Are Toxic Agrichemicals Forcing Rapid Evolution in Yellowstone Elk?

CORRECTION: The article below incorrectly referred to elk calf research conducted in the Jackson, Wyoming area by biologist Doug Smith. We’ve corrected the piece to indicate the research was conducted by biologist Bruce L. Smith.

by Laura Lundquist

In the spring of 1995, Bob and Judy Hoy began to see disturbing trends in the animals around their Stevensville home south of Missoula, Montana.

“I noticed things were dying that shouldn’t be dying,” Judy said in a May 2022 interview. “Baby marmots just disappeared. All of the toads in our yard just disappeared. Then people in the neighborhood who had livestock, their livestock were born with very short upper faces, causing them to have underbites.”

The Hoys both had biology backgrounds—Bob was a game warden with Montana Fish, Wildlife and Parks and Judy was a biology teacher and wildlife rehabilitator—so they started piecing events together. Their suspicions increased a year later when Bob picked up several road-killed whitetail deer and eight out of nine yearling bucks had malformed reproductive organs. Some deer also had underbites due to shortened noses, the same as the livestock.

For the next 20 years, the Hoys tracked similar deformities and reproductive problems in Montana’s wildlife from the Bitterroot Valley into the Greater Yellowstone Ecosystem. Bison calves were found with shortened noses and some bulls had noticeably short scrotums. Elk calves were smaller and developed slower. The deformities seem to fit a pattern of teratogenesis, where deformities and deaths are caused by chemicals or viruses that damage an organism’s development. Thalidomide, for example, is a teratogen that pregnant women took for nausea in the mid-20th century, but which was later found to inhibit limb growth in their children.

Even back in the 1990s, Hoy suspected the wildlife deformities were related to the increased use of agrichemicals—chemicals used to eliminate herbivorous insects, fungi and weeds to maximize crop harvests—in the fields of Montana and surrounding states.

Now, Judy and two other researchers have published a review paper that pieces together her observations and similar wildlife problems documented in Montana during that 20-30-year span. They then present recent research suggesting the problems could be connected to a surge in the use of hazardous chemicals used in farming that was documented at the same time. Their review paper was published last month in the May issue of the peer-reviewed scientific journal Chemosphere.

“The paper is primarily concerning the Greater Yellowstone Ecosystem and effects of teratogenic toxins on the wildlife there and in surrounding states, especially Montana and Wyoming,” Judy Hoy wrote in a May 22, 2024 email to Mountain Journal. “The general public needs to know about the serious effects that are happening to vertebrates, especially mammals, since humans are mammals.”

Even back in the 1990s, Hoy suspected the deformities were related to the increased use of agrichemicals—also called agrochemicals—used to eliminate herbivorous insects, fungi and weeds to maximize crop harvests in the fields of Montana and surrounding states. Her suspicions were reinforced when she learned that a 1991-1992 University of Montana study of whitetail deer on the Lee Metcalf National Wildlife Refuge near Stevensville found no defects.

The Hoys reported their findings to Montana Fish, Wildlife and Parks in the mid-‘90s, but Judy says they weren’t taken seriously. In 1999, however, the U.S. Fish and Wildlife Service at the Lee Metcalf Refuge created a six-member study group of veterinarians and biologists to determine whether pesticides were responsible for the wildlife anomalies.

While verifying that Hoy’s wildlife observations were real, the group report said they were unable to make any pesticide connection. The study group was “distressed” to learn they couldn’t find any information on pesticide application in Ravalli County due to the minimal data the state gathered at the time. Congress

had passed the Food Quality Protection Act only a few years earlier mandating pesticides be assessed for their ability to disrupt the endocrine or hormone system. The screening and testing methods for endocrine disruption are still being developed.

“While the implication of pesticide exposures and disruption in calcium-signaling are intriguing, we simply could not find enough hard evidence to confirm this conclusion,” the group concluded, adding that further investigation was justified.

The U.S. Fish and Wildlife Service didn’t follow up. But in the 25 years since the report, other researchers have. Hoy and two other researchers cite dozens of those studies in their review to build a picture of how a documented surge in the use of agrichemicals in the 1990s could have affected elk, deer and other ruminants in southwestern Montana and Yellowstone National Park to the point that it contributed to population declines.

