CRACKING THE CURIOUS CASE OF THE GROLAR BEAR
Overview Welcome to the Grolar Bear Challenge created by the Discovery Educator Network and Polar Bears International. Take part in this challenge before watching our webcast to better understand how bears size up to other creatures, compare grizzly and polar bears, learn about the rare grolar bear, and use your own creativity to help us problem solve.
Then join us on Tuesday, November 10 at 1 p.m. (ET) for a live webcast from the tundra where PBI’s panel of Arctic experts, plus the Discovery Educator Network’s Lance Rougeux, will discuss grizzly, polar, and grolar bears and how we use technology to understand the world around us.
The questions in this challenge range from basic math to high-level creativity. Some questions have no right answer, but are designed to get students thinking outside of the box. Practicing problem solving gives students the tools and determination to figure out real-world problems they might encounter.
You can view the answer key here.
Discovery Education Resources From video segments to boards to interactive glossary terms, there are hundreds of resources in Discovery Education about polar and grizzly bears to help you in this challenge. A few of our favorites include:
Also, search “polar bear” within Discovery Education and explore our brand new content collection.
1. Animal Birth Weights Every species must reproduce to keep surviving; it’s a fact of life! Because this is such a basic part of the life cycle, it may seem like it should be pretty simple and safe for the mother. However, giving birth can be
dangerous for many animals, especially if the baby is large compared to the mother. Mothers who have very large babies compared to their own bodies are at greater risk for complications, whereas moms that have very small babies compared to their own bodies may face fewer risks during birth. We can use birth weight ratios between mothers and babies to tell us how big the baby is compared to its mother. A high ratio means the baby is large compared to its mother, while a low ratio means the baby is small compared to its mother. For example, we know that humans have large babies compared to the mother’s size, what we call a high birth weight ratio. Luckily, medical science has helped humans give birth more safely in the last century. To give an example, a 120 lb. woman can give birth to an 8 lb. baby. To find the baby:mother ratio, we take 8:120. Simplified that means 1:15 is the birth ratio. The baby is 1/15th the size of mom, or the mom is 15 times bigger than the baby.
Another example: The Kandula Asian elephant mom is 10,000 lbs. and her baby at birth is 324 lbs. That means the baby:mother ratio is 324:10,000 or 1:31. So the baby is 1/31 the size of mom.
a. Just based on birth ratios, who might have the easier time giving birth? Elephants or humans?
b. Bears have the smallest baby:mother ratio of any placental mammal. Baby bears are very tiny, pink, and helpless when they are born, helping to ensure the mother has an easy birth. They are nursed for months by their mothers before emerging into the world. Mei Xiang, the giant panda mom, weighed 238 lbs. when she gave birth to her two cubs. Her first cub was only 0.19 lb. So, 0.19:238 or 1:1256. This mom was 1256 times larger than her first cub. Mei Xiang’s second cub was 0.30 lb. How many times larger was Mei Xiang compared her second cub?
c. For grizzly, or brown, bears, the mom has one to four cubs (usually two) every two years. Cubs are small and weigh only about 1 lb. at birth. If a mother grizzly bear weighs 300 lbs. when she gives birth to a 1 lb. cub, what is the baby:mother birth weight ratio?
d. Polar bears are very similar to grizzly bears in their birth weight ratios, but slightly different in the number of cubs they produce. A polar bear female may start giving birth after 5 years of age and has between 1 and 3 cubs each cycle. If a polar bear female starts reproducing at 5 years old, gives birth to an average of 2 cubs every 3 years, and lives until she is 24, how many cubs will she have produced in her lifetime?
2. Adaptations Polar bears and grizzly bears are closely related; in fact, polar bears evolved from a grizzly bear ancestor. These bears have similar DNA and anatomy and can interbreed to produce hybrid offspring. Though they are genetically similar, each species has special adaptations that allow them to exploit different resources. Adaptations can change the way an animal or plant looks or the way it behaves, help it to survive the cold, the heat, to camouflage, and much more. Adaptations make different species unique and able to survive and thrive in their own habitat.
