Necropsy: A Valuable Tool

By Pauline Baker, Think Wild

Every species has anatomical differences that enable them to have specialized life histories. Knowing these differences is imperative for successful rehabilitation of wild animals. Necropsies are a valuable tool in helping wildlife professionals learn these anatomical differences and apply them to species specific protocols, inevitably improving the overall care of wildlife admitted to rehabilitation hospitals. Necropsies also provide clues or, in some cases, answers to questions about the causes of mortality of wildlife admitted into rehabilitation centers, and can assist in disease monitoring in wildlife populations. This helps in potentially preventing wildlife mortalities in the future.

For the Oregon Wildlife Rehabilitators Association 2020 conference, Dr. Acevedo performed a gross necropsy on a coyote (Canis latrans) and a great blue heron (Ardea herodias) in order to explore the causes of mortality as well as show the animals’ unique anatomical adaptations. The coyote was found deceased on the side of a road, likely hit by a vehicle. The male coyote had sustained blunt force trauma to the head causing a spinal dislocation and severe internal bleeding. The coyote also fractured its hind limb, but likely never felt the fracture due to the head trauma. The heron had been admitted to Portland Audubon after striking a large window. The bird died within the first 24 hours of being admitted to the wildlife hospital. The gross necropsy determined severe trauma to brain tissue. Further histopath of the heron’s brain tissue would be necessary to determine the exact cause of death.

Necropsies provide clues as to why wildlife are deceased or why they were admitted to a wildlife rehabilitation center in the first place. It is important that each facility have easy-to-follow protocols for necropsies so each one is performed in a consistent and systematic manner. Below are Think Wild’s protocols for both mammalian and avian necropsies:

Mammalian Necropsy Process:

1. External Exam

2. Incision at left armpits and left hip joints

3. Reflect abdominal and chest skin so abdomen and chest are exposed

   1. Look at abdominal contents in situ

   2. Poke through diaphragm to ensure you have negative pressure

4. Reflect ribs using rib cutters

5. Look at thoracic contents in situ

6. Remove abdominal contents (liver, upper and lower GI, spleen, pancreas, gallbladder)

   1. Cut where esophagus meets diaphragm and cut at end of rectum to remove entire abdominal contents except for kidneys

7. Remove pluck (trachea, esophagus, heart, lungs)

8. Remove kidneys and attempt to identify adrenal glands

9. Evaluate entire body

   1. Look for reproductive organs

-(Dr. Laura Acevedo, 2020)

Avian Necropsy Process

1. External Exam

2. Soak plumage in alcohol or soapy water

   1. This separates the feathers as well as prevents feathers from flying around

      1. Protects from risk of airborne infection

3. Place the bird in dorsal recumbency

4. Expose sciatic nerves on both R and L legs

5. Open coelomic cavity

6. Remove keel

   1. Cut through the superficial and deep pectoral muscles as well as the ribs on one side of the bird

   2. Incise pectoral muscles and ribs on the other side

   3. Disarticulate the shoulder joint or cut the ribs and the bones of the shoulder girdle, then remove the sternal plate

7. Inspect the coelomic cavity

   1. Inspect the thyroid glands near the heart base

   2. Examine the air sacs and viscera in situ, without touching them

   3. Examine the surface of the liver for changes in color, size, shape, or consistency

   4. Examine small and large intestines, spleen, and gallbladder

8. Examine the neck

   1. Remove the skin on the neck to expose the trachea, esophagus, crop, and thymus

   2. Examine the oropharynx, then cut along one lateral commissure of the mouth with scissors or an enterotome to expose the tongue, then take a closer look at the oropharynx

   3. Retract the tongue to expose the choana

   4. Bluntly dissect distally along the esophagus until the crop is separated from the subcutis

9. Evaluate Respiratory tree

10. Remove pluck and examine:

    1. Gastrointestinal tract

    2. Bursa of fabricius

    3. Cardiovascular system

    4. Adrenal glands

    5. Reproductive tract

    6. Kidneys

-(Lafeber, 2020)