American Bears

American Bears

The Miocene Epoch, roughly 23 million years ago, is when the fossil record for the bear family (Ursidae) first appeared (Britannica, n.d.; Burt & Grossenheider, 1976; Nowak, 1999). Since then, bears have grown to be the largest terrestrial carnivores in the world (Burt & Grossenheider, 1976). North America is home to three different bear species: black bears (Ursus americanus), brown bears (Ursus arctos), also referred to as grizzly bears, and polar bears (Ursus maritimus). The main topics of discussion will be about black and grizzly bears.

Dissemination

In general, bear habitats are found in a variety of ecosystems, from tropical jungles to arctic ice flows (Krause et al., 2008; Nowak, 1999; Schwartz, 2012). Black bears, in general, favor forested settings, but grizzly bears appear to favor open spaces like tundra, alpine meadows, and seashores (Nowak, 1999).

The distribution of black bears

American Bears

Black bears were distributed across pre-European settlement, from Mexico to Alaska and from the Atlantic Ocean to the Pacific Ocean (Unger et al., 2013). In many places, black bear populations have grown and shrunk over time. Fortunately, numerous restoration initiatives have been successful in reintroducing them to states where they had previously gone extinct. Today, they may be found in 40 of the 50 U.S. states and all but one of Canada's provinces and territories (BearSmart.com, n.d.).In some places, like the southern Californian highlands, Texas' Trans Pecos region, and portions of the Canadian tundra, where the grizzly bear was eradicated, the black bear has expanded its range (Unger et al., 2013; Nowak 1999). The remaining black bears in Louisiana and Florida are a distinct subspecies and are listed as threatened by the federal government (defenders.org, 2012).

Distribution of Grizzly Bears

In the past, the range of grizzly bears in North America included Alaska, Mexico, and the Dakotas. Some believe they were widespread in the Great Plains before the arrival of the Europeans (Nationalgeographic.com, n.d.; Nowak, 1999). Grizzly bear home ranges have significantly shrunk in modern times. In Canada, you can find them in the Northwest Territories, Yukon, and Alberta. Their range includes Alaska, Wyoming, Montana, Idaho, and Washington in the United States (BearSmart.com, n.d.). Under the Endangered Species Act, the United States has designated grizzly bears as threatened. The health of the grizzly bear populations in Canada is a major issue, and some provinces have listed them as threatened (Schwartz et al., 2012).

Formed along the coasts of Alaska and Canada, grizzly bears frequently become significantly larger, prompting scientists to further divide them into several geographic subspecies. Burt and Grossenheider, 1976; Nowak, 1999; BearSmart.com, n.d. In addition, the smaller grizzly bears that live in Canada's western arctic's icy, treeless wilderness are known as barren ground grizzly bears (Struzik, 2006).

COMMUNITY STRUCTURE

Except for females with young and groups of bears in locations with big food caches, bears are individualists by nature. Because of this, a bear's life is frequently spent wandering alone or hibernating. This does not imply that they lack social skills or engage in no bear-to-bear interaction. When there is a lot of food concentrated in one place, especially among known bears, dominance hierarchies can develop. While some bears appear to get along better with one another than others, some do not. Contrary to various depictions, they are typically calm animals who want to stay out of fights. (Nowak, 1999; BearSmart.com, undated).

Bears start to put on weight as winter nears and continue to do so until it's time to hibernate. Grizzly and black bears both experience full mammalian hibernation. Hibernation is a response to seasonal food shortages, chilly weather, and snowy terrain. Depending on the mammal species, hibernation physiological processes can vary. When compared to humans, bears have respirations that drop from 6–10 breaths per minute to one every 45 seconds, a metabolic rate that drops by 50–60%, a heart rate that drops from 40–50 beats per minute to 8–19 beats per minute, and a body temperature that drops from 38–31 degrees Celsius. While hibernating, neither grizzly nor black bears eat, drink, feces, or urine.They rely on their body's fat reserves to keep them alive during this protracted slumber, which results in a loss of up to 15 to 30 percent of their body weight. Furthermore, when urea is catabolized into nitrogen, waste materials are recycled. Using this nitrogen, protein is created to maintain organ and muscle tissue (USNPS, 2015).

While bears sleep, other physiological systems are also changed. For instance, bears continue to produce feces when they are hibernating, but the feces will gather into a plug in the anus to keep the bear from urinating on the location where it will build its lair. Additionally, bears do not develop osteoporosis from prolonged non-weight-bearing positions, unlike other mammalian species that do. A bear's cholesterol will also increase when it is hibernating. However, unlike humans, they do not develop gallstones or experience artery hardening during this time of hypercholesterolemia (USNPS, 2015).

Black Bear Social Organization

When not hibernating, black bear social behavior is influenced by plant development, fruiting, and food availability. However, they often stay away from one another and frequently protect their territory from other bears or outsiders. Other traits of black bear behavior include the use of a range of vocalizations, such as a startling "woof" sound, a harsh growl during conflict, or a piercing wail by cubs during times of loneliness or fear (Burt & Grossenheider, 1976; Nowak, 1999).

