Deer

White-tailed deer. (File photo/ Minnesota DNR)

ST. PAUL — Minnesota wildlife researchers have a thing for deer spleens this fall.

Starting this weekend with the state firearms hunting opener, researchers with the Department of Natural Resources are hoping to collect at least 800 of the organs from hunter-killed whitetail deer.

It’s part of a study to explore the levels of a widely used family of insecticides — neonicotinoids — in deer.

The study is the first step in getting at a heavy question: Are the controversial chemicals harming the state’s deer? Because it looks like they could be in the Dakotas.

The effort comes as neonicotinoids — the most widely used pesticides in the world and heavily used in Minnesota-grown corn and soybeans — face increasing scrutiny for their unintended effects on wildlife, from honeybees to birds to fish. Neonicotinoids are known to be toxic to pollinators and are among several likely culprits in bee population collapses.

Neonicotinoids are not known to cause ill health effects in people, and there’s been no evidence uncovered suggesting the state’s roughly half a million deer hunters should be concerned about feeding their harvested venison to their families because of pesticides. As for the state’s deer population, it’s generally been growing for several years, and hunting and harsh winters continue to be the largest factors in deer survival.

While the state’s efforts to manage the nascent-but-expanding chronic wasting disease among deer have occupied the minds of hunters and policymakers for more than a year, the concern over deer and “neonics” is new.

“There’s been a lot of research done on pollinators, so we know those effects,” said Eric Michel, the DNR’s farmland deer project leader who’s part of Minnesota’s new effort. “This is one step of us trying to be cutting edge and be on top of the game in managing the deer herd.”

South Dakota fawns suffered

Michel was a co-author of a recent study from South Dakota State University that grabbed the attention of wildlife officials around the country because it correlated higher levels of neonics with decreased baby deer, or fawn, survival, among other health problems.

The study, published in the journal Scientific Reports in March, found that deer that had higher levels of the insecticides in their bodies, notably the spleen, not only had lower fawn survival but also behavioral changes, such as feeding less often and being generally lethargic, and suffered from birth defects, such as a pronounced underbite, which could hurt their survival.

But more surprising to investigators was this: Even captive deer that hadn’t been given any neonics still had the stuff in their system, suggesting widespread contamination of the environment or food supply.

Are they everywhere?

The South Dakota study used captive deer. Researchers added imidacloprid, a type of neonic, to the water of some deer and none to others. The deer given the highest level had the highest level in their organs — and the lowest fawn survival. But the control group — the deer given normal water — also had neonics in their bodies. The stuff isn’t naturally occurring.

And there’s this: In wild deer in North Dakota, researchers found neonics at even higher levels than those that had been fed the chemicals in South Dakota. In some areas, such as the state’s badlands, the chemicals were found in deer where there’s little agriculture, raising the possibility that the chemicals are drifting over large distances.

What are neonics?

Neonicotinoids were developed in the 1990s and skyrocketed in popularity in the past decade. Because they work.

They’re proven to be highly effective at reducing crop loss from bugs, and because of the way the chemicals work, seeds can be coated with the insecticides before planting, and the resulting plants will have a level of protection. They are are also applied to plants via irrigation. The chemicals can drift away from farm fields in dust while planting, or when being applied separately.

In addition to commodity crops like corn and soybeans, neonics can be found on cauliflower, spinach, apples and a host of other produce people and wildlife eat.

They kill insects by disrupting their nervous systems. But bugs have different nervous systems than mammals or birds, so the idea was their impact would be limited.

Side effects

However, in addition to neonics’ toxic effects on beneficial bugs, such as honeybees, some studies have suggested that the ubiquitous use in some areas can have such a devastating effect on insect populations that birds and fish can suffer.

Direct impacts from eating neonic-laced crops is a new area of research.

Following its deer study, South Dakota State University is now embarking on a study to test levels in ring-necked pheasants, a popular game bird for hunting that is an important part of the state’s tourism economy this time of year.

 

Minnesota study

The goal of Minnesota’s study is to see how widespread the chemicals are in the state’s wild deer.

Michel, one of the researchers, says he suspects that deer that live in areas with more farms will have higher levels, although how high remains to be seen.

But what about deer in the far northeastern corner of the state, where little farming takes place?

“It wouldn’t surprise me if we find them there, too,” he said, noting the North Dakota findings.

Is it possible the chemicals are already causing health problems in Minnesota’s deer?

“Potentially,” he said. “But we won’t be able to say with this data.”

High interest

Last week, the DNR emailed hunters asking for volunteers to offer up spleen samples, as well as a tooth for aging the deer. The response was higher than expected, and Michel said officials are scrambling to assemble additional kits and had to stop accepting requests.

He said by this weekend, some 1,800 kits will have been mailed. Hunters that got their request in but have not received their kit this weekend can store the spleen in a plastic bag in the freezer while they await the sample kit.

The DNR has produced a short video showing hunters how to locate and remove the spleen, a hand-sized organ that is part of the immune system and looks similar to the liver but is smaller.

'21st-century DDT'?

 

The European Union has banned several neonics under certain circumstances. The United States and Canada have not, although a number of states restrict their use. Not Minnesota.

Several efforts led by Democrats to study or restrict neonicotinoids have failed to garner enough Republican support to succeed.

State Rep. Rick Hansen, DFL-South St. Paul, led a failed effort to mandate a study on their effects on deer specifically, much like the SDSU study.

Hansen said he commended the DNR for moving ahead with this study, and while Hansen hasn’t pushed for an outright ban on neonics, he said data increasingly show the need for stricter regulations on their use.

“They’re showing up in water; they’re showing up in soil. It’s the 21st-century DDT,” he said, referring to the insecticide that played a major role in the near-extinction of the bald eagle and peregrine falcon before being banned in 1972.

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