ABC Islands bear facts for kids
Quick facts for kids ABC Islands bear |
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Ursus
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U. a. sitkensis
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| Ursus arctos sitkensis Merriam, 1896
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The ABC Islands bear, also known as the Sitka brown bear, is a special type of brown bear. It lives in Southeast Alaska on three islands: Admiralty Island, Baranof Island, and Chichagof Island. These islands are often called the ABC Islands and are part of the Alexander Archipelago.
What makes these bears unique is their genes! They are related to both brown bears and polar bears. Their home is inside the Tongass National Forest, which is a very wet rainforest.
Contents
What They Look Like
ABC Islands bears look a lot like other brown bears from Alaska. They have fur that is usually the color of milk chocolate, but it can also be blonde or even black. They have a noticeable hump on their back and a slightly curved face. Their front claws are long.
Adult male bears usually weigh between 195 and 390 kilograms (about 430 to 860 pounds). Adult females are smaller, weighing around 95 to 205 kilograms (about 210 to 450 pounds). When standing on all fours, they are typically 90 to 110 centimeters (about 35 to 43 inches) tall at the shoulder.
Where They Live
These bears live in the Tongass National Forest. This means they rely on the plants and animals found in this forest. Two common trees in their habitat are the Sitka spruce and the Western hemlock.
What They Eat
ABC Islands bears eat a variety of foods that grow or live in their area.
- Plants: They munch on grasses, plant bulbs, and berries like salmonberries and blueberries. They also eat mushrooms.
- Animals: Their diet includes small animals like voles, mice, and squirrels. They also love to eat salmon.
How They Behave
ABC Islands bears usually prefer to be alone. However, if there's a lot of food in one spot, you might see several bears together.
Female bears are ready to have cubs when they are about four to seven years old. Mating happens between May and July.
These bears hibernate for the winter. They usually go into their dens in October and come out by April, or sometimes as late as June. Pregnant females give birth to their cubs in the den during January or February. They typically have two or three cubs at a time. The cubs stay with their mother for up to three years. During this time, the mother bear won't get pregnant again.
Their Link to Polar Bears
Even though ABC Islands bears look and act like typical brown bears, they have a special genetic connection to polar bears. Their mitochondrial DNA (a type of genetic material passed down from the mother) is actually more similar to polar bears than to other brown bears!
Studies on Their Unique Genes
Scientists have done several studies to understand this unique link.
1996 Study
A study in 1996 looked at brown bears in Alaska. It found that bears on Admiralty Island didn't seem to mix with bears from other islands or the mainland. Scientists thought this was because strong ocean currents made it hard for bears to swim between land masses. This study also suggested that during the last Ice Age, when much of the coast was covered in ice, these bears might have lived only on the ABC Islands.
2011 Study
In 2011, another study used the ABC Islands bear population to learn more about how polar bears and brown bears might have mixed in the past. It showed that polar bears were likely present on the ABC Islands during the last Ice Age.
2012 Study
An international study in 2012 suggested that polar bears and brown bears separated into different species about 4 to 5 million years ago, possibly due to climate changes like ice ages. However, they found that brown bears and polar bears have interbred (had cubs together) again more recently, about 160,000 years ago. This study found even more genetic similarities between polar bears and the ABC Islands brown bears. This means studying these bears helps us understand how polar bears evolved!
2013 Study
Research in 2013 suggested that about 6.5% of the ABC Islands bears' X chromosomes (a type of genetic material) came from polar bears. This study believes that the ABC Islands bears descended from polar bears who got stuck in Southeast Alaska after the last Ice Age when the ice melted. Then, male brown bears swam to the islands and mated with the female polar bears. Over time, the bears on the islands started to look and act more like brown bears, even though they still carried some polar bear genes. This shows that sometimes, when an isolated group of animals meets a new species they can breed with, their genes can change a lot.
Scientists found that polar bears don't seem to have brown bear genes, but ABC Islands bears clearly have polar bear genes. Fossils from the last Ice Age show that there wasn't much habitat for brown bears in this area, but there were many marine mammals like seals, which are a favorite food of polar bears.
Threats to These Bears
One big problem for ABC Islands bears is conflict with humans. This can happen if bears come into towns or if they encounter hunters. Climate change is another possible threat. As these bears show, changes in climate can affect animal species in important ways.
See also
In Spanish: Oso pardo de Sitka para niños
