Global warming is causing an overall decrease in sea ice distribution and structure. Arctic ecosystems and populations are exhibiting large-scale fluctuations in comparison to the naturally observed climate cycles. Large alterations of habitats cause shifts in trophic interactions, which can eventually lead to extinction. Populations of polar bears and other pagophilic species have been negatively affected by the spatial and temporal ice changes. Over the past five years, the overall polar bear populations have decreased by over 20%, which classified the species as endangered.
How Do Polar Bears Cool Themselves?
To physiologically compensate for the increased temperatures, polar bears have superficial blood vessels on their muzzles, foot pads, nose, ears, and inner thighs that readily dissipate heat to the surrounding environment. Additionally, to reduce overheating due to energy exertion while hunting, their bodies store large amounts of fat to decrease how often they need to hunt. The fat deposits can also be oxidized to release carbon dioxide and water, which also assists in thermoregulation through sweat.
Furthermore, evolutionary behaviors allow polar bears to have external control over their body heat. Similar to other mammals, they often pant, swim, drink excess water, or seek shade to cool themselves down.
How are Polar Bears Acclimating to Climate Change?
Due to the loss of habitat, polar bears are seen progressively migrating into southern regions, which permits territory overlap with northernmost grizzly bears. Furthermore, the species have been interacting at an increasing extent, which has led them to mate and produce hybrids. The evolutionary extent of the interactions is unknown, but it is projected that this hybridization will result in a decrease in biodiversity and loss of adaptive gene combinations in both species.
Changing Food Supply
Polar bears rely on seals for their dietary needs. However, the loss of sheet ice caused a decrease in arctic areas for seals to raise pups, and, therefore, areas for polar bears to hunt. With the decline of food sources, they are forced to eat alternative prey to survive. A research team in Svlbard, an archipelago between Norway and the North Pole, observed a polar bear eat a dolphin. Furthermore, the bear buried the leftovers in the snow for later use. This behavior is extremely odd for polar bears because they normally do not hunt dolphins. Additionally, while other bear species commonly store food for later, polar bears do not.
Also, snow geese populations have increased in Canada, which has helped sustain polar bear populations. Many scientists have observed polar bears eat snow geese eggs as an alternative food source. While the eggs provide the polar bears with essential fatty acids and fat-soluble vitamins, it is not a resource that can sustain the population. If polar bears rely on this food source, snow goose populations will decrease into extinction.
Finding new places to hunt
With a declining hunting ground, polar bears continue to look for alternative areas to find food. Among the new areas are towns and residential areas occupied by humans. In these areas, the bears switched to eating human food and garbage for caloric intake. In response to this, officials in Arviat, Canada moved Halloween trick-or-treating indoors because children wandering around with candy increased their risk of being attacked by a polar bear.
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Resources: https://academic.oup.com/icb/article/44/2/163/674253, http://pubs.aina.ucalgary.ca/arctic/arctic60-3-271.pdf, https://www.ncbi.nlm.nih.gov/pubmed/20578846, https://www.ncbi.nlm.nih.gov/pubmed/21164461, https://www.sciencedirect.com/science/article/pii/S0006320710001473, https://news.nationalgeographic.com/2015/09/150904-polar-bears-dolphins-seals-climate-change/, https://onlinelibrary.wiley.com/doi/abs/10.1111/j.1600-0706.2010.18837.x, https://news.nationalgeographic.com/news/2010/11/101108-global-warming-polar-bears-snow-goose-eggs-science/, https://www.cbc.ca/news/canada/north/polar-bears-push-halloween-activities-indoors-in-arviat-nunavut-1.2800268
Picture Resources: Featured Image: https://pixabay.com/en/polar-bear-mother-cubs-white-1509103/, https://pixabay.com/en/dolphins-marine-mammals-diving-378217/, https://pixabay.com/en/polar-bear-swim-predator-bear-1381747/