Introduction
Environmental adaptation is essential to the survival of any animal. In fact, this attribute helps organisms obtain nutrients, build homes, withstand extreme weather conditions, attach mates and enhance their safety (Nelson et al. 2008). With this in mind, it is worth appreciating the fact that polar and grizzly bears have different physical and behavioral characteristics due to environmental adaptation in spite of their species similarities. The polar bear is specially adapted to survive in the cold pole regions. Its body structure and genetic composition have substantially evolved to accommodate the low temperatures and harsh environmental conditions. Its behavioral attributes are best suited for that environment due to ecological adaptations (Dorecher, Lunn & Stirling, 2004). On the other hand, Grizzly bears are best suited for survival in the warm and temperate regions. Their body structures cannot withstand low temperatures as the other animal. However, its behavioral interactions have made it possible to integrate with the forest environment thereby enhancing its survival. This paper evaluates the grizzly and polar bear lifestyles on their living conditions. Comparisons will be based on reproduction, behavioral, habitat and dietary preferences. For a fact, the environment and an organism’s habitat affect its behavior due to adaptation.
Reproduction
Grizzly bears
Reproduction is essential for the sustainability of an ecosystem by enhancing variation. As such, grizzly bears take part in this process to improve their survival chances. According to Pritchard and Robbins (2004), Grizzly bears are among the slowest reproducing mammals on land. This is mainly attributed to the fact that the females do not engage in reproductive activities until they are five years old. For this species, the mating season commences between May and July. Nonetheless, the female body delays the implantation of the ovum in the uterus until October or November making the overall reproduction process rather slow. Their Biology and Management argues that if a female grizzly bear does not gain enough muscle fat to last through the winter, implantation may not occur. During the hibernation period, the grizzly bear needs enough fat to last the time and to be utilized in the raising of the cubs that are to be born in that season (Jonkel, Kolenosky, Robertson & Russel, 2007). As such, the grizzly bear’s ability to accumulate enough fat is based on not only survival purposes but also reproductive benefits. The female mother bears take two to three years to take care of their cubs. It is worth noting that the male bears do not contribute to the raising of the cubs. In fact, the Canadian Journal of Zoology argues that they are a threat to the survival of the young ones, and so the mother bears tend to avoid them. The gestation period takes between 180 and 270 days. This span accommodates the delay in implantation. The female bears give birth to an average of 2-3 bears. However, four bears can be fostered in some rare occasions (Pritchard & Robbins, 2004).
Polar bears
According to Stirling and Parkinson (2006) mature polar bear and solitary. As such, they seek female mating partners during the early summer and late spring seasons. The polar bears couple for some few weeks before separating. The females begin the mating process at around the age of four. However, the male polar bears take a relatively longer time as they commence mating processes between five and six years. Nonetheless, their prime breeding age lies around ten years. After reproduction, the polar bears may live up to 9 months from their fat reserves during their pregnancy period. The breeding times lie between March and June on the sea ice. Nonetheless, this period occurs between April and May on some occasions. In the mating seasons, the males find the females by engaging in productive seal-hunting fights. Dorecher, Lunn and Stirling (2004) notes that the competition for females among the polar bears is significant as they have been recorded to track over 100km in search of their female counterparts. The gestation period for these bears takes about eight months. It is worth noting that this time caters for the delayed implantation. After successful implantation, the females begin accumulating fat in their tissues in preparation for the cubing processes. According to Nelson et al. (2008), the female bears can deposit a minimum of 200kg fat in their bodies during the mating season. The polar bear cubs are given birth to between November and January while in the den. The frequency of giving birth among these bears is one time every three years. The most common litter size is one and two bears. However, some rare occasions involve the birth of three to four cubs. The mother bear takes care of the cubs until they are thirty months old.
Comparison
Comparatively, the grizzly and the polar bears exhibit a wide array of similarities in their reproductive processes. For instance, the females commence reproduction processes at the ages of four of five in both cases. When this happens, the stronger and older male bears have the opportunity to engage in mating activities due to their physical size and strength. The male bears do not participate in mating activities until they are above five years old in both cases. Implantation delay is a common characteristic of the reproduction processes between the female polar and grizzly bears. The implantation delay takes between two and three months. Similarly, fighting for female bears is common between these two species. The male bears participate in hunting activities or physical fights to determine the suitable mating partners. Both bears also rely on fat reserves to provide energy during the winter and in the cubing process. The litter size is also similar for both organisms as they foster between one and four cubs. Nonetheless, there are few differences present between these bears. Primarily, they have a different gestation period. The grizzly bears have a longer one that stretches from 180 to 270 days (Cahill et al. 2013). However, the polar bear takes nearly eight months to give birth. Additionally, the care process slightly differs. The grizzly bears disassociate themselves from the males during cubing. However, polar bears do not have a limited association period after giving birth.
