Mule deer at the Hanford site in Washington have experienced declines, and high rates of testicular atrophy since the early 1990s. The affected deer had retained velvet and did not shed their antlers annually. These are commonly known as “cactus bucks”. Information about studies of these deer can be found here:  and here:

These deer showed low copper and thyroxine levels compared to other sampled deer. Copper deficiencies have been associated with wildlife declines across the West since the early 1990s. Copper deficiencies have been seen in Hoof rot in Washington elk, and moose declines in Minnesota. Declining moose populations in Utah have shown copper deficiencies, and also exhibit hoof abnormalities. Declining Antelope in Arizona, Oregon, and Idaho, have also been shown to be copper deficient in the last 20 years. Deer in Utah have also been shown to preferentially select for copper in feed. Thyroxine is a thyroid hormone that is closely related to selenium in the thyroid Thyroxine also known as T4 is converted to the hormone T3 in the thyroid. Selenium deficiencies have been associated with wildlife declines and malformations across the West. These selenium deficiencies have been documented in Washington elk, Utah moose, Wyoming bighorn sheep, Alaska moose, Minnesota moose, and California black tail deer. Additionally mule deer in Utah have been shown to feed preferential for sage brush higher in selenium content.

Deer in other studies that have exhibited cryptorchidism (undescended testicles) and testicular atrophy have been shown to be born with this, rather than acquiring it later in life. This would suggest that disruption of the hypothalamic-pituitary-gonadal (HPG) axis during gestation, and specifically at the masculinization window, may be where this begins. Cyryptorchidism and testicular atrophy have been shown to occur sympatrically with other malformations such as under bites, which have also been shown to be associated with thyroid disruption. Disruption of the thyroid, part of the hypothalamic-pituitary-gonadal (HPG) axis, is typically caused by chemical action, such as pesticides, specifically 2,4-D

Since the early 1980s the Hanford site has used over “50 compounds to control vegetation in and around operational units and roads, primarily to prevent wildlife intrusion into radiological contaminated areas” In 1995 and 1996 the brain tissue of five Hanford site deer were tested for the presence of pesticides, one was found to have both 4,4′-DDE and Endosulfan sulfate present. 4,4′-DDE and Endosulfan sulfate have both been shown to increase the rates of cryptorchidism. The pesticide Sulfometuron Methyl, known by the trade name “Oust” has been used extensively on the Hanford site. Sulfometuron Methyl has been shown to produce testicular degeneration and atrophy. Sulfurometuron Methyl is a Sulfonyurea herbicide similar to Metasulfuron-methyl that has been used on the National Bison Refuge in MT and at Malhuer National Wildlife refuge in OR.

At the same time in the early 1990s, that testicular atrophy was observed in mule deer, there were large scale sagebrush die offs occurring on the site, that continued to spread. The testicular atrophy ebbed and flowed for many years, with the number of affected deer increasing since 2007. This same increase in wildlife malformations has been seen in other areas such as the Bitterroot Valley of MT, the Lander area of Wyoming, and across the West. The use of herbicides by the BLM has increased with their revised 2007 pesticide application plan, which triples the acres to be treated annually from ~300,000 to ~900,000, adds four new herbicides, and expands the program from 14 to 17 Western states. Previous BLM pesticide use plans coincide with previous wildlife declines of the early ’80s, ’90s, and 2000s. The use of insecticides in the West has also increased since 2006.

See: Sulfonylureas