SteveM I didn't know that Cholecalciferol has been used in poisons of rodents, until I did the research yesterday. Luckily, there are no dogs or cats in my fenced yard or my general area, and the bait is always placed in a tunnel and covered. The Merck's Veterinary Manual discusses the acute dose(ingestion all at one time) and the median lethal dose(ingestion over time) all based on mg/kg of body weight. Math was always my best subject in school, but not having done math calculations in quite a while, it hurt my brain to figure out how many D3 pills would kill a 1/2 kilogram weight gopher. I calculated it would take 2 to 10 gels to kill a gopher in a 12-48 hour time frame. Also, the research study I referenced made it clear that follow up treatment is necessary in the coming months as new gopher populations come in ( there is a vacant piece of grassy land behind my yard).
