By Christine Fenwick, Bear Manager
Fortress of the Bear
PO Box 2337, Sitka, AK 99835
oso.ursa@yahoo.com

<strong>Abstract</strong>
<em>Behaviors were closely monitored for two, two-year old, male brown bear (Ursus arctos) cubs at Fortress of the Bear in Sitka, Alaska during the fall, winter, and spring of 2008 and 2009.  Denning behaviors became evident in early November with changes in food consumption, and activity periods.  Food consumption decreased from 14,000 kilocalories per day per bear in September to 4,100 kilocalories per day per bear in November.  Killisnoo and Chaik weighed 200 and 225 kilograms respectively in September.   Daylight hours and daily temperatures decreased in November; however the fall was atypically warm by two to seven degrees Celsius.  Diet consumption reached a low of 1,696 kilocalories per day per bear in late December.    Each bear exhibited its own unique behavioral response to the changes in the captive environment.  Keeper routines changed in response to changes in bear behavior.  Visitor attendance decreased, and other disturbances were also reduced.  In the deepest part of winter, the bears were still eating, defecating, and urinating.  The cubs had decreased activity for parts of the day, and were spending 18 to 20 hours in the den. Food consumption and activity levels returned to normal with the increase in daylight hours and temperatures of March and April.  Most influential on their behavior, was the dynamic relationship between the two cubs.  Although allowed to feed to satiation during the hyperphagia stage of late summer, they may not have had enough fat on them for winter denning.  As cubs, their bodies continued to grow through the winter as they lost fat and gained length and height, emerging from the den 1.5cm taller than when they entered.  There were also uncontrollable outside disturbances, and there may have been other factors affecting their denning behavior.  The bears were fed according to their consumptive needs, given denning space and denning material.</em>

Behavior-based husbandry utilizes the natural history of an animal to determine the appropriate husbandry practices to best meet their needs.  For brown bears and black bears, there are seasonal changes that affect their behaviors, most notably during the winter, which is naturally a time of denning.  In wild bears that have a sufficient fat layer to allow winter denning, there are three main behavioral cues of winter denning:  1. Decreased food and water consumption, often times ceasing to eat and drink completely; 2. Decreased activity, often spending more time near the den site as winter approaches;  and 3.  Entering a den and remaining in the den for prolonged periods of time, some bears will enter a winter den and remain there for up to six months in the far north (Brown, 2009).   Winter denning is a complex biological and biochemical process influenced by many variables that include, but are not limited to:  acquisition of a sufficient fat layer to survive a winter without food, decreased daylight hours, decreased average daily temperatures, and an appropriate denning site and denning materials.   When all of the factors are present, they produce predictable winter denning behaviors.   These factors are variable and are necessary to meet the changing environment from year to year as winters will differ.  In captive communities, keepers are tasked with making decisions for the animals in their care to best meet the needs of those animals and the management needs of the facility.  Often times keepers are required to maintain protocols that do not allow the animals to choose what is best for themselves.  For winter denning in bears, many factors must align for denning to occur, and no one knows better than the bears themselves if all those factors are in line (Poulsen, 2008).  The onset of winter is a time of reduced food abundance, and food reduction for denning should follow the bears’ cues.

<img class="alignleft size-full wp-image-808" title="bear-in-snow" src="http://aecetia.net/gws/aazk/wp-content/uploads/bear-in-snow.jpg" alt="bear-in-snow" width="288" height="216" />

<strong>Killisnoo Bear showing increasing lethargy by
resting on a log in the exhibit in January 2009.
(Photo by Christine Fenwick)</strong>

Fortress of the Bear is home to two male, brother, brown bear cubs, Killisnoo and Chaik, who turned two in the winter of 2008-2009.  The exhibit has full exposure to the elements, and the bears are exposed to year-round weather patterns, vegetation changes, and temperature changes.  The den is completely enclosed providing a private, quiet, dark, and dry space.  The den is not temperature controlled, and its temperature is roughly the same as the ambient temperature.  The bears were observed closely throughout the year to identify behavior patterns, and husbandry protocols were modified based on the behavioral cues from the bears.

The bears’ behaviors were closely monitored on a daily basis, with observations logged in the daily paperwork.  Keepers watched for:  aggressive behavior, play behaviors, general activity levels, food consumption, and weight fluctuations.   In the fall and winter, behaviors were monitored for denning specific cues that would indicate a change in husbandry.  Denning behavior cues included:  decreased activity levels, decreased play behavior, increased nest building behavior, increased time within the den, and decreased food consumption.  Decreases in behaviors were determined based on a comparison to summer behaviors exhibited by the bears.  Husbandry changed as bear behavior changed.  Average temperatures, daylight hours, and precipitation were recorded for each month.  Kilocalorie content of the diet was figured using averages for kilocalorie content of foods normally fed.  All food is donated, so the types of produce, dog food brand, and meat sources were highly variable.  Average kilocalorie content for food was broken down into produce, dog food, and meat.  With kilocalorie content of all types of produce averaged, all types of possible dog food brands averaged, and all types of meat sources averaged.  Daily nutritional logs were kept to track the diet levels.  Diets consisted of dog food, produce, and meat fed in a 1:1:2 ratio respectively.  Diets were decreased in the fall based on cues from the bears, and kilocalorie content of diet changes was logged.  No supplements were given, and enrichment food was counted as part of the overall diet and calculated into their overall kilocalorie intake.

August and September were months of hyperphagia for the bears, and they consumed 14,022 kilocalories per day.  August and September had 16 and 12.5 hours of daylight respectively, and temperatures were 10ºC [50°F].  Due to security concerns the bears were locked within a secure night holding area every night.  They were released into the exhibit at 0730 in the morning, and brought back in for the night at 1930.  The night holding area was set up with extensive enrichment every night to allow them the option to play and interact if they chose to.    They were most active in………