Polar Bears- Ursus maritimus
Polar bears, Ursus maritimus also known as a sea bear, has evolved about 5 million years ago from brown bear ancestors. They are also mammal vertebrates. Polar bears are different from the brown bear mainly because they have adapted to living and surviving in freezing temperatures and ice habitats. Polar bears are very important in the overall health of the marine environment. They are at the top of the food chain and provide population balance in the artic habitat. They are also important because these bears depend on the sea ice for their existence and directly are impacted by climate change therefore serving as an important indicator species.(6) Listed below is polar bears full classification. (1)
|Scientific Name:||Ursus maritimus|
Range and habitat:
Polar bears live mainly in ice habitats. They have been found in the Arctic, Canada; which is where 60 % of the worlds polar bears live, Alaska, Greenland, Russia, and Norway. (1) Polar bears are one of the few mammals to spend more time at sea than on land. (3) There have been 19 populations of polar bears living in four different ice regions in the Arctic. (1)Their habitat range has been decreasing over time. Global warming has been negatively effecting the habitat and as well as the population of polar bears. The summer ice melt is happening earlier and faster every year. (1) This affects the polar bears by leaving them with less time to hunt on the ice before is all melts away. In 20 years the ice-period in Hudson Bay has increased by 20 days. This cuts the polar bear seal-hunting season by three weeks. This results in a smaller timeframe to hunt during the critical season when seal pups are born. Because of this, the average polar bear weight has dropped by 15 percent and reducing reproduction rates. (3) The ice is where polar reproduce, the more ice that melts away the less space there is for polar bears to mate and raise their young. (3) They also have no place to catch their breath after swimming for long periods of time and they end up drowning from exhaustion. The U.S. Geological Survey projects predict that two thirds of polar bears will disappear by 2050. (3)
Physical description and image:
Polar bears are extremely large mammals and can weigh up to 1500 pounds! Females can weigh up to 800 pounds. Males can grow up to 10 feet in length and females can reach up to 8 feet. Polar bears have very sharp claws to make it easier for walking on the snow and ice. The claws are also shorter than other bears so they can dig and scoop the ice. They also have pads on the bottom of their feet to protect them from being on the ice all the time. It also gives them traction so they wont slip when they are walking or running. (2) Polar bears are considered very talented swimmers! They can swim a constant pace of six miles per hour by paddling with their front paws and holding their hind legs flat like a rudder. (6)
The fur on the polar bear is dense with an insulating undercoat mixed with guard hairs in different lengths. Surprisingly the hair on a polar is not white, but is actually pigment free and transparent. Polar bears are white because of the way the light and snow reflects onto their fur. Polar bears look the whitest when they are clean and are in bright sunlight. They have a molt period where the lose some of their fur and this also makes them look very white. They have also been known to look a little yellow but this is due to the oils from the seals they eat. In 1979, at the San Diego Zoo, their polar bears turned green due to colonies of algae growing in their hairs. Polar bears have black skin and layer fat of that is around 4.5 inches thick. When they are on land the thick fur coat is what keeps the polar bear warm and prevent heat loss. When they are in the water polar bears use their fat layer to keep them warm. (5)
Polar bears have evolved rapidly to take advantage of an empty ecological niche as a predator of seals. Some of the rapid changes that have occurred are(9):
· White-yellow fur. This helps them camouflage and sneak up on their prey.
· They have claws to grasp fleeing prey.
· Their feet are heavily furred to provide warmth.
· They have smaller ears to avoid freezing
· Polar bears have a narrower and more elongated skull. this is an adaptation to warm the cold inhaled air, to aid the sense of smell, or to assist with the capture of prey trying to slip through a narrow opening to the safety of the sea below.
· They only have four mammae; brown bears have six, and a smaller litter size. This is an adaptation to the harsh environment for raising young.
