In the mid 1980s blacktail deer in California’s Latour state forest were in decline. Investigations into the reasons for these declines suggested that selenium deficiencies were responsible for reduce fecundity. A study was conducted with selenium supplementation to determine if deficiencies in this trace element was responsible for the declines. Selenium boluses were given to deer that time released selenium into the deer’s system for long periods of time. The results of these supplementations was a 260% increase in fawn production. Several hypothesis were proposed for these selenium deficiencies including atmospheric deposition of pollutants, but none were explored.
Selenium and copper deficiencies have been observed in many of the Western wildlife declines that have marked the last 20-30 years, especially those of the last 20 years. These are probably due, at least in part to endocrine disruptions. They have been seen in elk in WA, sheep in WY, moose in UT, moose in MN, and almost everywhere in between.
Latour state forest is located at the East end of Shasta county, in Northern CA. California timber harvesters have utilized pesticides in timber harvests at increasing rates for decades, with a 26% increase in pesticide use in Shasta county alone.
The lower elevation wintering areas of Latour also have several large power line right of ways, and pipeline right of ways adjacent to, and running through the forest. Many, if not most of these are herbicide treated.