In most years, energy-rich berries are plentiful during the autumn season. Berry crops are critical to northern bears which must survive with a narrow variety of foods and a short foraging season. When berry crops fail as they do every few years, black bears are forced to travel widely in search of food. Their desperation brings them into greater contact with people during these times. Berry crop failures can also affect the reproduction of black bears.
Pregnant bears go through a process known as delayed implantation.
This means that the embryo lies dormant in the uterus for several months, and does not begin to develop until November or December. During a bad berry year, if the female is in poor condition the embryos will not implant and no cubs will be born. This probably saves the mother's life. In October, when the temperature drops and the snow flies, black bears search for new den sites and the cycle begins once more. The black bear's inquisitive and adaptable nature has led it into contact with humans and their campsites for thousands of years.