Polar Bears - Ursus maritimus - Literature review Example

Polar Bears Polar bears have been present on Earth for about four and a half million years ( Polar Bear International, 2014) , but been much in the news in recent years due to the problems they are having because of the melting and shrinking Arctic ice cap. The word Arctic is actually derived from the Greek word for bear with its opposite number Antarctic meaning an area without bears. This literature review will in the main be concerned with the viability of this species, Ursus maritimus. Thesis . Polar bears are adaptable creatures, but the present changes they face may be one change too many. Justification for this study Under the laws of the Endangered Species Act (2008) polar bears were included in the list of endangered species right across their range within the United States because of the potential shrinking of their preferred habitat as a result of climate change (Roach 2008). Method This idea will be investigated using a literature search, using search terms such as ‘polar bear; North pole ; ice cap; endangered species; polar bear ecology etc. The texts found will be considered for their relevance, and then conclusions will be drawn. Literature Search The whole of the Artic circumpolar area is the habitat of the polar bears, although the majority are to be found in modern times in northern Canada. Although most bears go into water on occasions, polar bears are especially adapted to live both on land, on ice and in the icy waters (Endangered Polar Bear 2013). The bears have longer necks, and smaller heads and ears when compared to other bears. Their seemingly white or yellowish fur coat consists of water repellent hair, with a very dense undercoat. It is so dense that if the bear runs on land so little heat is lost that the creature can actually overheat ( Polar Bear International, 2014) The apparent colour is affected by food eaten, the yellow coming from the seal fat from their prey, mainly ring seals. Their large feet help them to swim and spread their weight when walking on thin ice. The bottoms of their feet are almost covered in fur ( Alaska Department of Fish and Game). Their skin under all that fur is actually black which it was though allowed them to soak up the northern sun rays. In 1988 however, after careful experiments Koon and Hutchins proved this idea to be false ( Cited by Polar Bears International 2014). Their research showed that the black skin absorbs only tiny amounts of ultraviolet light rays. Instead keratin, a basic component of hair, was absorbing the ultraviolet light, although Lavigne, who discovered that polar bears absorbed UV light in 1988, has demonstrated that any energy gains taken from ultra violet light rays are very tiny and make little difference to energy levels( Koon, undated). Their fur appears to be white, but each hair shaft is actually pigment-free. The hairs are transparent with a hollow centre which scatters and reflects the available visible light ( Polar Bears International , 2014). They are excellent swimmers, reaching speeds in the open sea of 10 kilometres per hours, and, unlike their close relatives, having been spotted as far as 100 miles from either land or ice. The preferred habitat is on the offshore pack ice, and along coasts and islands within the Arctic region. This choice of habitat allows them to live in close contact with their main food source – seals. Polar bears prefer the ice packs to other parts of their habitat because it allows them to remain in close contact with their main food source, seals. When the short Artic summer comes the region finally warms up and the ice shrinks. This is when the bears find themselves forced to travel many miles on the ice in order to remain close to the seals, and the polar regions warm up, the polar bears will travel many miles to remain on the ice, near their food source, seals. Any bears which that do not stay on the ice when it begins to shrink might have to stay on land, until the icecap begins to grow once more in the autumn. These bears survive by living on the fat deposits built up during the previous winter. These lie immediately under the skin and can be as thick as 4.5 inches/ 11 cm (Polar Bears International, 2014). Populations began to shrink as long ago as the 1970s (Alaska Department of Fish and Game, 2014). It is claimed by the state of Alaska that this can be attributed to ‘trophy’ harvesting in the 1950s and 1960s when this was still legal. The polar bear is basically a killing machine on four legs. The largest of the land based predators, larger on average even than the Kodiak bears of southern Alaska, it is right at the top of the Artic marine food chain, yet The World Wildlife Fund (2014) stresses how important their top position in the food chain