Some have blamed the decline of elk populations in Yellowstone, particularly the Northern Herd, on wolves, which were reintroduced in 1995-96. After all, the review paper cites, “between 1994 and 1997–98, the winter counts of the population of northern Yellowstone elk declined by

one third [and] the 2013 winter counts indicated declines of more than 75 percent over two decades.”

But the paper points out that new wolf packs living in the park could not have eaten enough to account for the population loss of about 10,000 elk between 1994 and 2004. The average of 130 wolves that tend to inhabit the park would have each had to eat 20-22 elk annually, which is highly unlikely since they also eat other animals. A range of carnivores eat elk, but the review found that “most scientific investigations concluded that unknown or unexplained factors were likely involved.”

The review cites elk research that former Yellowstone biologist and wildlife manager Bruce L. Smith carried out near Jackson Hole, Wyoming. Elk calves captured in 1990, 1991 and 1992 were healthy enough to join the herd after about 12 days and none were killed by predators after that. However, when the same research was carried out in 1997, 1998 and 1999, the calves, especially females, were smaller and grew slower, so they suffered four times more predation than calves from the early study. Other studies in the park found cow-calf ratios of 30-40 calves per 100 cows dropped after 1994 to less than 20 calves per 100 cows. Aside from predation, the causes of death in the later calves included heart defects or difficult births.

What caused elk calves born in the late 1990s to fail to thrive compared with those in the earlier study? Similarly, what caused whitetail deer in the Bitterroot Valley to develop deformities after 1995 and prompted a rise in reports around the same time of domestic animals born with malformations and health issues? Hoy and her colleagues note that “the second study period occurred following the massive increases in regional use of teratogenic agrichemicals.”

The review details how the use of three kinds of agrichemicals—now recognized as teratogens—surged in the crop fields of Washington, Oregon, Idaho, Montana and the Dakotas between 1994 and 1996 and describes how the animals who browse or live in vegetation sprayed or indirectly contaminated by such chemicals could have been harmed.

In 1994, a regional outbreak of blight led to a 10-fold increase in the use of chlorothalonil fungicides in the potato fields of Washington, Oregon and Idaho. Unintended spray drift and deposition of chlorothalonil in rain and snow has been shown to contaminate plants and surface waters across extensive areas. Such fungicides contain cyanide and are most toxic when inhaled. Studies show laboratory animals exposed to chlorothalonil suffered embryo loss, kidney and liver damage and chromosome aberration.

“Damage to the liver and kidneys can interfere with an exposed animal’s ability to detoxify and excrete other toxins to which it is exposed,” according to the review. “Thus, synergy with other pesticides in the environment likely results in greater injury to the internal organs.”

There were plenty of other pesticides. Also in 1994, people started spraying a newly registered neonicotinoid insecticide called imidacloprid in Oregon, Washington and Idaho. Plants take up the synthetic nicotine, which damages the nervous systems of insects that eat the plants. However, neonicotinoid insecticides are also implicated in the decline of several species that pollinate flowers, such as the western bumble bee.

The paper points out that new wolf packs living in the Yellowstone National Park could not have eaten enough elk to account for the population loss of about 10,000 elk between 1994 and 2004.

But in vertebrates, imidacloprid is an endocrine disruptor, acting on the hormone system. In 2015, a South Dakota State University researcher gave varying amounts of imidacloprid to captive whitetail does and found the does that received the chemical had offspring with underbites and malformed reproductive organs. And the higher the amount of imidacloprid, the worse the deformities and fawn survival.

Finally, in 1996, the introduction of Roundup Ready crops—those that are resistant to the Monsanto-produced herbicide Roundup—resulted in farmers using even greater amounts of glyphosate-based herbicides or GBH. GBH reduces plant uptake of essential minerals such as manganese, which means herbivores can suffer mineral deficiencies that impair their metabolism. In addition, studies have found that direct exposure to GBH can cause major reproductive problems, including preventing pregnancy or producing offspring that are stillborn or have abnormalities. Another study cited in the review found problems associated with GBH exposure can be expressed in offspring two or three generations later.

