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Bear Foraging on Fruit II.

The main problem that confronts bears in their pursuit of fruit is getting them off the bushes either before other competitors get there or before the fruits decompose.  After finding a suitable patch, a bear may face more immediate problems such as gaining access to fruit elevated above the ground, gleaning fruits from out of a less digestible matrix of leaves and twigs, or simply the rate at which it can consume and digest readily accessible berries.  But ursids are as well equipped as any organism to deal with these difficulties and draw upon an acute sense of smell, relatively well-developed color vision, facile lips, paws, and tongue, and varied climbing capabilities to ingest sometimes phenomenal amounts, 10-45 kg, of energy-rich fruit in a given day.

The simplest foraging scenario for a bear eating fruit is probably the removal of berries from ground-hugging or nose-level bushes.  In this case the bear often tries to maximize the number of berries ingested relative to leaves and twigs.  This endeavor is obviously limited by energetic considerations and, at some point, it is not worth the extra time and effort to be picky.  However, this break-even point clearly varies among individual bears (depending upon their skills and tolerances) and with the abundance and type of berry being consumed.  Although it has not been clearly demonstrated, there are observations supporting the logical expectation that bears are more selective when sated or when foraging upon large abundant berries.  Observers have thus reported behavior ranging from the sloppy to the fastidious.  Some bears wrap their lips around a stem and indiscriminately strip off leaves, twigs, and berries.  Other bears daintily pluck berries out from among less desired portions by a combination of lip and tongue work, sometimes aided by manipulation of stems with their paws.  Accordingly, we find berry feces that sometimes contain nothing but the remains of fruits and others that contain mostly leaves.

Numerous berries are produced towards the top of tall bushes.  Mountain ash, elderberry, chokecherry, and hawthorn are good examples of this type of fruit that is potentially quite abundant but often beyond immediate reach of tongue and lips.  Bears resolve this problem quite simply by squatting or standing on their hind legs and pulling more flexible fruit-laden stems to within range of their mouth.  More robust stems may be subdued by either grabbing them with the paws and pulling on them until they break or walking along them from proximal to distal end until either the branch breaks or the fruit is reached.

Bears employ variations on this technique to get fruit out of trees.  There are many incentives to make a trip into the tree tops, including potential meals of sugar-rich cherries that would otherwise have to wait until later in the year, or be sacrificed altogether to competing rodents and birds.  The option of arboreal foraging is largely denied to grizzly and brown bears, and is perhaps the price they pay for being able to live in austere northern habitats where digging and large body size are important to survival.  This not to say that grizzlies never climb trees, and, in fact, some closely-related European brown bears have been observed to forage for fruits or leaves in tree canopies in Norway, the Alps, and Afghanistan.  Nevertheless, tree foraging is the definitive domain of the smaller-bodied black bear, whether in North America or Asia.

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