Wednesday, June 30, 2010

The Babes Of Summer: Black Bear Cubs

One of nature's grandest spectacles in the Summer is the sight of small Black Bear cubs as they wrestle and climb and play. These activities help develop the skills they will need to survive.

Cub survival is also influenced by food abundance and quality, physical condition of the mother, social factors, litter size, experience of the mother, and cub birth weight. Mothers who are nutritionally stressed, or first-time breeders, are more likely to lose cubs than are well-fed mothers. Usually, litter order is the principal factor in determining minimum first-year survival. Many first litters had 0% cub survival through one year, while nearly half of second and later litters have 100% survival through the first year. Since most first litters are born to 3-year-old sows, it is likely that mothers fail to attain the minimum weight necessary to successfully raise cubs.

Litter size ranges from 1 to 4 young, first litters may be small, usually a single cub. Two or 3 cubs are typical thereafter. Five-cub litters are uncommon; extraordinary litters of 6 cubs have been reported in Manitoba and Pennsylvania. The sex ratio at birth is usually 1:1. However, the sex of cubs is related to the mother's weight and to litter size. The number of males is usually higher with heavier mothers, but lower as litter size increases.

Young black bears remain with their mother until about 16 to 17 months of age. Family breakup (typically in June) is initiated by the mother when she comes into estrus. She probably uses threats or aggression to compel the young to disperse. However, the female often tolerates the presence of her independent offspring within her home range and will avoid the area used by her daughters. Mothers recognize their own daughters and respond to them on that basis. Male yearlings typically disperse from their natal area after a year or so.

Did you know? During the denning period, sows may produce more than 50 lbs. of milk, metabolized from body fat. This milk is rich in fat and protein and nearly twice as high in kilocalories than either human or cow milk. Cubs may weigh up to 9 pounds by the time they leave the den.

Cubs learn to climb at an early age and their mother sends them up trees
while she feeds, or when danger may be present.

 A sow with her two small romping cubs
View a better quality version of this video at my Web site.

For more black bear photos, information and video clips, visit the black bears section of my Web site.

This month's blog is dedicated to my wonderful, loving Grandmother, who was the cornerstone of my entire life. I lost her on Thursday morning, June 3rd, 2010. She was actually a mother to me, as she and my grandfather raised my brother and I, in fact we called her 'Mom' all of our lives. She always loved seeing my photos and video clips of the young, wild animals - particularly the bear cubs and whitetail fawns. May you rest in peace, someday we shall be together once again. I miss you, and I love you Mom.