Hunters may minimize lead exposure to wildlife, especially such scavengers as golden eagles that feed on carrion, through choosing proper types of ammunition, a new study noted.

"Choosing an ammunition type, such as .22-caliber solid bullets, that creates substantially fewer fragments can be a way to minimize lead exposure to scavengers and other wildlife," said Collin Eagles-Smith, co-author of a study on links between ammo used by hunters and lead exposure to wildlife.

Some pests "are really an economic threat to farmers, and shooting them is one method to control their numbers," said Ealges-Smith, an ecologist from the U.S. Geological Survey (USGS) and a courtesy assistant professor of fisheries and wildlife at Oregon State University (OSU).

"Picking up every last carcass is not realistic, but there are choices people can make regarding ammunition that may result in smaller amounts of lead in the carcasses left behind," the researcher was quoted as saying in a news release from the OSU this week.

The study was conducted by a team of researchers who used a new bullet-fragment recovery technique known as "digestion" to look at how much lead remained in the 127 ground squirrel carcasses from alfalfa fields in southern Oregon and northern California and how that is correlated with the type of bullets used.

Eleven western U.S. states produce roughly 40 percent of alfalfa in the United States, and burrowing mammals such as ground squirrels and prairie dogs can cause significant yield loss.

Shooting the rodents is an important form of pest control as well as a popular recreational pastime throughout the West.

The carcasses are typically left in the fields, where avian scavengers like eagles, hawks and kestrels descend upon the carrion to feed both themselves and their nestlings.

In their study, published in the U.S. journal PLOS ONE, the researchers, including USGS scientists, estimated the amount of lead left in a carcass and the potential effect of the lead on nestlings' mortality, growth and digestion.

The research found 80 percent of shot carcasses had detectible fragments of lead.

Squirrels shot with high-velocity, high-mass .17-caliber Super Mag bullets, for example, had 28 times the retained fragment mass of those shot with .22-caliber solid bullets.

It noted that hawk and eagle nestlings fed regularly with shot ground squirrels could likely lose more than half the production of the key enzyme ALAD throughout the nestling period, though no nestlings would be expected to die of lead poisoning. But their later growth could be impaired. it added.

source: Xinhua