Of the eight species of bears in the world, the only bears that can be said to truly migrate are Polar bears. They can travel hundreds of miles on sea ice, searching for their food source when the Artic seas start to freeze.
Other species of bears, such as the American black bear, can make seasonal migrations to areas with plentiful feed in preparation for hibernation.
More recently, researchers in Turkey discovered a group of brown bears that attempt seasonal migration between feeding and breeding sites. These are the first known brown bears to take up traveling across large distances in search of sustenance.
What Bears Migrate?
Bears are renowned for traveling in search of food, shelter, or mates. The area in which bears will generally move about is referred to as their ‘range.’ A bear’s home range needs to be extensive enough to provide for all its survival needs.
However, movement within a home range isn’t what animal experts call migration. What’s more, the size of a bear’s range can vary based on its species.
For example, giant pandas will typically have a range that extends from 3 to 7 miles. A male black bear’s range, on the other hand, can measure anywhere between 250 to 300 miles.
That means a bear’s locality and related seasonal changes play a significant role in determining how far it will travel in search of food.
This movement within the range sometimes confuses people to think bears migrate in the true sense of the word. But, the only two species of bears whose travel patterns and distance in search for sustenance are recognized as migration are polar bears and black bears.
|Type of Bear||Migration Behaviors|
|Polar Bear||North-South Migration|
|Black Bear||6-Week Autumn Migration seeking Food|
|Brown Bear||Does not migrate*|
|Grizzly Bear||Does not migrate|
|Sloth Bear||Does not migrate|
|Sun Bear||Does not migrate|
|Spectacled Bear||Does not migrate|
|Kodiak Bear||Does not migrate|
Do Black Bears Migrate?
In the case of black bears, their Autumn seasonal movement to pursue better feeding grounds is considered migration because it extends over quite a distance and they leave their home range during this period.
They will travel up to 170 kilometers away from their home range for up to 6 weeks in Autumn to find food that will sustain them for the winter. Then, they will return home to begin hibernation.
Do Polar Bears Migrate?
Polar bears migrate with the receding ice. They will migrate into icier regions in winter then retreat in summer when the ice melts.
For polar bears, movement over hundreds of miles is prompted by the fact that they live in extremely harsh conditions. Their landscape consists of sea ice that keeps shifting and changing as the weather alters.
That’s also why, much like their black bear counterparts, polar bears have widespread home ranges.
How big a polar bear’s home range is will mainly depend on the frequency of prey and sea ice quality. A polar bear can easily cover 600 to 650 miles to set up a home range away from its mother.
There’s no exact number for how vast polar bear’s range can be because tagging and tracking them is difficult.
But, scientists estimate that the species can cover a few hundred miles with ease as the sea ice expands and retreats. Researchers have tracked a female polar bear that traveled 2980 miles from Alaska to Canada and then back to Greenland, and polar bear remains have been found as far south as Sutherland in Scotland.
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Do Grizzly Bears Migrate?
Grizzlies choose to hibernate rather than migrate in the winter. They will set up a den and go into a state of torpor until the spring.
Experts state that what bears experience in winters isn’t precisely hibernation. Hibernation includes a decline in heart rate and body temperature, along with extended periods of deep sleep.
When bears huddle down in their dens for the winter, they only experience two things: deep sleep and a decline in heart rate. Their body temperatures only drop slightly from what their summer temperatures are.
But let’s leave that for now and focus on whether Grizzlies hibernate or migrate in winter.
Grizzly bears can travel 60 or so miles searching for food, but they do not migrate out of their home range. Instead, like black bears, grizzlies start chowing down on protein and fat during the summer months to be able to get in shape for hibernation.
And even though, according to science, grizzlies do not truly hibernate, they still undergo some unbelievable changes during their long winter nap. For instance, a grizzly’s heart rate can drop from 50 beats per minute to 19 beats per minute.
Moreover, grizzlies can also lose about 30% of their body weight during hibernation without experiencing any bone or muscle loss. So, when spring is around the corner and the grizzly emerges from its den, it’s none the worse for wear but most definitely a little hungry.
Why Do Some Bears Migrate?
Migration isn’t new or uncommon in the animal world. Many species travel across great distances to find more favorable living and feeding conditions as the seasons change and winter makes food sources scarce.
Bears that migrate, such as polar bears and black bears, do so because of the scarcity of food sources, changing landscape conditions, or both.
The survival instinct of all animals, including bears, is truly incredible because it kicks into gear even before the food sources start dwindling.
Black bears start their seasonal migrations sometime in August to ensure they’re ready to begin hibernation by the time fall rolls around. The species can start hibernation in September to avoid fall-related food scarcity and stay in their dens for a maximum of 7 months until April.
Since polar bears spend a sizable amount of their lives on sea ice, they don’t have much choice in terms of migration. In summer, the sea ice tends to retreat because of high temperatures. In contrast, the sea ice expands during the fall and gives the bears an advantage over the seals when hunting.
Read Also: Do Grizzly Bears Track Prey?
Migration can be a bit of a tricky concept to grasp when it comes to bears. Primarily, that’s because bears spend their time moving about their home range in search of food, shelter, or mates. They’re certainly not stationary animals, but neither do all of them migrate.
Experts agree that the two bear species that can be said to definitively migrate are black bears and polar bears. However, unlike polar bears, black bears tend to make seasonal migration to get ready for hibernation for six to seven months.
That makes polar bears the only bear species that travel hundreds of miles in search of a better food source in rapidly changing landscapes due to the climate – making them true migratory animals.
Brown bears have also contributed to the migration mystery of bears recently. A group of brown bears in that region was observed migrating between breeding and feeding sights, which has led some scientists to conclude that human-related division of bear habitat can directly affect their lifestyle.
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