Climate and habitat
Grizzly bears
Grizzly bears are not limited to one geographical location. In fact, the Journal of Wildlife Management argues that they do not have a specific habitat to defend from other animals (Garshelis, Gibeau & Horrero, 2007). Nonetheless, they are mostly settled in foothills grasslands and thick temperate rain forests. Precisely, they are located in Alaska and the Coastal British Columbia. A bear’s habitat continually changes over the years depending on the type of season and the availability of food around the region. Due to their sizes and overall strength, the male bears occupy larger territories that may at times overlap those of the females and the weaker males. On average, the overall habitat for a grizzly bear lies between 500 and 2500km. The females, however, can secure territories lying between 200 and 500km. From a climate perspective, the grizzly bears are adapted to strive through changing seasons. During the winter months, they consume as much food as their bodies can allow and store the nutrients in their fat tissues. These reserves are later utilized for the winter period when there is lesser food supply. It is worth mentioning that the migration patterns during the summer period are rather mediocre. Most of the times are spent in hibernation and the utilization of the fat reserves. Consequently, the grizzly bear can survive in varying climatic conditions with moderate temperatures. Precisely, it can withstand the moderately cold winter and the hot summers. Nonetheless, it cannot withstand freezing conditions as opposed to other types of bears.
Polar bears
The most natural habitat for the polar bears is around the Arctic region. According to Molnár et al. (2011), the most favorable habitat for a polar bear encompasses the high winds and the accumulation of pack ice. The continuous ice formation and melting leads to the development of patches and water reservoirs that have favorable temperature conditions for the survival of these organisms. Preferably, polar bears are accustomed to the survival in this region, as it is the location where they can find the largest number of seals. During the summer period, as the sea ice melts leading to the accumulation of freezing water, the polar bears travel longer distances of over one thousand kilometers in search of food. Their distribution is evenly spread across Canada, Alaska, Norway, Greenland, and Russia. During the winter seasons, these bears occupy the sea ice locations, and they constantly engage in hunting activities. Their actions lead to the consumption of large amounts of food. Consequently, they process a lot of food nutrients later stored in the fat layers for the preparation of the winter season and the cubing process. However, when the summer period has harsh living conditions that minimize the amount of food supply, the bears migrate in search of food. Due to the dynamic nature of the Iceland, the bears do not have specific habitats. Rather, their active habitats and survival mechanisms are based on environmental conditions and the change in climate.
Comparison
Contrastingly, the polar and grizzly bears have a wide spectrum of differences in the type of habitats occupied and the favorable climatic conditions. Primarily, the grizzly bears are mainly adapted to survival in the warm temperate regions. As such, their habitats are based on woodland forests and foothills. They have a brown fur color to enable camouflage with the woodland environment. Additionally, they have a fat layer to store extra nutrients for the summer periods. As such, these adaptive features make it easier for this organism to survive in the temperate regions. Conversely, the polar bears are specially adapted to survive in the cooler Polar Regions. Precisely, their body structure can withstand adverse temperatures below the freezing point. For instance, their white fur enables them to blend in well with the ice and snow thereby augmenting their chances of survival (Cahill et al. 2013). Additionally, it has a fat layer that helps it keep warm in lower temperatures. Additionally, its thick layer of fur makes it lesser challenging to sustain the low temperatures. Its broad paws enable the bear to walk on snow and propel efficiently while swimming in water. Additionally, the fact that polar bears do not secure territories for their habitats makes them different from the grizzlies. The grizzly bears vast sizes of lands by securing their hunting areas. This significantly reduces their migration pattern in search of food as they base their survival on their habitats. However, the lack of specific habitats for the polar bears makes it challenging for them to survive in a particular geographical location.
Behavior
Grizzly bears
Similar to human beings, bears possess unique and shared behavioral activities. According to Wieglus & Bunnel (2006), understanding bear behaviors incorporates comprehension of the postures and overall vocalizations. Grizzly bears are usually shy and retiring animals that have a very minimal urge to interact with human beings. However, there are some rare occasions where bears integrate with people especially when they are the sources of food. Grizzly bears have a critical space that they must defend. Similar to other wild animals, bears fight off competitors seeking to occupy their habitats. Regarding defense, these bears have a large tendency to fight off their enemies as opposed to retreating. This is mainly accredited to the fact that they are poor tree climbers and cannot rely on treetops for safety. They have a heightened curiosity towards discovering things. This attribute is fostered by their strong sense of smell. According to the Journal of Wildlife Management, bears are not territorial meaning that they do not often keep other organisms away from their territories unless they pose a competitive threat (Garshelis, Gibeau & Horrero, 2007). It hibernates during winter to conserve energy and nutrients consumption due to the lower food supply.
