Bears as Predators ~

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Hunting Techniques.
When searching for prey, grizzlies primarily rely on their acute sense of smell by bowing their heads low to the ground and sniffing while they walk.  They also capitalize on their sight and hearing by periodically standing on their hind legs to gain a better view of their surroundings as well as hear further.  While standing, they turn their head and ears in various directions to scan the area.  Most of the time, a bear will not know where a herd of ungulates is located and can spend up to several hours conducting a search.  Grizzlies are usually searching for calves that are lying down and sleeping, or bedding calves, as these are the easiest to catch.  When a herd is located, the bear will pace around a 200 m radius where the herd was just previously standing in hopes of finding a bedding calf.  While doing this, the bear will avoid being seen by the herd.

Army cutworm moths, Euxoa auxiliaris, are an important food source for some grizzly populations. Image © Whitney Cranshaw
When a bedding calf cannot be found, a grizzly can resort to a chase or an ambush to catch its prey.  The bear will stalk a herd closely while remaining unseen, and suddenly attack with a burst of speed.  They will focus on straggling calves that lag behind the herd and have little protection from adults.  When the bear closes in on its prey it can knock it over with its muzzle or paw, and will usually begin eating the abdomen of the calf to quickly kill the victim.  Grizzlies have been seen waiting on the edges of forests near fields and meadows for herds to enter where they can easily ambush their prey.
Large numbers of grizzly bears on the Absaroca Mountains in Yellowstone National Park rely heavily on army cutworm moths (Euxoa auxiliaris) as a main source of nutrition during the months of late June to mid September (French et al, 1994).  Large numbers of moths arrive here during flowering season, and during the day take shelter under large rocks covering the side of the mountain.  After locating a cluster of moths by their scent, the bears move rocks, dig and excavate until they find the moths.  Although bears are found in large groups here, there is little social tension as plenty of food reduces the need for competition.  Moth eating Grizzlies have also been found on Talus slopes in the Mission Mountains of Montana and in Glacier National Park. Reply