Date of Award
Level of Access Assigned by Author
Master of Science (MS)
Wildlife Ecology and Wildlife Conservation
Shawn T. McKinney
Second Committee Member
Daniel W. Linden
Third Committee Member
Mary S. Tyler
The American black bear (Ursus americanus) relies upon dens in order to successfully reproduce and protect their offspring. Black bears utilize a variety of den types, each providing a different degree of protection. Black bears also exhibit an extended maternal care period in which offspring stay with their mother for 18 months. Maine’s black bear population is one of the largest in the U.S. (>30,000 bears) and since 1975, the Maine Department of Inland Fisheries and Wildlife has conducted research and monitoring to manage the population. This unique dataset allowed for examination of several generations of multiple maternal lineages which was ideal for assessing both den type selection and primiparity (age of first reproduction).
My objectives for this study were to determine 1) whether subadult females chose the same den type as their mother (maternal effect) or if they selected a den near their yearling den, regardless of den type (philopatric effect); 2) whether differences among study areas explained observed differences in den site selection, 3) if there was regional variation in the age of primiparity of Maine black bears; 4) the relationship between the age of primiparity and the probability of recruitment from the primiparous litter; 5) the relationship between the age of primiparity and lifetime productivity; and 6) the relationship between the age of primiparity and body condition.
I analyzed den selection data of 168 subadult females and primiparity data of 85 females from 1981-2013 at four study sites in Maine using GIS, generalized linear modeling, model selection, and analysis of variance (ANOVA). The top den selection model, which included maternal effect and study area, accounted for 85% of the den type selection model likelihood. Maternal effect models were more strongly supported than philopatric effect models and regional variation in den type use was observed. These results suggest that not only is a behavioral maternal effect present in black bears and that this maternal effect combined with regional variation in den type availability influences den type selection, but also that the protection afforded by den type may be an important factor in selection decisions.
I found regional variation in age of primiparity among the study areas (p = <0.001). Multiple comparison testing indicated age of primiparity differences between Spectacle Pond – Bradford (p = <0.001) and Stacyville – Bradford (p = 0.009). Logistic regression indicated there was a difference in the successful recruitment of at least one offspring from the primiparous den among the primiparous ages (p = 0.002). Probability of successful recruitment increased with increasing age of primiparity. I found no difference in lifetime productivity among the primiparous ages (p = 0.532). I also found no difference in primiparous body condition among the primiparous ages (p = 0.591). These results suggest that regional differences in food quality and abundance may influence regional variation in age of primiparity. Understanding factors that influence den type selection as well as the influence of age of primiparity on other reproductive life history traits can help guide wildlife and habitat management decisions.
Vitale, Alyssa A., "Reproductive Ecology of Black Bears in Maine: Maternal Effect, Philopatry, and Primiparity" (2015). Electronic Theses and Dissertations. 2305.