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Polar Bears International and Discovery Educator Network Math Challenge
CRACKING THE CURIOUS CASE OF THE GROLAR BEAR: Teacher's Notes
1. Animal Birth Weights
a. Just based on the above birth weight ratios, who might have the easier time giving birth:
Elephants or humans? Elephants
b. Bears have the smallest infant:mother ratio of any placental mammal! Baby bears are
very 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 pounds when she gave birth to her
two cubs. Her first cub was only 0.19 lbs. So, 0.19/0.19 : 238/0.19 = 1:1256! This mom
was 1256 times larger than her first cub! Mei Xiang’s second cub was 0.30 lbs. How
many times larger was Mei Xiang compared her second cub? 783.
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 lb when she gives birth to a 1 b cub, what is the baby:mom birth weight ratio? 1:300
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 one and three cubs every 3 years. If a polar bear
female first reproduces at 5 years old, gives birth to two cubs every 3 years, and lives
until she is 24, how many cubs will she have had in her lifetime? 14 (2 cubs at each age
of 5, 8, 11, 14, 17, 20, and 23 = 2 X 7 = 14)
2. Adaptations
a. Thinking of adaptations, what advantage do grizzly bears have in being brown, and polar
bears have in being white? Camouflage in their own habitats for hunting prey
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? Dense and hollow
fur, and thick layer of fat. Also: furred paws, short tail to prevent heat loss, black skin
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? It would likely have a hard time. Advantages are that it is
strong and could maybe use its strength to break through ice to find food or threaten
polar bears to steal their food. However, disadvantages include that it would get cold, its
brown fur would stand out against the ice making it hard to sneak up on seals, its claws
aren’t well suited to hooking marine prey, etc. There are many other answers here that
kids may come up with! There would be few wrong answers.
3. Diet
a. What is the difference (in lbs) between the largest recorded grizzly and polar bear?
2200 – 1500 = 700 lbs
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? Small
grizzly- likely lives in a tundra area, or some sort of strictly terrestrial region. He is likely
eating a lot of berries, vegetation, and little protein/fat- low calorie diet. Large grizzly=
likely living in a coastal area and has access to a lot of salmon and other fatty marine
foods- high calorie diet.
c. Why might some adult male polar bears be much larger than others in the same region?
Genetics, level of experience hunting or finding food, chance, disease, specific age (if
young adult, the bear might be inexperienced finding food; if very old adult, the bear may
be worn down and too old to eat enough).
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 offset the loss of seals 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? If
divided equally, each bear would receive about 222 eggs which is not enough to offset
the loss of seals. In reality, the eggs would not be equally distributed. We can consider
many factors when deciding whether eggs would be divided equally, including that some
bears will learn to find eggs while others simply won’t; some bears may enjoy eggs more
than others do. Also, not all bears are even in the same region where snow geese are
laying eggs. Snow geese populations are going to be hit hard by polar bear predation,
and the number of eggs produced may drop over time if there are fewer geese hatched
to lay eggs. Furthermore, other animals eat snow goose eggs; these animals might be
negatively impacted if they now have to compete with polar bears for eggs.
4. Home ranges
a. How many more grizzly bears are there in the world than polar bears? 200,000 - 25,000
= 175,000
b. How many grizzly bear ranges could fit into one polar bear range? 350,000/4000 = 87.5
grizzly bear ranges could fit into 1 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?No,
overlap between the species is comparatively small.
d. Can you think of two reasons why polar bears are not territorial? Unpredictable/seasonal
habitat and territories are simply too large to be able to defend
5. Grolar Bears
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. Up to teacher
whether to draw a picture or just discuss in groups or class- any combination of the traits
mentioned so far would be possible, no real wrong answers.
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. Grizzly
bears are quite territorial and aggressive and can outcompete polar bears for food (i.e., a
grizzly will push a polar bear off a seal the polar bear caught). These bears will also eat
each other if the chance arises (unclear whether they actively hunt each other but they
do at least feed on each other’s carcasses) and grizzlies at least will kill and eat polar
bear cubs.
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? Where
might a grolar bear be finding its food? Do you think it would have trouble finding a
mate? Draw a habitat that a grolar bear would be well adapted for. Not very well suited
to either habitat, but maybe could make a living along the coast of the Beaufort Sea
where it could exploit land foods but also some marine foods when the sea ice freezes in
the winter. It might depend on how well and where the grolar bear was taught to hunt by
its mom. Advantages and disadvantages would be in line with the adaptations
mentioned in previous questions, kids can come up with a variety of answers. Also, for a
habitat they could do an intermediate land/marine habitat, or make up an imaginary one
that suits the grolar, up to the teacher.
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! As long as the answers fit within the ecological and biological knowledge we
have of polar bears and grizzlies, no answer is wrong. Accuracy or genetic details will
depend on grade level and knowledge of genetics. It is possible there could be a wide
range of genetic combinations that would form a grolar bear.
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). Grizzly bears will likely move into new habitats
and farther north. We expect grizzlies will likely hibernate in polar bear maternity denning
habitat and could come out of hibernation at the same time and potentially kill polar
cubs. Polar bears may shifting their range into regions where sea ice is hanging on and
will spend more time on land. They may be outcompeted for food sources by the grizzly.
It is possible that grolar bears will become more common, though this may not give any
advantage as the grolar isn’t well adapted to any specific habitat.
6. Using Technology to Study Wildlife
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 you learn more about grolar bears? Wide variety of
answers, but we expect things in the vein of collaring grolar bears to see where and
when they move and guess at what they are eating, using techniques and results of the
scent communication study to learn how grolar bears find each other in the wild and who
they are mating (grizzlies? polars?), using math and modelling to take what we know
about grolars and put it into a computer model that will help us understand how the
grolar bear fits into the food web and other such questions, and using DNA to better
understand this animal and its parents, offspring, and characteristics.
7. It’s your turn to be a researcher!
It is up to teachers how realistic or fantastical kids are allowed to get for a-c.
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 different technologies that you would learn more about this
animal like what it eats, where it moves, how many offspring it has, and what animals is
it closely related to? From technologies listed or other ones the students have
researched
e. Can you think of a technology that you could improve or invent to better learn about your
animal? Use their creativity to come up with something new or improve something
current