It is not surprising, therefore, that severe winters and changes in habitats cause marked sporadic declines in population levels through much of the currently occupied Canadian range. Deer in Canada are relatively free of serious diseases or parasites. In much of their range their natural predators, such as the timber wolf, coyote, bobcat, and mountain lion, have been greatly reduced in number and infrequently exert substantial pressure on the deer. Most of the predation on fawns occurs during the first few weeks of life. Free-roaming dogs do sometimes take a heavy toll on deer of all ages, particularly in late winter when crusted snow aids the dogs but hinders the weakened deer.
Deer reproduce quickly.
A healthy herd is capable of almost doubling its numbers during one favourable year. Under favourable conditions, female fawns tend to breed at 6-7 months and at 12 months of age produce singletons. Although a series of severe winters may tend to shrink the range of the white-tailed deer in Canada, a few favourable years permit it to reoccupy the lost ground, rebuild substantial populations, and even extend its range farther northward. Comparison of moose, rabbit, and white-tailed deer droppings. Management Maintaining healthy stocks of white-tailed deer is primarily a matter of keeping numbers of deer in balance with their supply of winter food.