Hyperphagia Bears – Fat and Dangerous?

During the late summer and fall months of the year, bears eat as much as they possibly can in preparation for the lean months ahead and their long winter nap of hibernation. This period of intense, virtually nonstop eating is known as hyperphagia. During this time bears ignore the usual biological cues that would normally tell that they’re full, and instead, they just keep on eating, and eating, and eating…gaining an enormous amount of extra weight!

A Kodiak bear in full hyperphagia mode!

Bear Safety During Hyperphagia

While one should always make it a point to be safe and respectful in bear country and make sure bears are not attracted to your food sources, it’s especially important to do so during this time of hyperphagia, as bears can become very aggressive and temperamental in situations that involve a potential meal, or, anything that would be a threat to what a bear perceives as a potential meal.

While bear attacks are quite rare in the grand scheme of things, the number of attacks can be much higher during the fall months when bears turn into relentless eating machines. Fishermen and hunters can especially get into trouble as bears are commonly after the same food sources and are generally in the same areas. So again, one needs to be extra cautious when in bear country at this time of year.

Eating Habits During Hyperphagia

Bears such as the huge Kodiak and coastal brown bears of the mainland of Alaska can eat up to almost 100 pounds of food a day during this time of hyperphagia, and as a result, they can get very, very fat! In fact, Katmai National Park has a Fat Bear Week Contest every autumn to celebrate this time of year when the bears pack on the pounds to extreme measures.

Katmai National Park Fat Bear Week
The winner of the 2019 Katmai National Park Fat Bear Week. (Photo Credit: Katmai National Park)

Bears can be rather picky eaters earlier in the summer when food is abundant. For example, brown bears who feast on salmon will often only eat the tasty, high-fat portions of the fish such as the brains, skin, and eggs, and disregard the rest. However, later in the summer and fall, when the salmon runs are finishing up, bears will eat everything, and even readily scarf down the nasty, old, rotting fish carcasses that collect along the banks of rivers. In locations or during years where natural food sources are scarce, bears sometimes head to urban areas in search of food such as trash, and as a result, they get into all kinds of trouble.

hyperphagia Kodiak bear eating trash
A Kodiak bear during hyperphagia eating trash in a suburban area.

Once they’re good and fattened up, the bears head to their winter dens, typically in late October, and slumber away all those extra calories, only to emerge in May or June and do it all over again.

The Adventures of King Kodiak, The Biggest Brown Bear in the World, Joseph Classen
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