Polar Bear
September 16th, 2008
The polar bear is classified as a vulnerable species. Of the 19 recognized polar bear subpopulations, 5 are declining, 5 are stable, 2 are increasing, and 7 have insufficient data. For decades, unrestricted hunting raised international concern for the future of the species; populations have rebounded after controls and quotas began to take effect. For thousands of years, the polar bear has been a key figure in the material, spiritual, and cultural life of Arctic indigenous peoples, and the hunting of polar bears remains important in their cultures.
Many scientist agree, that global warming is one of the most significant threat to the polar bear, primarily because the melting of its sea ice habitat reduces its ability to find sufficient food. Sea ice melting will also cause changes in their mating, and traveling patterns. The IUCN states, "If climatic trends continue polar bears may become extirpated from most of their range within 100 years." On May 14, 2008, the United States Department of the Interior listed the polar bear as a threatened species under the Endangered Species Act.
The polar bear is found throughout the Arctic Ocean and adjacent seas. Due to the absence of human development in its remote habitat, it retains more of its original range than any other extant large carnivore. While they are rare north of 88°, there is evidence that they range all the way across the Arctic, and as far south as James Bay in Canada. They can occasionally drift widely with the sea ice, and there have been anecdotal sightings as far south as Berlevåg on the Norwegian mainland and the Kuril Islands in the Sea of Okhotsk. It is difficult to estimate a global population of polar bears as much of the range has been poorly studied, however biologists use a working estimate of about 20,000-25,000 polar bears worldwide.
There are 19 generally recognized discrete subpopulations. The subpopulations display seasonal fidelity to particular areas, but DNA studies show that they are not reproductively isolated. The thirteen North American subpopulations range from the Beaufort Sea south to Hudson Bay and east to Baffin Bay in western Greenland and account for about 70% of the global population. The Eurasian population is broken up into the East Greenland, Barents Sea, Kara Sea, Laptev Sea, and Chukchi Sea subpopulations, though there is considerable uncertainty about the structure of these populations due to limited mark and recapture data.
The range includes the territory of five nations: Denmark (Greenland), Norway (Svalbard), Russia, US (Alaska) and Canada. These five nations are the signatories of the 1973 International Agreement for the Conservation of Polar Bears which mandates cooperation on research and conservations efforts throughout the polar bear's range.
Modern methods of tracking polar bear populations have been implemented only since the mid-1980s, and are expensive to perform consistently over a large area. The most accurate counts require flying a helicopter in the Arctic climate to find polar bears, shooting a tranquilizer dart at the bear to sedate it, and then tagging the bear. In Nunavut, some Inuit have reported increases in bear sightings around human settlements in recent years, leading to a belief that populations are increasing. Scientists have responded by noting that hungry bears may be congregating around human settlements, leading to the illusion that populations are higher than they actually are. The Polar Bear Specialist Group of the IUCN takes the position that "estimates of subpopulation size or sustainable harvest levels should not be made solely on the basis of traditional ecological knowledge without supporting scientific studies."
Of the 19 recognized polar bear subpopulations, 5 are declining, 5 are stable, 2 are increasing, and 7 have insufficient data.
The polar bear is often regarded as a marine mammal because it spends many months of the year at sea. Its preferred habitat is the annual sea ice (that is, ice that melts for part of the year) covering the waters over the continental shelf and the Arctic inter-island archipelagos. These areas have relatively high biological productivity in comparison to the deep waters of the high Arctic. The polar bear tends to frequent areas of open water, such as polynyas and leads (temporary stretchs of open water in Arctic ice) to hunt the seals that make up most of its diet. Polar bears are therefore found primarily along the perimeter of the polar ice pack, rather than in the Polar Basin close to the North Pole where the density of seals is low.
Annual ice contains areas of water that appear and disappear throughout the year as the weather changes. Seals migrate in response to these changes, and polar bears must follow their prey. In Hudson Bay, James Bay, and some other areas, the ice melts completely each summer (an event often referred to as "ice-floe breakup"), forcing polar bears to go onto land and wait through the months until the next freeze-up. In the Chukchi and Beaufort seas, polar bears retreat to the multi-year ice (that is, ice that remains solid year-round) further north each summer.
On May 14, 2008 the U.S. Department of the Interior listed the polar bear as a threatened species under the Endangered Species Act, citing the melting of Arctic sea ice as the primary threat to the polar bear. However, the department immediately issued a statement that the listing could not be used to regulate greenhouse gas emissions, saying, "That would be a wholly inappropriate use of the Endangered Species Act. ESA is not the right tool to set U. S. climate policy." However, some policy analysts believe that despite the government's stance, the Endangered Species Act can be used to restrict the issuing of federal permits for projects that would threaten the polar bear by increasing greenhouse gas emissions. Environmental groups have pledged to go to court to have the Endangered Species Act interpreted in such a way.
