Abstract
Simple SummaryWe report here some of the major findings on the behavior of black bear mothers and cubs in their dens in the wild, based on observations in the state of Minnesota, USA. Wild female bears were outfitted with radio collars and their dens located as they prepared for hibernation in the fall. Cameras were installed in the dens and events in the den recorded until they and their cubs finally abandoned their dens in the spring. Although most reports of black bear cub behavior have been post den emergence, we provide intimate details of their birth, maternal behavior, and the development of the cubs from birth to emergence. Yearling cubs from the previous year sometimes remained with their mother for a second year. We discovered many aspects of mother, cub, and yearling behavior previously unknown and some of which contradict claims in the literature. Den cams are an important means of observing secretive behavior in settings previously impossible to observe unobtrusively.Denning behavior has long remained the least observed aspect of bear behavior. During 2010–2013, we used webcams, microphones, the internet, and 14,602 h of archived video to document the denning behaviors of two adult wild black bears (Ursus americanus) as they gave birth and cared for four litters through six winters in northeastern Minnesota. Observations included types of dens, labor, pre-parturient genital swelling, birthing positions, post-partum vocalizations, mothers removing amniotic tissues and warming newborn cubs in sub-freezing temperatures, frequency of nursing, cubs establishing nipple order, yearlings suckling, the ingestion of snow and icicles, the ingestion of foot pads, urination and defecation in latrine areas, toilet-licking, eye opening, reciprocal tongue-licking, play, rapid eye movement (REM) sleep and possible dreaming, and reactions to wildlife intruders. The use of this new method for observing natural bear dens allowed the identification of many behaviors undescribed for any species of wild bear in dens. We also discuss the need for future studies and how the depth and duration of black bear hibernation varies with body condition and geographic region.
Highlights
The behavior of bears in natural dens has long remained the least observed aspect of bear behavior.Prior to the invention of webcams in the 1990s, studies of denning behavior generally were limited to pre-denning and post-denning behaviors and the types of dens selected [1,2]
Animals 2020, 10, 1123 black bear (Ursus americanus) behaviors by visiting winter dens were hampered by observer effects and den abandonments [3,4,5,6,7,8,9,10,11]
Black bears in northeastern Minnesota typically produce their first litters at 3–8 years of age in January—the coldest month of the year [11,13]
Summary
The behavior of bears in natural dens has long remained the least observed aspect of bear behavior.Prior to the invention of webcams in the 1990s, studies of denning behavior generally were limited to pre-denning and post-denning behaviors and the types of dens selected [1,2]. Black bears in northeastern Minnesota typically produce their first litters at 3–8 years of age in January—the coldest month of the year [11,13]. Mothers care for their one to four cubs for 16–17 months until they mate again in May or June, giving birth every other January. Black bear cubs are nearly hairless and smaller, relative to the mother’s size, than other placental mammals [14] They average only 364 g at birth [15]) while mothers can weigh over 100 kg. Descriptive accounts of bear behavior are essential to ethological analysis and comparative behavior [17] and this work provides methods and incentives to carry out such studies on other species and populations
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