AP BIOLOGY ANIMAL NEWS MAY 8, 2014

! PAGE 1

Project by: Alejandro Anderson and Patrick Huggins

The Polar BearThe predator of the Arctic Circle.This animal is at the top of its food chain, but there is more to the polar bear than meets the eye.

May 8, 2014 – The scientific name of the polar bear, Ursus maritimus, translates from Latin to “sea bear”. As this name would suggest, the polar bear is linked to the Arctic Ocean environment, and is dependent on the seal it hunts offshore. Balancing on sheets of ice between dives, polar bears are actually quite bulky, using their fat stores as insulation and a source of energy. Males can weigh in anywhere from 500 to 1,750 pounds, while the smaller females weigh about 330 to 550 pounds.! The polar bear species originated in the Arctic Circle. Polar bears are thought to have evolved from an isolated population of brown bears at some point in the ice age between 100,000 to 250,000 years ago, during the mid-Pleistocene period. During this time period, glaciers covered almost all of Europe, Asia, and North America. In fact, the Arctic Ocean was completely frozen. It is

believed that the brown bears were in search of food and wandered across these glaciers. About 125,000 years ago, the brown bears that were located in the Arctic Circle found themselves isolated due to the shifting glaciers. Polar bears currently live in the arctic tundra, specifically in northern North America, and Northern Asia. These are Arctic areas located just south of the northern polar ice cap.! Polar bears are NOT found in Antarctica. However, the environment they live in is similar to that of Antarctica's: extremely cold, and only well-adapted organisms can survive because of the harsh conditions. The arctic tundra got its name from the Finnish word “tunturia” which refers to a treeless plain. That is what the arctic tundra is, cold, icy, windy, extremely sunny in the summer, extremely dark during the winter, treeless, and founded on permafrost. The permafrost is a thick subsurface of soil that remains frozen year round. During the winter, the temperature is around -29 F (34 C). During the summer, the temperature is around 29 F (-1.7 C).

The  image  to  the  right  is  of  a  polar  bear  in  its  natural  habitat.  Polar  bears  are  known  for  resting  on  chunks  of  ice  while  swimming  in  the  Arctic  Ocean.

AP BIOLOGY ANIMAL NEWS MAY 8, 2014

! PAGE 2

It isn’t uncommon for the temperature to plunge down to -58 F (-50 C) during the winter. Most of the area averages around 20 inches of precipitation (mostly in the form of snow/ice), while parts of Greenland see around 47 inches of precipitation every year. There are about 1,700 different species of plants that live in the arctic tundra. These includes, flowering plants, herbs, mosses, grasses, small shrubs, and lichens (similar to fungi and algae). Other animals that live in the arctic tundra include the snowy owl, Canada lynx, tundra swan, arctic hare, arctic fox, beluga whale, caribou, narwhal, and seal. The biome does not experience many natural disasters. Blizzards are the most common natural disasters that occur. However, the arctic tundra has been facing problems and drastic weather changes as a result of global warming. The temperature has increased, the ice has been melting, and the plants and animals are seriously affected. The permafrost has continued to melt and thaw out. The melting of the permafrost releases more greenhouse gases, and many of the plants and animals are struggling to adapt to the drastic changes.

! The polar bear resides along the coastal areas of northern North America, Greenland, and northeast Asia. Polar bears even live on moving masses of ice. The only density-dependent regulators that affect polar bears are global warming and competition for resources. Global warming has affected the number of living polar bears in the Arctic. It has melted many of the ice masses that were once homes to the polar bears, which has led to

a decrease in polar bear population. This problem has grown significantly and has caught the attention of many nations and their citizens. Even though the polar bear is not at the top of the endangered species list, if the temperatures of the planet continue to go

up, the polar bear population will drop even further. Additionally, competition for resources has increased amongst the polar bear population. Food can be scarce, from a lack of seals, to a lack of edible vegetation. There is a limited amount of food sources for polar bears in the Arctic Circle.

! Male polar bears dominate a territory that includes the territories of multiple female polar bears. As an apex predator, the polar bear does not have any adaptations to defend itself from any natural predators. However, when males come in contact with one another, they often compete over mates with violent fighting. These fights can drag on for several weeks, and result in death or severe, long-lasting wounds for both bears. Females that refuse to mate with males may be attacked or abused. These female polar bears receive scratches and bite marks from mating refusals and from defending their cubs from violent males. Less often, orca whales have been known to kill and eat polar bears that are caught while swimming. Humans, while not a natural predator of polar bears, will occasionally hunt them as trophies. Despite a lack of natural predators on a higher trophic level, the polar bear population is shrinking. Even more threatening is the fact that genetic diversity amongst the diminishing polar bear population is dangerously low.

Polar Bears: Top of the Food Chain

AP BIOLOGY ANIMAL NEWS MAY 8, 2014

! PAGE 3

! The polar bear treats all other species it encounters as its prey. However, when there is an abundance of seal, the polar bears will only eat their prey’s fat, leaving the flesh for arctic scavengers. The polar bear’s diet mainly consists of seal and the carcasses of beluga whales, walruses, and grey and bowhead whales. On land, polar bears will hunt muskox and reindeer as well as waterfowl and rodents. They will also scavenge for kelp, shellfish, eggs, berries, and human garbage.

THE HUMAN IMPACT

! Humans have had a direct and multi-faceted impact on the decline of polar bears. Human contribution to the climate change known as “global warming” is the most noticeable of these. In the southernmost polar bear territories, warmer temperatures are leading to fewer weeks of the year in which ice conditions are suitable for hunting. Without the ice as a hunting platform, polar bears must wait longer to begin their hunting season and return to shore earlier. For every week of hunting they miss, they will have 22 fewer pounds of body fat than they naturally would. This has led to local extinctions in southern polar bear territory, caused almost entirely by starvation and low milk production for cubs. Human pollutants are often most

dangerous to apex predators, because the concentration of toxic substances increases as energy passes up each trophic level. Pesticides and other industrial toxins filter up the food chain and are found in high concentrations in polar bears’ bodies and milk. This toxic milk may directly poison and kill young cubs. The pollutants’ effects on the polar bears’ bodies range from low immune systems to pseudohermaphroditism in females. From human presence alone, oil exploration in the arctic disturbs the polar bear populations. Any oil spills are extremely difficult to contain in the harsh environment. Oil contamination of polar bear territory can poison the bears or soak the fur coats of the animals. Polar bears with oily coats cannot conserve heat as effectively, and they burn more calories each hour to stay warm. On top of these indirect detriments to the species, humans will occasionally hunt polar bears for their fur and meat. Humans are intervening in the stability of the polar bear population by working to reverse their negative

indirect impacts on the species. In addition to constantly monitoring the populations of polar bears, humans are working towards living more sustainable lifestyles. By consuming less energy, people can reduce their carbon output, thereby lessening their contribution to the melting of polar ice.

! As the top predator of the arctic tundra, polar bears serve as an ambassador to a region of our planet responsible for global climate and sea levels. Any slight changes to the bottom of their food chains become noticeable effects among the polar bear population. In this respect, they act as a measuring stick of human impact, giving us a biological perspective on our impact on the polar ice caps. By closely observing these creatures in collaboration with climate observation and measuring the recession of the polar ice caps, humans will be able to more accurately understand the changes occurring on the planet.