Hi, everyone! This week’s ‘The “Inside” Scoop’ post is about the magnificent polar bear! The “Inside Nature’s Giants” episode that my post is based on was shot in an extremely remote location on the east coast of Greenland. In addition to the team shooting the necropsy footage, there were also Danish researchers in the town studying polar bear health. I usually love the episodes of this show because most of the ones I have seen take advantage of the unfortunate death of an animal to educate the public about their biology. However, in this episode, all the bears featured were killed from legal subsistence hunts. Watching this episode made me realize that I do not have a great background in how subsistence hunting works, so I hope to change that with a future post. Apparently, the native Greenland Inuit get a quota of about 30 bears per year. It is clear in the episode that not much food is available in the region, and the food that one can buy is extremely expensive. This makes the hunting more understandable from a living and cultural standpoint, but it was still challenging to watch the polar bear hunts. Just a forewarning. That being said, let’s get into the video. (Viewer discretion is advised, so stick to the time stamps below if you are squeamish).
7:05 – A polar bear has been killed for subsistence hunting. The Danish researchers studying polar bear health and the scientists conducting the TV show tried to exchange money with the hunters to collect samples/film the dissection before returning the bear to the locals. For this particular bear, the hunters refused the offer. This is the first time you really see the interactions between the Inuit and the research teams and get a feel for the culture.
11:44 – Short introduction to how pollutants get absorbed into food webs. Everything starts with phytoplankton (photosynthesizing microorganisms/microalgae), which can produce half of the Earth’s oxygen. Some phytoplankton blooms are so large that they can be seen from space! Pollutants from man-made chemicals and materials get into the food chain at the fundamental level of phytoplankton. The toxins begin to accumulate as one progresses higher in the food chain. In turn, apex predators, like polar bears or humans, end up with the highest concentrations of these toxins. As wind forces pollutants to accrue in the Arctic, there could be drastic effects on polar bear health. Consequently, humans consuming polar bear products would also be at increased health risks.
14:30 – Public/Educational outreach session about the importance of studying polar bear health and its connection to human health. I really liked this clip because it showed the cultural interface and highlighted the importance that outreach and public awareness can play in enacting scientific change.
16:36 – Getting into the culture behind subsistence. The hunters only kill lone polar bears, so they do not hunt any females seen with young cubs. This is meant to help maintain the population, but according to IUCN, polar bears are still considered vulnerable.
18:20 – The biologist tries on some clothing made from polar bear and seal skin.
19:00 – Polar bear fur is incredibly thick and allows hardly any heat to escape. The TV crew shows some great thermograph footage that reinforces just how little heat escapes a polar bear’s insulated coat. The bears can even sleep in -70 degrees (I think F, they didn’t clarify), and they will not freeze getting into/out of icy water.
20:24 – Checking out polar bear fur! Two main fur layers exist: deep fur (to lock in heat) and longer guard hairs (to keep snow and wind out). Polar bear skin is actually black (just like seals! I recently learned this at work!). The scientists looked at the fur through a microscope to see the hollow hair shafts. Interestingly, the actual hair is colorless, but because the hair is colorless and hollow, it reflects light and appears white. The colorless aspect also helps generate warmth because sunlight passes directly through the hair to the black skin, which subsequently absorbs the heat and radiates it back out to get recaptured within the fur.
24:25 – Richard Dawkins explains how being large in size can also help animals conserve heat. There is a physiological pattern that as body size increases, extremity size decreases (e.g. ears). Polar bears have relatively small ears compared to other types of bears.
26:18 – Section on the environmental challenges polar bears faced in their evolutionary history. Polar bears have been in the Arctic for over 150,000 years. However, their evolutionary story is difficult to piece together because few fossils exist, but DNA evidence has shown that 200,000 years ago a large ice age occurred. At this point in time, no polar bears existed, only brown bears. The ice age forced some brown bears south, but a small group of bears got caught between advancing ice boundaries. These bears needed to adapt or die, which gave rise to modern polar bears. Polar bears learned to hunt seals by finding their breathing holes from over 20 miles away!
29:14 – Analyzing the skull of a polar bear. The form is extremely streamlined and narrow. The biologists speculate that the design arose as an adaptation to hunting seals through their breathing holes.
30:30 – A seal hunting party via boat. This clip gives a closer look at the Inuit way of life. At 33:17 the biologists arrive on the scene of a walrus hunt. This particular walrus had a 2-inch fat layer. Humans cannot consume this much fat, but polar bears can eat up to 100 lbs of fat in one sitting! Polar bears often use scare tactics to trigger stampedes of walruses, thereby singling out a younger, weak walrus as prey (34:17).
37:00 – A polar bear was killed, and the locals are allowing researchers to obtain samples before dividing the bear amongst themselves. This bear was healthy and had a large storage of fat it could use during periods of food scarcity. Through health research, such as that shown in the episode, researchers have shown that polar bears appear to be having drastic reproductive alterations like reduced testes and enlarged clitorises. If radical changes continue, it could pose a huge threat to the species since it will inhibit their ability to reproduce.
42:25 – Scientists looking at blood and tissue samples back at the laboratory. Researchers explain that everyday items, like electronics, have flame retardant coatings that leach into the environment when they are disposed of. These chemicals could be contributing to the physiological alterations seen in polar bears.
43:45 – A brief hike through the mountains to find a polar bear den! Babies barely have any fat or fur when they are born. Polar bear dens are excellent at trapping the mother’s body heat so that the babies can stay warm. Mothers can stay in the den for 4+ months without going outside, feeding, or even defecating! Also, interestingly, mothers do not exhibit any bone or muscle degradation during this dormant period. I also did not realize this, but polar bears do not technically hibernate. The mothers go into a hibernation-like state. However, they do not exhibit the long periods of continuous sleep or decreases in body temperature that are characteristic of true hibernation. Clip at 45:30 shows cubs emerging from their den!
47:30 – Two polar bears are brought in from a hunt. The footage is rather disturbing because one bear is pulled through the water by a rope (already dead, but still sad).
51:20 – Quick look at the internal organs/digestive tract to try to understand how the bears can handle such a high-fat diet. 53:30- The stomach shows a recent meal of seal fur and skin. Polar bears focus mainly on fatty tissue and forego the muscle tissue. Such quantities of fat might cause high cholesterol and gallstones, but a polar bear’s gallbladder is full of bile and can digest high quantities of fat exceedingly well. Animation at 56:21 shows how fat is difficult to digest because it congests, but polar bear bile cuts right through it, splitting it into smaller molecules. Because bile is so important for a polar bear’s survival, they have more concentrated bile than other animals.
I hope you enjoyed learning about polar bear physiology! As I mentioned previously, it was not one of my favorite episodes because it was challenging to watch the subsistence hunts, but I still found the information about polar bear biology fascinating. I will try to do a post on subsistence hunting in the near future. It is definitely a topic that I would like to have a better grasp on. Have a great week!