Excerpt from and article concerning the Eastern coyote:
In Nova Scotia we have the luxury of looking to other areas with coyotes and deer to see the impact on herds there. Invariably, biologists from these jurisdictions tell us that coyotes by themselves have little or no effect on the number of deer. In fact may of these areas are trying to reduce deer populations to bring them ore in line with the ability of the habitat to support them. For example, New York state first recorded coyotes in the 1930s and had a well established population by the 1960s. Despite a healthy population of coyotes, New York's deer population hit an all time high during the 1980s.
Although coyotes can and do kill healthy adult der, they are more likely to catch animals which are young or in poor physical condition. In many cases these animals would have died form other causes even if not killed by coyotes. this helps to explain why coyotes have not been observed to control deer populations. Additionally, coyotes place controls on their own populations by establishing exclusive breeding territories where only one coyote pair breeds in a territory. Territory size is somewhat regulated by the availability of food. In Maine, these territories average about 50 square kilometers (20 square miles).