The organization applied the pesticide to two of its four herds, believing that permanent sterility would not occur until seven years of repeated use.
Mares in the Catnip herd (from Sheldon NWR) became infertile after five years.
Application to the Virginia Range herd was stopped at four years.
Four years later, nine out of approximately 36 Virginia Range mares began to cycle again and have foals.
Of those, seven did not survive.
Six died within the first day of birth while a colt died at six months.
He appeared to be a “failure to thrive” foal; thin, retaining a heavy thick coat in the heat of the summer, and suffered from malaise.
On one occasion, a filly was accidentally darted and was observed for several years.
She never became pregnant, while her untreated cohorts were able to get pregnant.
All conditions were the same regarding hay, water and space. The only difference was her inoculation with PZP.
These and other such cases, such as the disaster on the Maryland side of Assateague Island, where the herd is still shrinking eight years after the darting program was shut off, give you a method for judging the sincerity and veracity of the wild horse advocates.
Most will fail the test.
Studies of the four herds ended in 2016 with the ISPMB collapse.
Adapted from the discussion at the bottom of page 41 in this report.
RELATED: Assessing the Risk of Sterility in PZP Darting Programs.
Western Horse Watchers Association 