Please also see Polar Bears International‘s website for more FAQs about polar bears.
There are different approaches to studying the genetics of polar bears however it all comes down to one thing, quality DNA.
DNA contains the biological instructions that make an individual unique and is often referred to as the genetic fingerprint. DNA can be derived from blood, tissue, hair and feces of a bear. In the field, we acquire these samples during our handling of an immobilized bear or opportunistically. For example, during a polar bear census we may encounter a previously unidentified bear. An ear tag with a distinct set of letters and numbers would be inserted, giving rise to a small tissue sample. This hole-punched sized tissue sample would be placed into a tube and sent to the lab for processing.
In the lab we would extract the DNA from the sample through a two-day protocol using a molecular kit. This process involves the break-down of the tissue, removal of contaminants and potential inhibitors of quality DNA. By the end of the process, we have a quantity of concentrated DNA that we can then use to for further experiments.
Such experiments may include polymerase chain reaction (PCRs) where amplification of a known specific sequence of DNA occurs. This product is run on a sequencer where we can then visually see if bear sample contains that known sequence of DNA. The combination of presence and absence and other varieties of the known sequence reveals a unique identifier we call a genotype.
We can distinguish bears based on their genotype. With this useful genetic information we can go on to infer relatedness and thus build a pedigree. Similarities and differences do exist amongst polar bears at varying levels, which can aid in our understanding of how to manage their populations.
By Alysa McCall
Each spring in the Beaufort Sea and fall in western Hudson Bay, we put out about 4-10 satellite-linked GPS collars on female polar bears. We are not able to collar males because their necks are wider than their heads, so the collar can slip off easily. We adjust the collar to make sure it’s not too loose or too tight, and program it to communicate the location of the polar bear to a satellite every four hours. We get regular email updates with each polar bear’s new locations.
This technology has been critical for scientists to gain a better understanding of what polar bears actually do out on the sea ice. It is expensive, dangerous, and sometimes physically impossible to get to where polar bears roam during the winter. Therefore, if we want to know when they move, how far they travel, and where they go, GPS collars are our best option. Each collar can cost up to as much as $6000, but this is well worth the knowledge that we gain. By knowing when and where polar bears travel at certain times of the year as well as the areas of highest use and lowest use, we can get a better idea of what regions are most important for polar bears. This knowledge lets us ask a variety of questions about polar bears that would never be possible without GPS collars and can even help us to better focus our conservation efforts.
New research is showing the potential of finding and tracking polar bears using only satellites, no collars needed. This research is very exciting and could help us get a better idea of how many polar bears there are worldwide and their distribution at different times of the year. However, if we want to know about individual bears across time, weights, sizes, pregnancies, stress levels, DNA, etc., we still need to do hands-on field work.
As the ice sheet retreats, oil and gas companies move ever further into polar bear habitat. In fact, the two often occupy the same areas. The effects of this are complex, and could affect the polar bears in a number of ways, directly as well as indirectly. The different factors are all more or less interrelated, but I will try my best to give some sort of overview here. (I’ve added links at the bottom to further explain some of the terms).
First off, any kind of oil related activity (seismic surveys*, construction of rigs, increased shipping and helicopter traffic) creates a noisier environment, above as well as below water. Although polar bear dens reduce ambient noise by a certain level, pregnant females may avoid denning in particularly noisy areas. In addition, increased disturbance levels in the already occupied denning areas may lead to den abandonment and thus reduced cub survival. Increased noise levels could also affect the ecosystem around the polar bears, for example the pagophilic (“ice-loving”) seals that are by far the polar bear’s main prey. The seals might abandon their usual pupping grounds if these are being disrupted by human activities or the open ice leads** created by shipping/sailing, and may thus (like the bears) have to select sub-optimal breeding areas instead. Sub-optimal seal pupping grounds could lead to thinner seal pups or even increased pup mortality, both of which are of low energetic value to polar bears; polar bears need to gorge on fat seal pups each spring – the weight a bear puts on during this short period is critical for its survival as well as its reproductive success (thinner mothers produce fewer and less viable cubs). On a side note, the open leads created by increased shipping during the ice-covered season could ultimately also present another problem energetically to the polar bears, as moving between bigger open areas between ice floes requires extra energy.
