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Trophic Relationships Among Arctic Species
(Click Image to Enlarge)
Original Diagram
Images taken from:
http://animals.nationalgeographic.com/arctic-animals |
The effects of ice loss in the Arctic not only impacts the polar bears livelihood but also the livelihoods of other arctic species. The pacific walrus, bearded and ringed seals, and arctic wolves, all use the ice for hunting, mating, and migration. The factors that are creating a decline in polar bear populations can also be seen in these other arctic species. Even terrestrial dwelling caribou are affected. The current research and data available is more prevalent towards the polar bear than the other species. From my research on polar bears, I have learned a lot about the impacts that could apply to other Arctic species that interact with and live in the same environment as the polar bear. Unfortunately the outlook for these Arctic species is all the same. Loss of sea ice equals a continually decreasing population and a very harsh day to day life.
Pacific Walrus, Bearded and Ringed Seals:
All three of these species utilize the sea ice in the same way. The ice is used primarily for resting, socializing, mating, and migrating. Seals and walruses need to breach the surface for air every five to fifteen minutes. When they come up for air, if a predator threat is not sensed, they will flop onto the ice and congregate with others of their species (6). The loss of ice has decreased their effectiveness to evade predatory species like the polar bear and arctic wolves. Less ice means fewer places for them to rest on without having to be aware of predators (6). It also means that predators would have a smaller area within which to hunt. The number of places available for seals and walruses to mate has also been reduced. Additionally it takes away a platform from which they can hunt for fish that are swimming beneath the ice. The last big impact on seals and walruses are changes in migratory patterns (8). Both species use the presence and loss of ice for different seasonal changes as a cue to know when to move to better hunting grounds and climate zones (8). With ice not fully returning in the winter and not being present in the summer, the times at which both of these species migrate has been altered. All of these consequences for both species are leading to decreases in overall fitness, smaller body masses for both adults and pups, decreases in longevity, and places to live (10). Like the polar bears, their fate is sadly the same. Their populations could severely decrease by mid century and could ultimately be nonexistent by the end of the century (10).
Arctic Wolves:
Like polar bears, Arctic wolves use the sea ice to hunt for seals and scavenge for any type of food they can find, dead or alive. They also use it for mating and some for making their den. The ice is a major part of their way of life so they are just as at risk as the polar bears. With the loss of sea ice comes a decrease in the seal population. Arctic wolves primarily feed on seals and caribou. They will also trail where polar bears have been and scavenge off of their leftover prey. As the ice continues to decrease so will the populations of species that the Arctic wolves rely on. Without their main food sources, the adults and the pups will go hungry. The pups are already being born in smaller quantities each year due to inadequate food sources (6). Increasing ice loss will decrease pup success and adult body mass (10). This will lead to decreased Arctic wolf fitness and populations, as the global warming trend continues through time.
Caribou:
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Caribou Grazing on Lichen
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Caribou are destined for the same fate, declining populations. The two key climate-related factors influencing caribou are snow depth and summer insect harassment (10). Caribou, although usually successful in their harsh habitat, must often work hard to forage through deep snow for the moss and lichen that is their main food source during the long Arctic winters (10). They must also make the most of the small tundra shrubs they feed on during the brief summer. The summer is also a crucial period for calving and lactation. Insect harassment by mosquitoes and parasitic flies may significantly decrease foraging time during the summer (6). Any changes that make foraging more difficult on a consistent basis would threaten the herds. Increased winter snow depth and summer insect harassment are likely to reduce food availability, increase energy requirements, and make caribou more vulnerable to predators such as wolves (6).These projected impacts suggest that continued climate change is likely to reduce caribou populations. A caribou decline would reduce the availability of food for predators, which greatly affects both the Arctic wolves and the polar bears, who will hunt them if seals are scarce (10).
I thought the affects on other organisms was an interesting addition to the information on polar bears. It may be helpful though, to show how these species interact with one another and the polar bears as well to show the larger "sea ice" ecosystem as a whole. I feel this would help make this page fit more into your larger argument about polar bears.
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