For example, hibernation is a behavioral adaptation that grizzly bears have. In the winter, when the grizzly bear's food is covered by snow or unavailable, grizzlies enter their dens and hibernate throughout the winter. Hibernating lowers the grizzly bears’ body temperatures, heart rate, and need for energy. The need for food and water is eliminated and the bears are able to live off fat they stored on their body in the summer and fall.
Male polar bears do not hibernate or slow their metabolism down at any point during their lives, even when there is little to no food available. Pregnant polar bear females enter dens in the fall, give birth in the winter, and emerge with their cubs in the spring to hunt seals. Though they are in dens and slowing down, even female polar bears don’t exhibit true hibernation but can go up to 8 months without eating.
Grizzly bears have many other adaptations that help them find food and survive. For example, they have a distinguishing shoulder hump that is actually a mass of muscle, which enables brown bears strength to dig. Also, their claws are long, making them useful in digging for roots or digging out burrows of small mammals. Grizzly bears also have a range of teeth that have evolved to manage the variety of foods these bears eat. They have some sharp canine teeth but also flat molars that are well suited to eating and grinding vegetation.
Polar bears’ heads are longer and narrower than grizzly bears’ allowing them easier access into seal holes. Their noses are very large to smell well, and their small, round ears are fur-covered, inside and out to prevent heat loss. Polar bear claws are shorter and more strongly curved than grizzly bears’, and larger and heavier than black bears’ claws, used for hooking seals in the water and dragging them onto sea ice. Polar bear teeth are sharp, and have evolved for grabbing prey and shearing meat. Unlike grizzly bear teeth, polar bear teeth are not well equipped for chewing vegetation.
a. Thinking of adaptations, what advantage do grizzly bears have in being brown, and polar bears have in being white?
b. Polar bears live in much colder conditions than grizzly bears. Can you think of at least two other adaptations that help polar bears survive in their icy home?
c. From what you know so far, if you put a grizzly into polar bear habitat, how well do you think the grizzly would do at hunting seals? What advantages or disadvantages might a grizzly have in this icy habitat?
3. Diet The size of a grizzly or polar bear depends on gender, age, region, season, and diet.
Grizzly bears are omnivores, which means they will eat almost any kind of food. Their diet includes mostly plants such as wild berries, grasses, flowers, tubers, wild
vegetables, etc. They also eat bugs, rodents, and can attack larger animals, like elk or deer, for food. Grizzlies that live near coastal regions tend to be much larger as they have access to more calorie-rich food like salmon. They are one of the most adaptable bear species in the world because they can adjust to almost any kind of diet, therefore we can consider them generalists. Adult male grizzlies weigh on average 400–790 lbs., while most adult females weigh 290–400 lbs. The largest grizzly bear on record was found in Alaska and weighed in at about 1500 lbs.
Polar bears are the most carnivorous of all bears and considered specialists due to their specific dietary and habitat needs. Polar bears have evolved to use sea ice to find and feed on ice seals, specifically seal fat which is the highest calorie food source possible. Polar bears prey on both ringed and bearded seals across their range, but will take other prey like beluga whales when available. When an adult bear is in good shape, polar bears will eat only the seal’s blubber, not its meat, in order to build up the fat reserves they need to sustain themselves between meals.
In many populations, polar bears come onto land when the ice melts during the summer. On land they live off their own body fat because there are no seals, but will still eat whatever they can find. Unfortunately, terrestrial foods that polar bears eat (like snow goose eggs, berries, kelp, carrion) are less predictable and don’t provide enough calories or fat to sustain the polar bear's massive body size, let alone to add to its body fat. Adult male polar bears weigh 775 to over
1,500 pounds, while adult females weigh 330 to 650 pounds. The largest polar bear ever recorded was 2200 lbs. and was found in Alaska (1960).
a. What is the difference (in lbs.) between the largest recorded grizzly and polar bear?
b. What foods might a small adult male grizzly bear be eating; where might he live? What kind of diet might a very large adult grizzly bear be eating; where might he live?
c. Why might some adult male polar bears be much larger than others in the same region?
d. In western Hudson Bay (WHB), sea ice isn’t present for as long as it was 30 years ago, which means that polar bears now don’t have as much time to hunt seals as they used to. If WHB lost one month of sea ice, an adult female polar bear would have to eat 2350 lbs. of blueberries to offset this loss of seals, or 1670 snow goose eggs. If there are 200,000 snow goose eggs produced in this region each year and there are roughly 900 polar bears, how many eggs could each polar bear consume? Will this be enough calories to sustain each polar bear for this month? In reality do you think that the number of eggs would be divided equally? Can you brainstorm other ecological factors or issues we should consider before thinking that polar bears can use eggs as a resource?
