Causes of Eagle Mortality in Saskatchewan
Every year, bald eagles and golden eagles are regularly submitted to the Canadian Wildlife Health Cooperative (CWHC) Western Northern Region for post-mortem examination. As part of a Masters of Veterinary Science Special Topics course in 2013, Steven Scott (now a veterinary pathologist at CWHC Western/Northern) summarized the causes of mortality in eagles in Saskatchewan over a 21-year period.
This retrospective study recently published in Canadian Wildlife Biology and Management confirmed that human activity contributes to a significant number of eagle mortalities in the province. Poisoning was the most common cause of death in bald eagles, while poisoning and trauma were equally common in golden eagles. The majority of these poisoning cases were attributed to organophosphate/carbamate insecticides, followed by lead toxicity. Eagles are more susceptible to poisoning because they readily scavenge on carrion (dead animal carcasses).
In Saskatchewan, organophosphate and carbamate insecticides are often used by individuals to illegally poison wildlife (e.g. coyotes) that they consider a nuisance or threat to their livestock. These poisons are frequently placed on bait (usually the carcass of larger animal), and once consumed they affect the nervous system and cause death by respiratory muscle paralysis. Eagles are more often secondarily poisoned after they scavenge on the animal that has already consumed the insecticide.
Lead poisoning typically occurs when eagles consume the flesh of another animal that contains lead-shot, or less commonly lead-sinkers. Public outreach programs to increase awareness regarding illegal poisoning and banning the use of lead-shot on upland game birds and mammals may help mitigate these problems.
For more information on causes of death in Saskatchewan eagles, see Scott, S. J. and T. K. Bollinger. 2015. The causes of eagle mortality in Saskatchewan, 1992-2012. Canadian Wildlife Biology and Management 4(1) 31-39.
Submitted by Steven Scott, CWHC Western/Northern