Polar bears
The polar bears mainly prey on seals. Given the nature of their habitats, they live in small groups of five to augment their survival chances. They are solitary adults on most occasions apart from the breeding and mating seasons. The cold environment makes them develop pleasant swimming abilities. According to Thiemann, Iverson and Stirling (2008), polar bears are excellent swimmers as they have been recorded to swim as far as 200 miles away from land in search of food. However, they seldom use swimming as a locomotive alternative as it requires larger amounts of energy as opposed to walking. Younger bears do not swim as this activity has fatal effects on the survival of the bears. Only the breeding female bears hibernate during winter. As such, the males and the non-breeding females hunt and uphold the typical survival activities during this period. They constantly engage in pack wars to determine the strongest animal and a preferable male for mating. Polar bears are not territorial. As a result, they do not fight off other animals for invading their personal circles. Due to their strong sense of smell, they frequently engage in search activities to determine edible organisms or those suitable for play.
Comparison
The polar and grizzly bears have multiple similarities in their developmental activities. Primarily, they are not very territorial as such they do not fight other animals out of their habitats. Additionally, they have a tendency to migrate continuously in search of food. They are aggressive animals as they mostly engage in fighting off other organisms instead of retreating in the emergence of war. Their strong sense of smell makes them curious animals capable of engaging in search activities for food. These two types of bears move in small groups to enhance their survival chances. However, there are some striking differences between these organisms. According to Pritchard and Robbins (2004), their hibernation patterns are different since polar bears do not engage in long sleep periods unless necessary. Unlike grizzly bears, which hibernate during the entire winter period, only breeding polar bears indulge in this activity as a measure aimed to save energy for the mating period.
Conclusion
In conclusion, environmental adaptations significantly affect the behaviors of different organisms. In spite of the fact that polar and grizzly bears have an almost similar genetic markup, their exposure to various types of environments has led to the development of various survival behaviors. For instance, their structural appearance is best suited for the survival in particular circumstances. Polar bears have a thick fat layer to enhance their adaptation to the cold environmental conditions while grizzly bears have brown fur to improve their camouflage levels. Additionally, their behavioral responses are based on environmental changes. Precisely, their mating and hibernation periods are about the natural patterns. As such, the environment and an organism’s habitat affect its behavior due to adaptation.
References
Blanchard, B. M., & Knight, R. R. (2002). Movements of Yellowstone grizzly bears. Biological Conservation, 58(1), 41-67.
Cahill, J. A., Green, R. E., Fulton, T. L., Stiller, M., Jay, F., Ovsyanikov, N., & Shapiro, B. (2013). Genomic evidence for island population conversion resolves conflicting theories of polar bear evolution. PLoS Genet, 9(3), e1003345.
Derocher, A. E., Lunn, N. J., & Stirling, I. (2004). Polar bears in a warming climate. Integrative and Comparative Biology, 44(2), 163-176.
Garshelis, D. L., Gibeau, M. L., & Herrero, S. (2007). Grizzly bear demographics in and around Banff National Park and Kananaskis country, Alberta. Journal of Wildlife Management, 69(1), 277-297.
Jonkel, C. J., Kolenosky, G. B., Robertson, R. J., & Russell, R. H. (2007). Further notes on polar bear denning habits. Bears: Their Biology and Management, 142-158.
Molnár, P. K., Derocher, A. E., Klanjscek, T., & Lewis, M. A. (2011). Predicting climate change impacts on polar bear litter size. Nature Communications, 2, 186.
Nelson, R. A., Folk Jr, G. E., Pfeiffer, E. W., Craighead, J. J., Jonkel, C. J., & Steiger, D. L. (2008). Behavior, biochemistry, and hibernation in black, grizzly, and polar bears. Bears: Their Biology and Management, 284-290.
Pritchard, G. T., & Robbins, C. T. (2004). Digestive and metabolic efficiencies of grizzly and black bears. Canadian Journal of Zoology, 68(8), 1645-1651.
Stirling, I., & Parkinson, C. L. (2006). Possible effects of climate warming on selected populations of polar bears (Ursus maritimus) in the Canadian Arctic. Arctic, 261-275.
Thiemann, G. W., Iverson, S. J., & Stirling, I. (2008). Polar bear diets and arctic marine food webs: insights from fatty acid analysis. Ecological Monographs, 78(4), 591-613.
Wielgus, R. B., & Bunnell, F. L. (2006). Possible negative effects of adult male mortality on female grizzly bear reproduction. Biological Conservation, 93(2), 145-154.
