Lead poisoning and wildlife
In Canada the use of lead ammunition for waterfowl hunting has been prohibited since 1999.
Despite the ban we are unfortunately still encountering waterfowl with lead poisoning. Particularly swans who use their bill and long neck to rummage through the sediment still ingest lead pellets historically present at popular hunting locations.
We also encounter waterfowl from south of the Canadian border with lead poisoning. These birds have been shot non-lethally with a lead pellet as collateral damage during waterfowl hunting to fall ill with lead poisoning after arriving in Canadian waters.
What is not as obvious as these cases is the countless scavenging wildlife that succumb to lead fragments ingested from consuming waterfowl or small game who have succumbed to lead poisoning or hunter-left gut piles during (small)-game hunting.
The ammunition used in deer hunting traditionally is lead based and is made to expand on impact. Hunters generally aim for centre mass meaning that the bulk of the lead fragments will be in amongst the organs and thus in the gut pile left after field dressing a deer.
These gut piles are favoured by a variety of wildlife. Bald Eagles are notorious scavengers and many of them experience a negative health impact associated with the lead hidden in the gut piles. A study done in 2018 by Martin et al found that 23% (10/43) of eagles found dead and dying in Ontario between 1991 and 2008 died of lead poisoning. This study did not look at the long term effects of periodic lead poisoning on the overall longevity of eagles.
If the level of lead is non-lethal with the ingested portion passed through the digestive tract and the lead absorbed in the blood stream filtered out by the liver/kidneys prior to acute serious clinical symptoms occurring the animal’s overall longevity will be negatively impacted. This negative longevity impact needs to be considered as well.
All scavenging wildlife is effected by lead poisoning. This includes various species of bears, coyote’s, wolves, eagles, vultures, ravens, crows and smaller mammalian scavengers like wolverine’s, martens, fishers and mink.
Symptoms of lead poisoning
The main clinical symptoms of lead poisoning we see are lethargy, progressive weakness, green-stained feces and cloaca, inability or reluctance to fly/stand, weight loss, and emaciation.
In eagles who are more sensitive to lead poisoning we also see neurological symptoms such as paralysis of the legs, difficulty swallowing, poor head control and general weakness.
Lead poisoning can be confirmed through blood testing and radiology.
Treatment
Aside from removal of lead source lead chelation therapy is used. The chelating agent (most often calcium ethylenediamine-tetraacetic acid) binds the lead in the blood stream and when the CaEDTA is removed from the body by the kidneys the lead leaves with it.
For many wildlife patients this treatment is too little too late and of those who survive many will have permanent neurological/organ damage, but those who recover make the effort worthwhile.
Human Health Risk
Aside from the negative impact of lead on wildlife and the environment it also has a very direct impact on humans who eat the meat from game shot with lead based ammunition. A research study done into the lead fragment presence of rifle killed white tailed deer showed lead fragment present in a high proportion (80%) of deer showing at least one bullet fragment in one or more ground meat packages.
Prevention
Lead sources present in the environment cause long term wide spread damage.
With lead free alternatives readily available many conscientious hunters and anglers have already made the switch to copper and steel based options.
Increased demand has brought the prices of copper based ammunition down to a comparable level with premium lead based ammunition. Thus far research has shown no negative environmental impact of copper based ammunition and the non-lead based bullets preform just as effective as traditional lead based bullets in ballistics testing.
Additionally people can help by properly disposing of their car batteries, lead based paint and old fishing and hunting gear. Every municipality has special days every year where you can drop off these environmentally sensitive items free of charge.
While we as wildlife custodian continue to grapple with lead poisoning cases we sincerely encourage hunters and anglers to take a proactive approach and make the change voluntary rather than waiting for legislation.