Organizers of a whitetail birth control program in Hastings-on-Hudson, NY, admit the effort is off to a slow start, citing heavy snow, regulations, and “the unpredictability of the animals.” Workers from the Humane Society of the United States had hoped to catch 40 to 50 does and inject them with a birth control drug, but they have only caught eight after a month, The Associated Press reports.

The contraceptive program, designed by Allen Rutberg, director of the Center for Animals and Public Policy at Tufts University, is said to be the first attempt to control a free-roaming deer population in a suburban area. “Free roaming” is the key word, unfortunately for the HSUS workers trying to capture deer. Heavy snow in the park the deer ordinarily call home drove the animals into the shelter of back yards, forcing workers to go door to door asking permission to capture deer.

While the vast majority of homeowners granted access to their yards, workers only managed to catch and inject eight does — seven in the final week. They will try again next year.

“They know there’s no alternative for us,” said Mayor Peter Swiderski. “You can’t walk around on quarter-acre zoning with a crossbow.”