makes this species. All large carnivores are in this position as being indicators of the ecological position of their environment and food sources. In this case their diet consists of seals and other fatty marine mammals. The remains of their meals on these species then provide food for many other Arctic species, including the scavenger the Arctic Fox (Defenders of Wildlife, 2013). However in recent times thinner ice sheets and longer summer ice-free periods mean life is increasing difficult for the bears. Roach ( 2008) quotes American Secretary of the Interior Dirk Kempthorne as having said :- Because polar bears are vulnerable to this loss of habitat, they are—in my judgment—likely to become endangered in the foreseeable future. In 1973 the American Endangered Species Act became law (NOAA Fisheries, 2013). In order to be listed under this act a species is stated as :- Endangered if it is in danger of extinction throughout all or a significant portion of its range. Threatened if it is likely to become an endangered species within the foreseeable future. Such a description certainly fits the polar bear in the 21st century and (Defenders of Wildlife , 2013) it was the first marine mammal to be so listed. The WWF reported in 2014 that the total population is divided into 19 subpopulations or units. The latest data from the IUCN Polar Bear Specialist Group revels that eight of these subpopulations are in definite decline and that there is an estimated high estimated risk of further decline in the future because of ongoing climate change. The WWF explains the importance of the species as an indicator of changes in other populations ( WWF, Why they matter,2014). They list the species as ‘Vulnerable’ that is in danger of future extinction. In part this is because their prey species, the various fatty sea mammals, are also suffering from the ongoing climatic changes. Also these bears have no fear of humans so happily wander into towns where they are not wanted ( Luther , undated) Speaking of this in relation to polar bears, Kempthorne also explained how many scientists believe that the melting of the sea ice is directly related to global warming which is occurring as a result of human activity. Also oil exploration and drilling activities can also be a threat meaning that bears can be displaced from denning areas into locations they find to be less suitable. Also there is a danger of oil spills. Contact with any spilt oil could result in a reduction in the insulation capacity of their coats as well as being toxic to the bears. The presence of oil and the accompanying activities could also negatively impact their sources of food supply ( Alaska Department of Fish and Game, 2014). The scientists have urged the need to limit the emissions of greenhouse gases, but Kempthorne explains that to do so would be beyond the limits of this act. But Kempthorne said that science is not yet able to link specific activities such as carbon dioxide emissions from a coal-fired power plant to impacts on individual polar bears. Some would deny that there really is such a thing as global warming, but according to Stirling and Derocher ( 2012) the polar bears depend upon the presence of sea ice as a platform from which they hunt seals for enough time each year to allow them to accumulate sufficient body fat to give them, energy to survive for the long periods when seals are not so readily available. Shrinking areas of ice earlier and earlier in spring mean that the bears have less time to access their prey. The result is longer periods of enforced fasting, which lowers their general body condition. This in turn results fewer and smaller cubs being born as well as lower survival rates of these cubs, as well as their older relatives. In the Hudson Bay area scientists have discovered that the main cause of death of cubs is either food scarcity or less fat on nursing mothers. For each week earlier that the ice breaks up, bears are coming come ashore about 10 kg (22 lbs) lighter and in poorer physical condition (World Wildlife Fund, 2014) .Food scarcity could also mean that the bears look for other sources of food which then leads to conflict with their human neighbours. The arctic area is also becoming increasing polluted and these toxic substance enter the food chain causing such things as toxins being produced and consumed in breast milk and could poison cubs, lowering their survival rates ( World Wildlife Fund 2014). Bears who have high levels of some persistent organic pollutants (POPS) have been found to have lower levels than normal of vitamin A as well as some antibodies and thyroid hormones, These are all important for a range of bodily functions, such as reproduction, growth, and immunity , the capability to fight off disease. This combination of factors