While Rocky Mountain elk have thrived across most of the West, Lolo zone elk in Idaho have been declining for 20 years. This area is just over the mountain from Montana’s Bitterroot Valley, and Thompson Falls MT where large numbers of wildlife have declined for 20 years. The Lolo and Selway areas hold some of the highest concentration of Idaho’s clear cuts. Herbicide use in timber harvest has been increasing for decades. Elk in timber harvest areas, like the Bitterroot Valley, WA and OR have been suffering declines and malformations, while most elk have thrived outside of these areas.

Studies have shown that these declining elk have lower selenium levels, and pregnancy rates, compared to other areas. It has been shown that cow elk in these declining herds have low progesterone levels.  It has been proposed that these low progesterone levels are a result of Predators. “The predation stress hypothesis suggests that exposure to predators causes elevation of glucocorticoid (GC) stress hormones (10, 1618), which can directly suppress reproduction through effects on the hypothalamic-pituitary-gonadal axis (19, 20), and can indirectly reduce survival and reproduction through effects on the immune and digestive systems”

While the predator hypothesis has not panned out, it has been shown that endocrine disrupting herbicides can achieve exactly what has been proposed to be caused by predators. 60% of all pesticides are endocrine disruptors, that affect the  hypothalamic-pituitary-gonadal axis.

Progesterone and estrogen balance each other in the body. When estrogen is increased progesterone is decreased. This can also happen when estrogen mimics like many pesticides trick the body into thinking that estrogen levels have risen, this in turn causes progesterone to decline.

Elevated glucocorticoid levels, could be the result of sulfonylurea induced hypoglycemia.  Sulfonylureas induce hypoglycemia by acting on the pancreas, when hypoglycemia is induced, cortisol(glucocorticoid hormone) is released, in an attempt to reverse the hypoglycemic state. 

Much of the timber harvest in the Lolo zone is conducted on Potlatch property. Potltatch corp uses herbicides in its timber harvests, like most timber companies over the last 30 years.

Besides timber harvest there is the issue of weed control. ” When the U.S. Forest Service (USFS) stopped spraying herbicides in the Lolo National Forest during the 1980’s, it did not adequately address the potential spread of invasive weeds with an alterna- tive approach. During this time, invasive weeds took hold and began to spread through the Lolo Forest. Reacting after years of a “do nothing” approach, USFS reintroduced herbicides into the Lolo National Forest for the first time in 1992, as part of its weed management program. ”