsy while code 3 or 4 animals may be better suited for a beach necropsy or simple exam.  After reviewing the condition codes be sure to test your knowledge by taking the condition code QUIZ!