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The habitat that an
organism lives in depends on several different
components, such as: diet, predators, and
shelter within that habitat. As different as
these aspects all are, they all have one thing
in common, they are necessary survival
components for an organism.
Ursus americanus,
more commonly known as the American black bear,
abides by these guidelines with regards to the
habitats and regions in which it typically
resides (e.g. Rogers
et al.,
1988). The typical habitat of a black bear is secluded solely to the North American continent (Goodrich and Berger, 1993; Pelton, 2003; Fairies, 2013). However, this is fairly large expanse of land, and although it is a common belief that bears only live in cold forests, bears have been found inhabiting regions as far south as Florida (Kennedy et al., 2002; Garrison et al., 2012) to as far north as upper portions of Canada (Oftedal et al., 1992; Brito et al., 2010). They are a diverse enough creature that they can live in both warm climates as well as the harsh cold ones found in northern Canada (Bartareau et al., 2012). Black bears tend to navigate towards regions that have a freshwater supply close, like a river or a marsh (e.g. Sadeghpour and Ginnett, 2011) with low-to-the-ground vegetation like shrubs (e.g. Pelton et al., 1999). These are all common elements which are prominent in a deciduous forest or boreal forest, they usual habitats of the black bear (e.g. Sadeghpour and Ginnet, 2011). American black bears are omnivorous (e.g. Gende et al., 2000), like us humans, in that they eat both plants and animals. Due to this fact, they are able to eat a wide range of things, which can vary depending on the season and specific habitat they live in, making them easy to please (e.g. Ecosystem Classification group, 2007). However, because of their large size, their must be a large, steady food supply for them to eat (e.g. Sadeghpour and Ginnett, 2011). Fortunately for bears, their lack of diet constraints means that they are not as selective in their habitats in comparison to other organisms. American black bears tend to inhabit regions with diverse vegetation, like shrubs, that they use for food. A typical diet of a black bear, in the summer months, consists of ground vegetation such as berries, grasses, roots, and tubers (e.g. Bartareau et al., 2012). Other vegetative species that black bears like to feed on are the Pacific Silver (Abies amabilis) and the western hemlock (Tsuga heterophylla) (Franklin and Dyrness, 1973; Stewart et al., 2002). However, as stated previously, black bears are omnivorous, so they also consume meat. Black bears choose deciduous and boreal forests, in part, because of the other species that reside in these regions for the bears to use as a food resource. Some of the species that bears will feed on are: salmon (Salmo salar), moose (Alces alces), caribou (Rangifer tarandus), marine caplin and carrion (e.g. Day, 1997). Although, as it starts to get colder black bears tend to lessen the amount of soft mast they take in and focus more on the hard mast, to increase their mass, in preparation for hibernation when they do not eat due to low food resources (e.g. Sadeghpour and Ginnett, 2011). They begin to add tree bark to their diet, while continuing to eat roots and insect nests (Bartareau et al., 2012; Stewart et al., 2002). Salmon is another resource that they increase in consumption for energy and fat-layer purposes before hibernating (Gende et al., 2000). While diet is essential to life for all organisms, American black bears do not live in regions solely for the diet aspect. American black bears hibernate in the colder months in the North American hemisphere. Typically, they are in hibernation starting around December and stay in their dens until April (e.g. Goodrich and Berger, 1993). This hibernation factor plays a role in habitat selection in that they need proper, safe shelter for when they go into dormancy, and the elements that are found in boreal and deciduous forests help them make their dens for those months. Bears, most popularly, make their dens in trees. However, they also use other places as shelter such as rock dens, logs, or even brush piles on the ground. The trees are not solely used as food and shelter resources, but also for protection and an escape route from predators (Garbeau et al., 2006) . In northern black bear habitats, they are not the only predator. Brown bears (Ursus arctos), are commonly found close to black bear habitats (Garbeau et al,. 2006). Black bears tend to avoid confrontation with other predators, specifically female black bears who usually build their dens in higher elevated areas (e.g. Herrero, 1978) This shows how black bears, females at least, tend to consider predators when choosing a habitat or place to den (Barnes, 1989; Miller, 1990). Black bears are solitary creatures, so they tend to stray away from interactions with other animals, including humans, which means they build dens with very little traffic, like in the mountains, for example (Goodrich and Berger, 1993; Novick et al., 1981). These regions are dense with both coniferous and deciduous trees which both play a big role in black bear survival. They are used as a food resource, means of escape, and also provide thermal covering for when it gets cold in the winter months (Sadeghpour and Ginnett, 2011; Fecske et al., 2002; ) Other popular tree species found in black bear habitats, according to Sadeghpour and Ginnett (2011), are paper birch (Betula papyrifera), red maple (Acer rubrum), aspen (Populus tremuloides), and different types of oaks (Quercus spp.). The different species of conifer trees that are found in these regions are: white pine (Pinus strobus), red pine (P. resinosa), jack pine (P. banksiana), balsam fir (Abies balsamifera), and black spruce (Picea mariana), and all play an important role in a black bears life. As you have read, there are several different factors that black bears consider when choosing a habitat. They have to think of their diet and what they eat. However, they are fortunate in that they tend to not have many diet constraints placed on them, other than in the fall months when they need to increase their mass size and uptake of hard mast in order to prepare for the dormant months of hibernation. Another important factor they must ponder with habitat selection is predators and how safe they will be. Since black bears are solitary creatures it is consequential to them to choose an area that is fairly free of other predators. The trees provide probably the most important role in a black bears survival because they aid the black bear in food resources, predator resources as a means of escape, and also as shelter. Black bears do not have many constraints placed on them by nature, but they do tend to restrict themselves to places dense with trees, and for good reasons! |
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