Purpose of Necropsy

September 7, 2023

Question: What determines when or why CDFW performs a necropsy?

Answer: CDFW routinely conducts statewide mortality and disease investigations on fish and wildlife. One of the first steps when conducting mortality investigations is a necropsy, which is a thorough examination of animal remains, similar to an autopsy. The purpose of the necropsy is to determine why an animal may have died and it can inform scientists about health threats to wildlife populations due to diseases, toxins, injuries or other conditions. The reason an animal may have died could have larger effects on the entire population and could prevent recovery efforts for threatened and endangered species. Understanding threats to wildlife health is also important for monitoring domestic animal and human health, as some diseases or health risks can be transmitted among species (e.g., rabies, plague).

Necropsies can also help provide information on common causes of death and background mortality rates, which are useful for detecting unusual mortality events that may be attributed to disease epidemics or the emergence of new diseases and their geographic spread (e.g., West Nile Virus, White Nose Syndrome, and SARS-Cov-2).

CDFW wildlife officers may also request a necropsy to assist with a law enforcement investigation. For example, a necropsy can determine if an animal died naturally, or was instead shot or poisoned.

Finally, the necropsy of a dead animal during a disease outbreak or toxic event can save the life of a sick animal by guiding important treatment decisions.

A couple of weeks ago I saw a F&G biologist collect two yellow eyes for necropsy.  Easy to determine the cause of their demise, hook in the mouth disease.  Fortunately for the two fishermen that collected the samples, the biologist did not have law enforcement ability so they gladly surrendered their catch for study.