While listing the polar bear as a threatened species, the Interior Department added a seldom-used stipulation to allow oil and gas exploration and development to proceed in areas inhabited by polar bears, provided companies continue to comply with the existing restrictions of the Marine Mammal Protection Act. The main new protection for polar bears under the terms of the listing is that hunters will no longer be able to import trophies from the hunting of polar bears in Canada.
The polar bear is only the third species, after the elkhorn coral and the staghorn coral protected under the Endangered Species Act due to global warming. In August 4, 2008, the state of Alaska sued U.S. Interior Secretary Dirk Kempthorne, seeking to reverse the listing of the polar bear as a threatened species, out of concern that the listing would adversely affect oil and gas development in the state. Alaska Governor Sarah Palin said that the listing was not based on the best scientific and commercial data available, a view rejected by polar bear experts.
The ruling followed several years of controversy. On February 17, 2005 the Center for Biological Diversity filed a petition asking that the polar bear be listed under the Endangered Species Act. An agreement was reached and filed in Federal district court on June 5, 2006. Pursuant to that agreement, on January 9, 2007, the US Fish and Wildlife Service proposed to list the polar bear as a threatened species. A final decision was required by law by January 9, 2008, at which time the agency said it needed another month.
On March 7, 2008, the inspector general of the U.S. Interior Department began a preliminary investigation into why the decision had been delayed for nearly two months. The investigation is in response to a letter signed by six environmental groups that U.S. Fish and Wildlife Director Dale Hall violated the agency's scientific code of conduct by delaying the decision unnecessarily, allowing the government to proceed with an auction for oil and gas leases in the Alaska's Chukchi Sea, an area of key habitat for polar bears. The auction took place in early February 2008. An editorial in The New York Times said that "the two moves are almost certainly, and cynically, related." Hall denied any political interference in the decision and said that the delay was needed to make sure the decision was in a form easily understood. On April 28, 2008, a Federal court ruled that a decision on the listing must be made by May 15, 2008; the decision came on May 14.
Polar bears are also popular in fiction, particularly in books aimed at children or young adults. For example, The Polar Bear Son is adapted from a traditional Inuit tale. Polar bears feature prominently in East (also released as North Child) by Edith Pattou, The Bear by Raymond Briggs, and Chris d'Lacey's The Fire Within series. The panserbjørne of Philip Pullman's fantasy trilogy His Dark Materials are sapient, dignified polar bears who exhibit anthropomorphic qualities, and as such feature prominently in the 2007 film adaptation of The Golden Compass. The TV series Lost has shown polar bears on a mysterious tropical island.
Penguins
July 14th, 2008
The largest living species is the Emperor Penguin (Aptenodytes forsteri): adults average about 1.1 m (3 ft 7 in) tall and weigh 35 kg (75 lb) or more. The smallest penguin species is the Little Blue Penguin (also known as the Fairy Penguin), which stands around 40 cm tall (16 in) and weighs 1 kg (2.2 lb). Among extant penguins larger penguins inhabit colder regions, while smaller penguins are generally found in temperate or even tropical climates (see also Bergmann's Rule). Some prehistoric species attained enormous sizes, becoming as tall or as heavy as an adult human (see below for more). These were not restricted to Antarctic regions; on the contrary, subantarctic regions harboured high diversity, and at least one giant penguin occurred in a region not quite 2,000 km south of the Equator 35 mya, in a climate decidedly warmer than today.
Most penguins feed on krill, fish, squid, and other forms of sealife caught while swimming underwater. They spend half of their life on land and half in the oceans.
Penguins seem to have no special fear of humans and have approached groups of explorers without hesitation. This is probably on account of there being no land predators in Antarctica or the nearby offshore islands that prey on or attack penguins. Instead, penguins are at risk at sea from predators such as the leopard seal. Typically, penguins do not approach closer than about 3 meters (10 ft) at which point they become nervous. This is also the distance that Antarctic tourists are told to keep from penguins (tourists are not supposed to approach closer than 3 meters, but are not expected to withdraw if the penguins come closer).
Penguins are superbly adapted to an aquatic life. Their wings have become flippers, useless for flight in the air. In the water, however, penguins are astonishingly agile. Within the smooth plumage a layer of air is preserved, ensuring buoyancy. The air layer also helps insulate the birds in cold waters. On land, penguins use their tails and wings to maintain balance for their upright stance.
All penguins are countershaded for camouflage – that is, they have a white underside and a dark (mostly black) upperside. A predator looking up from below (such as an orca or a leopard seal) has difficulty distinguishing between a white penguin belly and the reflective water surface. The dark plumage on their backs camouflages them from above.
