Long Distance Movements by Female Bears

By Walter McCown

FWRI bear researchers began efforts to develop a demographic profile of bears in the Apalachicola subpopulation in May 2016.  We have, thus far, placed Iridium satellite collars on 37 adult female bears to document survival rates, the age of first reproduction, the number of cubs produced, and the interval between litters.  Additionally, each spring we place VHF collars on cubs in the den and monitor them several times a week to document their survival rate.  While these demographic profiles will enable us to construct a population model useful for the management of this subpopulation of bears, the presence of a satellite collar programmed to acquire locations every two hours affords us interesting insights into these bears.

One intriguing aspect of bear behavior occurs during the fall when bears increase their normal food intake from about 8,000 calories (kcal) per day to approximately 20,000 calories per day, resulting in an increase of their body weight by approximately 1.5 kg per day.  This behavior, known as hyperphagia, creates stores of energy in the form of fat and is an adaptation by bears to the lack of food during the winter.  Because bear foods are normally isolated in time and by space, bears may wander widely in the fall and spend up to 20 hours per day eating.  Although the list of food items consumed by Florida bears is rather lengthy (over 100 items) and diverse (bromeliads to walking sticks), acorns and palmetto berries are dominant fall food items in most subpopulations.  When these food items are abundant bears do well and have smaller home ranges.  When these items are more scarce, bears must make greater movements to obtain the calories necessary to survive the winter.

In fall 2016 we noted movements of several bears of 20-30 km into remnants of coastal scrub habitat where they fed on acorns.  In fall 2017, when acorns were apparently not as abundant, bears moved similar distances but further inland to forage in stands of hardwoods along area creeks and rivers.

Interestingly, in fall 2017, bear F605 moved from her home range in Tate’s Hell State Forest near Carrabelle, to private land near Hosford, Florida.  This 12-year-old female accomplished this trek of approximately 58 km (as the crow flies) with her three 8-month-old cubs in only three days (see top photo).  Subsequently, she remained near Hosford all winter, did not make any more noteworthy movements, and successfully raised all three cubs (see map below).

Locations of female bear F605 and three cubs October 17-19, 2017 (click to enlarge).

Bear researchers are frequently impressed with how black bears adapt to their environment and changing conditions.  However, we are bewildered with their ability to somehow know that conditions in distant locations are superior to those in their current use area.  Yet, it is abundantly apparent they do know.  In previous studies, Florida researchers noted lengthy fall movements by bears in Big Cypress during an apparent palmetto berry failure and in Ocala when a drought caused both oak and palmetto fruit production to fail.  Nonetheless, the trek by F605 that we documented was an impressive one for a female with three cubs.