The Kodiak bear (Ursus arctos middendorffi), also referred to as the Kodiak brown bear or Alaskan brown bear, inhabits the islands of the Kodiak Archipelago in southwest Alaska. These bears are the largest brown bear subspecies and are comparable in size to polar bears. The Kodiak bear's diet is a fascinating blend of opportunistic feeding habits, seasonal adaptations, and a keen ability to exploit the rich resources of their environment.
Kodiak Bears: Size and General Characteristics
Physiologically, the Kodiak bear is very similar to other brown bear subspecies, such as the mainland grizzly bear (Ursus arctos horribilis) and the extinct California grizzly bear (U. a. californicus). The main difference is size, as Kodiak bears are on average 1.5 to 2 times larger than their cousins. While most brown bears usually weigh between 115 and 360 kg (254 and 794 lb), the Kodiak bear commonly reaches sizes of 300 to 600 kg (660 to 1,320 lb) and can even exceed 680 kg (1,500 lb).
Hair colors range from pale blonde to orange (typically females or bears from southern parts of the archipelago) to dark brown. Cubs will often retain a white "natal ring" around their neck for the first few years of life. The size range for females (sows) is from 181 to 318 kg (399 to 701 lb), and for males (boars), it is 272 to 635 kg (600 to 1,400 lb). Mature males average 477-534 kg (1,052-1,177 lb) over the course of the year, and can weigh up to 680 kg (1,500 lb) at peak times. Females are typically about 20% smaller and 30% lighter than males, and adult sizes are attained when they are six years old. Bears weigh the least when they emerge from their dens in the spring, and can increase their weight by 20-30% during late summer and autumn. An average adult male measures 244 cm (8 ft 0 in) in length, and stands 133 cm (4 ft 4 in) tall at the shoulder. The largest recorded wild male weighed 751 kg (1,656 lb), and had a hind foot measurement of 46 cm (18 in). A large male Kodiak bear stands up to 1.5 m (4.9 ft) tall at the shoulder when it is standing on all four legs. When standing fully upright on its hind legs, a large male could reach a height of 3 m (9.8 ft).
The standard method of evaluating the size of bears is by measuring their skulls. Most North American hunting organizations and management agencies use calipers to measure the length of the skull (back of sagittal crest on the back of the skull to the front tooth), and the width (maximum width between the zygomatic arches - "cheek bones"). The total skull size is the sum of these two measurements. The largest bear ever killed in North America was from Kodiak Island, with a total skull size of 78.1 cm (30.7 in), and eight of the top 10 brown bears listed in the Boone and Crockett record book are from Kodiak. This brown bear population only occurs on the islands of the Kodiak Archipelago (Kodiak, Afognak, Shuyak, Raspberry, Uganik, Sitkalidak, and adjacent islands). The Kodiak bear population was estimated to include 3,526 bears in 2005, yielding an estimated archipelago-wide population density of 270 bears per 1000 km2 (700 per 1000 sq.mi).
Seasonal Eating Habits
Alaska’s bears have just six months to eat a year’s worth of food, so they must work hard over the summer and fall to get in supersized shape. In their winter torpor, a deep sleep similar to hibernation, they will not eat, drink, or release any bodily waste for several months. Bears enter a stage called hyperphagia as they prepare to den. During this time, they have an insatiable desire to eat and drink and focus most of their attention on obtaining food. The next several months of famine in the den will ultimately balance out the weight they gained in summer and fall. Adult male coastal brown bears may eat around 80-90 pounds of food and gain six pounds per day.
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Spring
Emerging vegetation and animals that died during the winter are the first foods bears eat in the spring. This allows the bear to quickly replace the weight that was lost during hibernation. Green plants like sedges, grasses, cow parsnip, and fireweed shoots are especially key in the early summer when bears have recently emerged from winter dens and other foods are scarce. Brown bears use their powerful shoulder muscles and long claws to dig for plant roots and bulbs.
Summer
As summer progresses, a wide variety of vegetation supplies nutritional needs until salmon return. Salmon runs extend from May through September on most of the archipelago and bears consume the five species of Pacific salmon that spawn in local streams and lakes. During the peak of salmon runs, an adult male brown bear in Kodiak National Wildlife Refuge may eat around 30 salmon a day! As their stomachs fill with fishy goodness, bears tend to high-grade their bites. Fish heads, skin, and eggs have a particularly high fat and protein content. Choosy chompers eat the best bits first and leave the rest to scavengers. Brains are a dense source of energy for bears intent on getting the most calories for their mouthfuls.
Fall
In the late summer and early fall, bears consume several types of berries when they reach their ripest point and have the highest levels of sugar. Alaska has a bounty of wild berries, and coastal brown bears collect them all: salmonberry, blueberry, and elderberry to name a few. A good way to know when berries have hit peak season? Piles of bear scat will be full of berry seeds! Most berries are rich in sugars, a carbohydrate that helps bears with their weight gain goals when combined with their salmon protein buffet. Elderberries bring a unique superpower to the table: they have substantially more protein than most other berries and make a favorite bear treat. Plus the large clumps of berries on an elderberry shrub mean easier harvesting and less energy expended - win!
As climate change causes elderberries to ripen earlier, berry season is now overlapping with salmon season and some bears are abandoning salmon runs to focus on the berries.
Year-Round
Bears also feed on wind-rowed seaweed and invertebrates on some beaches throughout the year. Bears that live along the coast benefit from a supplemental seafood surf and turf menu, scraping invertebrates from the rocky beaches, digging for clams in mudflats, and feasting on the occasional whale carcass washed ashore - the stinkier, the better.
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The Importance of Salmon
Salmon are a not-so-secret ingredient to the massive size of coastal brown bears in Alaska. Alaska Peninsula National Wildlife Refuge habitat supports nearly 40% of the Bristol Bay sockeye salmon run, the largest sustainable sockeye fishery in the world. The refuge also supports a healthy population of large coastal brown bears!
A Balanced Diet
As true omnivores, brown bears take advantage of seasonal abundance and time their servings with peak nutritional value and opportunity. Their final flab figure before denning may be hundreds of pounds more than their starting weight in early summer.
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