could possibly finally result in the extinction of particular subpopulations. The further south the population lives the greater the problem with Stirling and Derocher ( 2012) believing that this sub population will disappear by the middle of the 21st century, and, presumably at some point, the whole species, unless this process can be halted or even reversed. Post et al ( 2013) stress the need to address the pressures upon marine mammals which rise out of increasing human use of the arctic coastal and near-shore areas as sea ice shrinks year upon year, with an all time minimum being measured in 2012. So what can be done? It seems that part of the polar bears problems also include the contact they have with humans. Illegal hunting is a major problem according to WWF (2014). With climatic change have also come more opportunities for oil and gas development and as well as an increase in shipping in waters previously frozen for much of the year. Polar Bears International ( 2014) believe that it is not too late to reverse the situation. The group believe that even individual actions can make a positive difference. These include such things as :- Voting for those political representatives who recognize that our present carbon-based society is no longer sustainable. Encouraging members of their family and wider social circles to adopt more sustainable lifestyles. Seeing humanity as stewards of the world, raising awareness of how small lifestyle changes such as recycling and bike riding can make a difference. Such activities may not save all the polar bears, but they will make the world a better place to share with them. Conclusion It is clear that polar bears are powerful rather than ‘cute’ creatures, but they are also in danger. It may be though that even these adaptable northern giants may not be able to adapt easily to changing environmental conditions, especially those caused by global warming. The problem is wider however, as the species are at the top of a complex food chain and are therefore important, indicating by their presence, deterioration or absence, the more general health of local ecology. Scientists believe there is still some hope that the present deteriorating situation can be reversed, but it requires world-wide action on the part of humanity. What is required is the will, and the actions that develop out of it, both individually and collectively, to make an important difference. References Alaska Department of Fish and Game,( 2014), Polar Bear (ursus maritimus) (online) available http://www.adfg.alaska.gov/index.cfm?adfg=polarbear.main [20th March 2014] Defenders of Wildlife, (2013), Fact Sheet: Polar Bears, (online) available http://www.defenders.org/polar-bear/basic-facts [20th March 2014] Endangered Polar Bear, (2013), (online) available http://www.endangeredpolarbear.com/habitat.html [20th March 2014] IUCN/SSC Polar Bear Specialist Group, (2013), (online) available http://pbsg.npolar.no/en/ [20th March 2014] Koon, D., ( undated) Publications on the "fiber optics" of polar bear hair, (online) available http://it.stlawu.edu/~koon/mar_ref.html?level=1 [20th March 2014] Lavigne, D.,( August1988,) letter to Scientific American, (online) available http://www.scientificamerican.com/magazine/sa/1988/08-01/ [20th March 2014] Luther, C. (undated) Alaska Polar Bear Tours, (online) available http://traveltips.usatoday.com/alaska-polar-bear-tours-11871.html [20th March 2014] NOAA Fisheries, (2013), Endangered Species Act (ESA) (online) available http://www.nmfs.noaa.gov/pr/laws/esa/[ 20th March 2014] Polar Bear International, (2014), Tips from Top Scientists to Protect Polar Bears, (online) available http://www.polarbearsinternational.org/about-polar-bears/tips-scientists-help-polar-bears Post, E., Bhatt,U., Bitz,C., Brodie,J., 4, Fulton,T., Hebblewhite, M., Kerby,J.,Kutz,S., Stirling,I, Walker,D., (2nd August 2013), Ecological Consequences of Sea-Ice Decline, Science, Vol. 341 no. 6145 pp. 519-524 Roach, J, 2008, Polar Bears Listed as Threatened Species in U.S., National Geographic (online) available http://news.nationalgeographic.com/news/2008/05/080514-polar-bears.html [20th March 2014] Stirling ,I. and Derocher, A., ( September 2012), Effects of climate warming on polar bears: a review of the evidence, Global Change Biology , Volume 19, issue 9 2694–2706, (online) available http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2486.2012.02753.x/abstract;jsessionid=62769938264F54D830C38951708408B3.f03t03 [20th March 2014] The World Wildlife Fund, (2014), Species: Polar Bear, Overview, (online) available http://worldwildlife.org/species/polar-bear [20th March 2014] The World Wildlife Fund,( 2014), Species: Polar Bear, Why They Matter, (online) available http://worldwildlife.org/species/polar-bear [20th March 2014] Read More