Another source of impact is related to pollution, especially oil spills. These could be spills from tankers, holes in underwater pipelines, or uncontrolled release of oil – e.g. an underwater blowout*** such as the recent one in the Gulf of Mexico. Stopping a blowout or even cleaning up after any substantial oil spill in ice-covered Arctic waters, often windy and very remote, is nigh impossible. In addition, such oil spills would be likely to concentrate in ice leads, which is also where you find seals (sunbathing on the ice along the leads, or simply using the leads as breathing holes) and thus also polar bears. The results of any major oil spill could thus have extensive consequences for the entire Arctic ecosystem, including seals and polar bears. To exacerbate any such situation, polar bears actually seem to be especially attracted to the smell of oil and oil-based products. Some examples include cans of oil, snow scooter parts, lead acid battery, antifreeze mixed with dye, and hydraulic oil – all of which indicates that polar bears would happily eat a bird or a seal that was covered in oil. In addition, polar bears are very clean animals that take excellent care of their fur – the functioning of which is essential to their staying warm – and have been shown to try and lick their fur clean if contaminated with crude oil (e.g. from an oil slick on the water). There are several problems with this. First of all, polar bear fur covered in oil loses the majority of its insulative properties. In fact, polar bears soiled in oil have been found to use up to 86% more energy to stay warm than they would normally. Secondly, oil is a highly toxic chemical substance and, if ingested, can kill even polar bears very quickly. Bears that have been observed consuming oil died of kidney failure, but also suffered lung, liver, and brain damage. Finally, by showing no avoidance of oil, polar bears are extra vulnerable to exposure in case of any oil spills.
In addition to oil spills, any oil rig and related ship and air traffic would also act as a local source of other pollutants (organic contaminants****, CO2, black carbon*****), released on a daily basis during construction and normal operations.
Lastly, any kind of increased human activity in the Arctic brings with it a potential increase in the number of human-bear interactions – especially since polar bears are curious creatures and likely to be attracted by the novel sounds, sights, and smells. In addition, the previously mentioned man-made leads in the sea ice (from shipping as well as around the oil rig itself) tend to attract seals, which in turn attract polar bears, thus inadvertently leading a higher number of bears into human proximity. Any hostility during these encounters typically results in acts of self-defence by threatened humans, which rarely end well for bears.
As you can see from this exceedingly brief summary, the potential effects on polar bears of Arctic oil exploration and extraction cover a broad spectrum. Overall, the latent consequences are far-ranging, but not yet well known. However, this is very likely to change with in the near future, as the sea ice continues it retreat and the oil and gas companies continue their push to drill for resources in the Arctic.
*Seismic surveys: http://www.britannica.com/EBchecked/topic/532921/seismic-survey
***Oil blowout: http://en.wikipedia.org/wiki/Blowout_%28well_drilling%29
****Organic contaminants: http://en.wikipedia.org/wiki/Persistent_organic_pollutant
*****Black carbon: http://en.wikipedia.org/wiki/Black_carbon#Impacts
In theory, yes, we could move some or even all polar bears from the Arctic to Antarctica. At least for a while, they would probably thrive, feasting on the penguins and Antarctic seals. Antarctic animals are not used to any predatory threat while on land, so they would likely not even try to flee the bears. It would all be one big polar bear buffet!
This, obviously, would also be one of the biggest problems with introducing polar bears to Antarctica. The bears would wreak absolute havoc on the Antarctic ecosystem – even if it were to happen, a chase on land between a polar bear and a penguin is no contest, and very soon the penguin populations would be severely decimated. The same would likely happen to the seals, not least because polar bears would be able to eat their way through the seal pupping fields with no problems – especially since Antarctic seals give birth on the open ice and not in birth lairs under the snow (as the, to polar bears all-important, Arctic ringed seal does). In other words, what started out as a feast for the polar bears would soon turn to famine instead, as the available prey would disappear, leaving the bears with nothing to eat.