4. Home ranges Grizzly bear habitat includes a wide range of territories. Grizzlies can be found in valleys, meadows, mountains, forests, near rivers and even coastal areas; populations gather where food sources are 2 2 abundant. Male grizzly bears have large territories, up to 4,000 km (1,500 mi ) . This land-based bear is
known for being territorial and aggressive in defending its space. The world population of grizzly bears is expected to exceed 200,000.
Polar bear habitat is sea ice, which can be unpredictable and seasonal. Their home ranges can be enormous, greater than that of any other species of bear and 300 times the size of a grizzly bear's. A large 2 2 polar bear home range can be exceed 350,000 km (135,135 mi ) , though size depends on a number of factors, including habitat quality and how much food is available. Polar bears in food-rich areas have smaller home ranges. Polar bears do not defend territories like other large carnivores. The world population of polar bears is estimated at around 25,000.
a. How many more grizzly bears are there in the world than polar bears?
b. How many grizzly bear ranges could fit into one polar bear range?
c. On the map, identify where only grizzlies live, where only polar bears live, and where these bears overlap. Does the overlap seem large compared to the entire region?
d. Can you think of two reasons why polar bears are not territorial?
5. Grolar Bears Polar bear and grizzly habitat overlaps in the western Canadian Arctic. Here, grizzlies are known to sometimes to go out on the sea ice in the spring to feed on seals killed by polar bears, and it seems like grizzly males will occasionally use this opportunity to mate with polar bear females. If they are successful, the result is a hybrid: a result of two animals of different breeds, varieties, species or genera having a baby. In naming hybrids, the father’s name comes first and, at least in the wild, we have only seen hybrids
with grizzly fathers and polar mothers, therefore we call them grolar bears. This intermixing has likely been happening for thousands of years, but may be getting slightly more common now as the warming Arctic environment is causing some animals, like the grizzly bear, to shift their range northward and other animals dependent on the sea ice, like polar bears, to spend more time near or on land.
Grizzly bears are roaming into what was traditionally thought of as polar bear habitat, such as the Canadian province of Manitoba, where they are officially listed as extirpated. In areas such as western
Hudson Bay and the Russian coast, polar bears are spending more time on land in response to climate warming and loss of sea ice, making them more likely to cross paths with a grizzly bear.
Grizzly and polar bears are the most closely related of the living bear species, so it is not too surprising that they are able to produce offspring together. It's possible that grizzly bears and polar bears may have more offspring-producing encounters in the future, but it is important to remember that mating between these species is not a widespread occurrence, and in fact these species usually prefer to avoid each other completely. We do not expect grolar bears to become a new species, or for polar bears to all turn into grolar bears (this isn’t how evolution works). We still have A LOT to learn about this hybrid, maybe you can help us!
a. Before we explain some characteristics of a grolar bear, use your current knowledge of polar bears and grizzly bears to imagine what a grolar bear might look like, eat, act like, etc. You can brainstorm with a friend or group. Draw a picture if it helps.
b. Can you think of reasons that it might be a problem or even dangerous for these species to overlap with each other? Think of what we talked about in earlier questions (hint: territoriality, aggression).
Ok, let’s take a look at what we know so far about grolar bears (scientists still have a lot to learn!).
For many species mixes, such as a mule (a mix of a horse and donkey) or liger (tiger and lion offspring), the hybrid will be sterile (i.e., unable to have babies). However, grolar bears seem to be fertile, as we know that a grolar bear female has mated with a grizzly in the wild and produced at least one cub. This is a rare and very interesting occurrence for a hybrid animal.
One wild grolar bear that was examined had thick, creamy white fur typical of polar bears, but also had the long claws, humped back, and shallow face of a grizzly bear. This animal also had brown patches around its eyes, nose, and back, and on one foot, which are all traits of grizzly bears.