The review claims that GBH exposure alone could explain the decline in the Yellowstone elk populations and the low cow-calf ratios Smith found in the Jackson area. But the combination of all three agrichemicals that surrounded southwest Montana could have interacted in varying amounts to worsen the effects on animals. Studies have shown that organisms downwind of treated fields can be exposed to toxic mixtures of pesticides.

However, even though the use of agrichemicals hasn’t diminished, the review authors noted that the Yellowstone elk population started to recover after 2014, although cow-calf ratios are still low. They’ve also seen far fewer ruminants with birth defects since 2014, but they’ve observed that the sex ratio has skewed more toward females. They suggest that this could be the result of rapid natural selection in response to the agrichemicals. Females more susceptible to the chemicals died or failed to reproduce while more resistant females prospered. In short, if agrichemicals did play a role, Yellowstone elk and other ruminants could have adapted over a few generations to better withstand the worst effects of the substances.

The need to investigate the dangers of toxic agrichemicals, however, remains. The authors write that “even if selection occurs in wildlife for genotypes most resistant to endocrine disruption, the effects of ubiquitous teratogens on the health of domestic ruminants and other animals, including humans, will likely continue and possibly accelerate.”

Coauthor Pamela Hallock Muller, University of Southern Florida oceanographer and Hoy’s sister, said some of the research they cited has only recently been published because scientists have been sometimes discouraged from delving into the hazards of agrichemicals. And money for such research isn’t provided. So, people who suspect that harm is occurring have a hard time getting the public to pay attention to potential problems.

“The endocrine disruptors are something I’ve been interested in, partly because I’m female and I was born at a time when people used DDT,” Muller said in a recent interview with Mountain Journal. “My mother thought insects were bad and DDT was good. We grew up on a dairy farm and put malathion on our cows before we milked them. It’s equivalent to the smoking issue in that there’s too much economic interest in the use of these chemicals.”

DDT was banned in 1972 due to its persistent toxicity and its effects on human and animal reproduction. The insecticide malathion, which attacks insects’ nervous systems like neonicotinoids, is still being used although environmental advocates, including the Center for Biological Diversity, have repeatedly sued the Environmental Protection Agency for two decades to get it to consult with the Fish and Wildlife Service about the effects on wildlife. The history of the lawsuits backs up Muller’s description of the difficulties in documenting and regulating industrial chemicals.

“The general public needs to know about the serious effects that are happening to vertebrates, especially mammals, since humans are mammals.” – Chemosphere

Judy Hoy, researcher, coauthor, Teratogenic Agrichemicals,

In January 2017, the EPA determined in a biological evaluation that 97 percent of federally protected species are likely harmed by malathion. But under the Trump administration and at the request of the manufacturer Dow Chemicals, the EPA and Fish and Wildlife Service indefinitely suspended the malathion assessment.

The Center for Biological Diversity sued again but the Biden administration agreed to resume the assessment. A 2021 U.S. Fish and Wildlife Service draft biological opinion determined that malathion jeopardized 78 listed species. But the following year, the agency walked back its draft finding after chemical manufacturers pledged to change product labels to better inform consumers. This April, the EPA issued guidance on the labels.

The Center for Biological Diversity has the financial resources to force agencies to investigate chemical hazards. Hoy and her coauthors don’t. They’ve tried to gather the data and draw the connections themselves. But since Hoy is in her 80s, this review is likely her swan song.

“I’m making one last gasp trying to get these critters saved before it’s too late,” Hoy said. “Neonicotinoids and glyphosate work together, causing everything to die 1,000 times faster.”

EDITOR’S NOTE: Drugwatch, a consumer advocacy organization reached out to MoJo with two guides to glyphosate, the active ingredient in Roundup. By providing professional information, backed by science and healthcare professionals, and backed up in peer-reviewed scientific journals, Drugwatch is aiming to look out for consumers. It has received an “A+” rating by the Better Business Bureau and has been featured in The New York Times, The Hill, and Huffington Post among other trusted publications.

Learn more about glyphosate in Drugwatch’s guides here, and more about Roundup here.

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