Black bears mature sexually between the ages of four and five for females and between five and six for males. The height of the mating season often occurs around mid-June. During this time, a single female is only in estrus for one to three days. Females often wait 3–4 years before giving birth, but this does happen occasionally. 220 days pass during pregnancy. On the other hand, delay in implantation results in autumn-starting and ten-week-long embryonic development. Births happen in January and February, frequently during the winter months (Nowak, 1999).

Black bear hibernation can start as early as late September and last as long as May, depending on the local conditions. During warm weather seasons, they only occasionally leave their burrow to get some fresh air. Fallen trees, hollow logs or trees, or burrows are typically the components of den sites. Black bears can have litters of one to five cubs. The eyes of newborn bears are closed. Weaning happens after 6 to 8 months (Defenders.org, 2012; Burt & Grossenheider, 1976; Nowak, 1999).

The mother and cubs will leave the nest site in the spring to avoid hostile adult males during the breeding season. The second winter, the cubs spend it with their mother. Mothers typically allow their daughters to encroach on their territories while tolerating their children within them. Young boys move away from their birthplaces, an average distance of 61 kilometers. Black bears occasionally live for thirty years or longer (BearSmart.com, n.d.; Burt & Grossenheider, 1976; Nowak, 1999).

Grizzly Bear Societal Organization

There is no evidence of territorial defense in grizzly bears, with the exception of the violence shown in dominance hierarchies. Where food is sufficient, they will even organize family foraging groups with a range of ages. In contrast to males, female grizzly bears have relatively smaller home ranges, but they also exhibit the highest hostility towards their offspring. Large adult males tend to stay away from crowds and occasionally murder cubs. Adolescent bears are the least aggressive bears in the hierarchy of dominance (BearSmart.com, n.d., Nowak, 1999).

Male grizzly bears will fight over females during the breeding season. For one to three weeks, the winner will breed with the female. With delayed implantation, mating occurs in the months of June and July. Development of the fertilized egg will start in October or November. During hibernation, between January and March, babies are born. There might be as little as one cub and as many as four in each litter. The eyes of newborn cubs are closed. Each cub weans at five months and stays with its mother for several springs (usually no less than two and no more than four). After leaving their mother, siblings frequently continue their social interactions for several years. Ages four to six are considered sexually mature for both sexes.

Grizzly bears hibernate from October through May, depending on the area, the climate, and the bear's health. Some southern regions do not experience hibernation. The bears frequently dig their dens out of dry grass. Locations beneath a sizable rock or the roots of sizable trees on a protected hillside are preferred. These locations are frequented every year (Nowak 1999).

While feeding or roving throughout the day, grizzly bears frequently seek shelter in deep cover even though they prefer more open territory. As dusk falls, they start to move and feed, and they continue doing so until dawn. In coastal Alaska, the larger bears are active all day long. Grizzly bears frequently travel during the seasons to find food sources like fish and places with abundant berries (Nowak 1999).

Expression

Bears often have a huge head, a body that is powerfully muscled, short, strong limbs, a short tail, and small eyes. It has short, rounded, and upright ears. Five digits on each limb have recurved claws at the end that are used for tearing and digging. They move with a well-known plantigrade shuffling stride (the heel of the foot touches the ground when walking). Most bears can travel short distances on their rear legs. They also have a keen sense of smell, although their senses of hearing and sight are less developed (Burt & Grossenheider, 1976; Nowak, 1999).

DIET

Bears spend a lot of time searching the forest for a variety of foods. Throughout the year, as the seasons change, so do their eating preferences. Rivers, streams, sunny south-facing slopes, wetland meadows, river valleys, avalanche slopes, aspen forests, marsh borders, and dump sites are examples of typical feeding locations. They are regarded as omnivorous because both plants and animals constitute a part of their diet. In some situations, plants can account for 90% of a person's diet (BearSmart.com, n.d.).

White Bear Diet

Fruits and vegetables make up 35% of the diet of black bears. Fruits, berries, honey, tubers, nuts, acorns, grass, sapwood, and roots are among these. Insects, fish, rodents, carrion, eggs, and occasionally larger mammals make up the remaining 25% of their diet. Black bears frequently eat garbage from dumps (Burt & Grossenheider, 1976; Nowak, 1999).

The Diet of Grizzly Bears

The primary components of a grizzly bear's diet include plants and other animals. They use their large claws to dig as necessary as they search for overwintered berries, grasses, sedges, roots, mosses, bulbs, and other starch-rich foods

roughout the early spring (BearSmart.com, n.d.; Burt & Grossenheider, 1976; Nowak, 1999). This shifts to succulents and perennial forbs as the season goes on. Berries, bulbs, and tubers are important components in autumn. Their diet also includes carrion, mice, ground squirrels, marmots, ants, beetle larvae, and other insects. In the Canadian Rockies, grizzly bears go for moose, elk, caribou, mountain sheep, and mountain goats. In areas where their habitats overlap, the grizzly bear also preys on black bears and competes with them for food (BearSmart.com, n.d.; Nowak, 1999).

A diet of anadromous salmon may explain the disparity in size between brown bears on the Alaskan and Pacific coasts and the smaller grizzly bears found in interior North America. Greater concentrations of these coastal bears can be found where salmon migrate upstream. Additionally, they frequently develop larger than elsewhere in their range (Nowak 1999).