Grolar bears have also been born in zoos. For example, in 2004 two grolar bear cubs were born in Germany and their physical traits were a mix of polar and grizzly bears. Their bodies were smaller than polar bears but larger than grizzlies, while their heads were in between the broader grizzly head and the leaner polar bear head. These cubs had long necks like polar bears, but small shoulder humps like grizzlies. T he soles of their feet were partially covered in hair: polar bears have hair-covered soles for insulation, while grizzlies have hairless soles.
The hybrids demonstrated behaviors that were more similar to polar bears than grizzlies. They stomped toys similar to how polar bears break ice, and hurled bags to the side similar to how polar bears sometimes hurl prey; grizzlies do not demonstrate this hurling behavior. T he hybrids were also observed lying down similar to polar bears: on their bellies with rear legs splayed.
c. We talked about adaptations in a previous question and listed ways that grizzly bears are adapted to their terrestrial environment and how polar bears are so well adapted to their own sea ice habitat. How well do you think the grolar bear is adapted to either of these environments? Do you think it has any advantages or disadvantages on land or on sea ice? Draw a habitat for which a grolar bear would be adapted.
d. Again, it is important to remember that the grolar bear is still a rare occurrence and we don’t have many specimens to study, especially in the wild. Keeping that in mind, do you think there are different versions of a grolar bear? That is, might we find a grolar bear that has a different combination of traits than the ones we currently have seen? If so, can you think of different ways that this hybrid could look or act? There are no wrong answers!
e. As climate change continues to impact the habitats of both of these species, what do you think might happen to grizzly bears, polar bears, and grolar bears in the next 100 years? Remember, grolar bears will not overtake either species or become their own species in this timeframe (or likely ever).
6. Using Technology to Study Wildlife Scientists are curious people who ask a lot of questions about the world around them! We look for meaningful patterns to help us find answers to our questions, and we can find these patterns by using the scientific method.
Make an educated guess or prediction: Hypothesis Look at or test what is happening: Observations Write down what is happening: Data Display the data in a way that helps you understand it: Graphs Decide what the data mean: Conclusions
Scientists collect data to learn more about something they are interested in. Data, which can be numbers or words, are the information gained from observing and testing an experiment. At first, data may be hard to look at because it is just a bunch of numbers and names. To organize all these numbers and names, scientists can organize it using tables or can create pictures with it using figures or graphs. By organizing the data, scientists better understand what that is happening and can make conclusions which help them get closer to the answer.
Technology has allowed wildlife science to grow by leaps and bounds. Technology helps us collect better and more complicated data, and helps us organize it in a way that allows us to draw better conclusions; therefore, we can ask better questions. Below are some examples of technology that scientists have used to learn more about polar bears.
GPS Tracking: Scientists put GPS tracking devices on animals to learn about where, when, and why they move; this information is critical for conserving species. Read more about tracking polar bears here.
Studying scent: Researchers knew that polar bears would sniff each other’s paw prints on the sea ice, and wanted to know more about why. By using the scientific method, they discovered that smelly footprints help polar bears find each other out on the vast sea ice landscape. Read the article here to find out more about the study.
Math and Modeling: Scientists can use their observations to develop models (using computers) that help us understand what is happening, and even predict future events. This video can help you understand how scientists models to help us understand the world.
DNA: Genetic material can give us an amazing amount of information about an animal’s background, its prey, its abilities, and its future. This article has just one example of how simply collecting a polar bear’s leftovers can tell us a lot about these bears and their prey.
a. Now that we talked about science and different forms of technology that help us study animals, apply what you know to grolar bears. How would you use one or more of these (or other) technologies to help us learn more about grolar bears?
7. It’s your turn to be a researcher! Imagine you are a researcher in the wild and you have stumbled across an unknown species! It is up to you to learn about what it is, what it eats, and where it moves then tell the world of your discovery.
a. Where in the world did you discover this animal? Be specific!
b. What was the animal doing when you found it?
c. Draw a picture that represents what the animal looks like and how big it is. Is it a hybrid or its own species? Give it a name that reflects something about the animal.
d. Can you list 1-3 different technologies that would help you learn more about what this animal likes to eat, where it moves, how many offspring it has, and what animals it is closely related to? e. Can you think of a technology that you could improve or invent to better learn about your animal?