In the Arctic the air temperatures are around-29 F in the winter and 32 F in the summer. The ocean temperatures in the arctic drop to 29 F in summer and 28 F, which is the freezing point of seawater. There is not much interactions between polar bears and other species because there Artic area is so vacant. An interesting fact about polar bears is that many people usually group penguins and polar bear together but they actually will never come into contact with each other. They live in opposite poles, polar bears live in Arctic and penguins live in Antarctica.(1) There is not much interactions between polar bears and other species. Mostly the only species they come into contact to are seals. Polar bears prey on ring seals, bearded seals, hooded seals, and harp seals. (9)
Polar bears show some pretty complex behavior. One interesting fact is the adult female bears with cubs hunt only about 19 % of their time during the spring. They hunt about 38 % during the spring and about 40% of their time during the summer. When they are not hunting polar bears often spend their time with sleeping or resting. When there is not a lot of ice around from July to December, preventing it from seal hunting they are know to spend 87 % of their time resting. When it is warm out side some bears sprawl out on the ground and make snow pits to lie in. As for their social life polar bears are mostly solitary, usually there is only two social units; females with cubs and breeding pairs. The most constant and strong social interaction is between the mother and her cubs. She is known to actively touch and groom them. The cubs will stay with their mother for around two years. After separating from the mother the siblings will usually stick with each other for a while. The breeding pairs remain together for around a week and they mate several times. There is some aggression that occurs between males during breeding season where there is competition for females. They are also known for play fighting between cubs and adults. Polar bears are one of the few bears to not hibernate during the winter. Only pregnant females do and its not the typical hibernation. The term hibernating means to pass the winter in a lethargic stage. When food is scarce animals hibernate living off of stored body, their heart rate, respiratory and body temperature drops. This does not happen to polar bears. They go through what is called a state of carnivore lethargy. Their body temperatures do not drop intensely and other body functions still continue. (8)
The current standing for Polar bear conservation is vulnerable according to the WWF. Polar bears are listed as threatened in the United States under the Endangered Species Act in May 2008. (6) The polar bear population is ranged from 20,000-25,000. Climate change is a huge factor of why polar bears are threated. The WWF are doing many things in order to help polar bears survive. The WWF has really pushed for a statement that will show the urgent need that will address the faults for climate change and what it is doing to the polar bears. Service in the communities where polar bears are common such as Alaska and Russia has been done by the WWF to prevent unintended encounters between polar bears and people. There is a polar bear patrol that helps keeps the communities safe. Some examples are having better lighting near public places, electric fencing, bear-proof food storage containers and warning plans for when bears enter the town. (6) Scientists and the WWF also run polar bear trackers to monitor the animals by satellite. From this they can map the polar bears range and how they use their habitat when it changes.
There was a study done by Stapleton etal. in Nov 2014. They evaluated satellite images as a tool to track where polar bears are and the abundance. These scientists looked at images from a small island in Foxe Basin, Canada. There was a high density of polar bears during the summer free ice season. From their study they concluded that satellite imagery is a great tool for monitoring polar bears on land. Some future research they suggested was to access the utility of multi-spectral imagery and examine sites with different environmental characteristics.(7) This study is important to polar bears because it is a way to track them and keep a hold of population sizes. This way scientist can know how the species is doing in terms of endangerment. They can also look at patterns between a natural disaster that occurs or the amount of ice that is melting and compare the population size.
1. Where Do Polar Bears Live? Polar Bears international. 2014. Retrieved December 1, 2014, from http://www.polarbearsinternational.org/polar-bear-facts-information/where-do-polar-bears-live
2. Polar Bear Anatomy. Bio Expedition. 2014. Retrieved December 1, 2014, from http://www.polarbear-world.com/polar-bear-anatomy/
3. Global Warming and Polar Bears - National Wildlife Federation. National Wildlife Federation. 2014. Retrieved December 1, 2014, from http://www.nwf.org/Wildlife/Threats-to-Wildlife/Global-Warming/Effects-on-Wildlife-and-Habitat/Polar-Bears.aspx
5. Fur and Skin. Polar Bears International. (2014). Retrieved December 1, 2014, from http://www.polarbearsinternational.org/about-polar-bears/essentials/fur-and-skin
6. Polar Bear Species WWF. World Wildlife Foundation. (2014) Retrieved December 1, 2014, from http://www.worldwildlife.org/species/polar-bear
7. Stapleton, S., LaRue, M., Lecomte, N., Atkinson, S., Garshelis, D., Porter, C., & Atwood, T. (2014). Polar Bears from Space: Assessing Satellite Imagery as a Tool to Track Arctic Wildlife. Plos ONE, 9(7), 1-7. doi:10.1371/journal.pone.0101513
8. Polar Bear. Behavior. SeaWorld (2014). Retrieved December 1, 2014, from http://seaworld.org/animal-info/animal-infobooks/polar-bears/behavior/
9. Derocher, A. (2000). Polar Bears and Climate Change. Retrieved December 1, 2014, from http://www.actionbioscience.org/environment/derocher.html