Cooperative Fish and Wildlife Research Units Program: Maine
Education, Research and Technical Assistance for Managing Our Natural Resources

The Maine Department of Inland Fisheries and Wildlife (IFW) has been conducting a black bear (Ursus americanus) monitoring program for the past 39 years in order to manage the population effectively, primarily through hunting regulations. Female black bears require a den to give birth and protect their offspring during early development, and these dens provide both thermal and security cover. Maine black bears utilize a variety of den types, each providing a different degree of protection. Tree dens are the most protective den type, while ground nests are the least protective. Currently, it is not well understood whether there is a relationship between the level of den type protection and recruitment rates. The age of primiparity is defined as the age at which a female first reproduces. In Maine, first litters historically had lower cub survival rates than subsequent litters. The size and condition of black bears are closely linked to their diet, specifically the amount of high fat and high carbohydrate foods consumed. The size and condition of adult female black bears can influence their reproductive performance and determine their age of primiparity. As a result of this connection, variation in the age of primiparity is likely linked to the availability of food resources. However, we do not know how age of primiparity affects individual lifetime reproductive performance, and therefore, population recruitment. The objectives of this study are to: (1) examine den type use to determine if den type affects Maine black bear recruitment, and (2) examine the regional variation in age of primiparity of Maine black bears to determine how the age of primiparity affects recruitment.