White tail deer must be killed, we have broken their habitat.
Over the last 400 years Millions of acres of Forrest have been converted to planes and farmland, and most of the large North American predators have been killed.
So instead of deer having to forrage in Forrest they can be eat more effectively by grazing, and without natural predators like wolves the deer population can grow unchecked. Deer will reproduce until the area can’t support the population leading to starvation. Also the deer population has let them spread to new areas where they can out compeat animals like moose, elk, and caraboo, causing the larger animals population to plummet.