Diving penguins reach 6 to 12 km/h (3.7 to 7.5 mph), though there are reports of velocities of 27 km/h (17 mph) (which are more realistic in the case of startled flight). The small penguins do not usually dive deep; they catch their prey near the surface in dives that normally last only one or two minutes. Larger penguins can dive deep in case of need. Dives of the large Emperor Penguin have been recorded which reach a depth of 565 m (1,870 ft) and last up to 22 minutes.
Penguins either waddle on their feet or slide on their bellies across the snow, a movement called "tobogganing", which conserves energy while moving quickly. They also jump with both feet together if they want to move more quickly or cross steep or rocky terrain.
Penguins have an average sense of hearing for birds; this is used by parents and chicks to locate one another in crowded colonies. Their eyes are adapted for underwater vision, and are their primary means of locating prey and avoiding predators; in air it has been suggested that they are nearsighted, although research has not supported this hypothesis.
Penguins have a thick layer of insulating feathers which serve to keep them warm in water (heat loss in water is much greater than in air). The Emperor penguin (the largest penguin) has the largest body mass of all penguins, which further reduces relative surface area and heat loss. They also are able to control blood flow to their extremities, reducing the amount of blood which gets cold, but still keeping the extremities from freezing. In the extreme cold of the Antarctic winter, the females are at sea fishing for food leaving the males to brave the weather by themselves. They often huddle together to keep warm and rotate positions to make sure that each penguin gets a turn in the center of the heat pack.
They can drink salt water because their supraorbital gland filters excess salt from the bloodstream. The salt is excreted in a concentrated fluid from the nasal passages.
Modern penguins consititute two undisputed clades and another two more basal genera with more ambiguous relationships. The origin of the Spheniscinae lies probably in the latest Paleogene, and geographically it must have been much the same as the general area in which the order evolved: the oceans between the Australia-New Zealand region and the Antarctic. Presumedly diverging from other penguins around 40 mya, it seems that the Spheniscinae were for quite some time limited to their ancestral area, as the well-researched deposits of the Antarctic Peninsula and Patagonia have not yielded Paleogene fossils of the subfamily. Also, the earliest spheniscine lineages are those with the most southern distribution.
The genus Aptenodytes appears to be the basalmost divergence among living penguins; they have bright yellow-orange neck, breast, and bill patches; incubate by placing their eggs on their feet, and when they hatch the chicks are almost naked. This genus has a distribution centered on the Antarctic coasts and barely extends to some subantarctic islands today.
Pygoscelis contains species with a fairly simple black-and-white head pattern; their distribution is intermediate, centered on Antarctic coasts but extending somewhat northwards from there. In external morphology, these apparently still resemble the common ancestor of the Spheniscinae, as Aptenodytes' autapomorphies are in most cases fairly pronounced adaptations related to that genus' extreme habitat conditions. As the former genus, Pygoscelis seems to have diverged during the Bartonian, but the range expansion and radiation which led to the present-day diversity probably did not occur until much later; around the Burdigalian stage of the Early Miocene, roughly 20–15 mya.
The genera Spheniscus and Eudyptula contain species with a mostly subantarctic distribution centered on South America; some, however, range quite far northwards. They all lack carotenoid coloration, and the former genus has a conspicuous banded head pattern; they are unique among living penguins by nesting in burrows. This group probably radiated eastwards with the Antarctic Circumpolar Current out of the ancestral range of modern penguins throughout the Chattian (Late Oligocene), starting approximately 28 mya. While the two genera separated during this time, the present-day diversity is the result of a Pliocene radiation, taking place some 4–2 mya.
The Megadyptes–Eudyptes clade occurs at similar latitudes (though not as far north as the Galapagos Penguin), has its highest diversity in the New Zealand region, and represent a westward dispersal. They are characterized by hairy yellow ornamental head feathers; their bills are at least partly red. These two genera diverged apparently in the Middle Miocene (Langhian, roughly 15–14 mya), but again, the living species of Eudyptes are the product of a later radiation, stretching from about the late Tortonian (Late Miocene, 8 mya) to the end of the Pliocene.
The geographical and temporal pattern or spheniscine evolution corresponds closely to two episodes of global cooling documented in the paleoclimatic record.
Inside this group, penguin relationships are far less clear. Depending on the analysis and dataset, a close relationship to Ciconiiformes or to Procellariiformes has been suggested. Some think the penguin-like plotopterids (usually considered relatives of anhingas and cormorants) may actually be a sister group of the penguins, and that penguins may have ultimately shared a common ancestor with the Pelecaniformes and consequently would have to be included in that order, or that the plotopterids were not as close to other pelecaniforms as generally assumed, which would necessitate splitting the traditional Pelecaniformes in three.
The Auk of the Northern Hemisphere is superficially similar to penguins: they are not related to the penguins at all, but considered by some to be a product of moderate convergent evolution.
Theese little creatures are adored everywhere in the world. They are extremly popular. Featured in many cartoons, movies, toys are made like penguins and they are quite a big part of the Arctic wildlife.