While this devastation of the Antarctic ecosystem would be the most obvious reason to not move bears to Antarctica, there are other considerations too. For example, though similar at a first glance, Antarctica is on average much colder than the Arctic, with temperatures easily going as low as -60 degrees Celsius (-76 degrees Fahrenheit). Polar bears are well insulated, but not for temperatures this low and would this require massive amounts of food year round to provide them with the energy necessary to stay warm and alive. Sufficient prey may not be available all year round, and the bears could thus end up freezing to death.
Logistics would be another challenge – which bears would you move? How would you catch them? And, importantly, who would pay the simply enormous cost of such a project?
So to sum up…yes, moving polar bears to Antarctica could be done, but it would create more problems than it would solve. Polar bears evolved in the north and are superbly and perfectly evolved for the Arctic environment that they inhabit. Moving polar bears to Antarctica in the hope of saving the species would be an extremely shortsighted solution indeed, and I would strongly suggest that we focus our energy on curbing climate change and saving the bears’ Arctic ice habitat instead.
Well, keeping in mind that polar bears are large mammals and that their cubs only weigh 500-800 grams when they are born, a polar bear’s pregnancy won’t be directly visible, even in the late fall when the pregnant female is about to enter her maternity den to give birth. However, especially during the fall months there is one telltale sign to look for, one that can be seen even from a distance, and that is how fat the bear is (the bear’s body condition). Pregnant polar bears need to eat as much as possible in the summer and fall months in order to build up the needed fat reserves to survive the denning period. Doubling or even tripling in weight before denning is completely normal for a pregnant polar bear! (When you’re out scouting for pregnant bears though, remember that a young male and a slightly older female bear can sometimes be hard to distinguish from each other at a distance. In other words, although a fat bear observed in the fall is likely to be a pregnant female, it could also just be a young male bear with great seal hunting skills…).
Another way of telling if a polar bear is pregnant is to measure the level of pregnancy-related hormones in the bear’s urine or feces (more or less in the same way as with human pregnancy tests). However, polar bear pee and poop samples are not easy to gather in the wild, and so the method has till now only been used in zoos (blood samples obtained from sedated animals have, on a few occasions, been used instead for wild polar bears). One zoo even trained a dog to be able to tell if a female polar bear was pregnant or not by simply smelling the bear’s poo! (See http://www.zooborns.com/zooborns/2013/11/beagle-sniffs-out-pregnant-polar-bears.html).
I have attached a picture to give you some idea of how female polar bears can look while pregnant. The picture shows a pregnant female in exceedingly good body condition (bears this fat are rarely encountered anymore). This particular bear was so chubby that the researchers couldn’t fit the normal satellite radio collar on her, but had to glue a smaller radio transmitter to the top of her head instead in order to be able to track her movements. The female bear must now live off of only this body fat for up to an incredible 8 months, using the energy from it to keep herself alive but also to produce milk for her cubs. It cannot be emphasized enough how important it is for the survival of polar bears as a species that especially the pregnant females have good hunting conditions and the chance to be in superb body condition before entering the maternity den.
(Photo courtesy of Dr. Ian Stirling via http://www.sciencebuzz.org/sites/default/files/images/WEB_super_fat_female.preview.jpg).
Some people think of the Arctic sea ice as a giant ice platform fixed in place. But, actually, most sea ice is highly mobile. Only the sea ice close to land and in shallow areas can be anchored in place. We refer to this type of ice as landfast or shorefast ice. In contrast, most sea ice flows are in areas that are too deep and too far from shore for them to remain stationary. This type of sea ice will be moved by the wind and with ocean currents. In fact, on very windy days, sea ice can move multiple kilometres a day! As sea ice forms in the fall and melts in the spring, the amount landfast ice and moving ice will change. For example, most landfast ice will be melted in late summer, leaving only moving sea ice. Polar bears spend a lot of time on moving ice. Thus, understanding the movement of sea ice is important if we want to understand the movement behaviour of polar bears.