Readers should note the productivity data presented is from bears harvested in 2001.  Information from reproductive tracts obtained in 2002 cannot be fully analyzed until ages of sows are determined, which is usually in September.

 

A total of 69 reproductive tracts were collected in 2001.  Three were of limited use because part of the tract was missing or bear age was not determined.  Twenty-two (32%) of 69 tracts showed no evidence of breeding; the majority of these were yearlings and two-year-old bears.  Twenty-five (36%) reproductive tracts revealed breeding had occurred in 2001 with birthing expected in early 2002.  The remaining 22 tracts (32%) showed that sows had given birth in early 2001.  Their cubs were either lost during the year or they were still being raised when their mothers were killed.

 

All yearlings (10) showed no evidence of breeding, which is expected in this age category.  We have noted over the years that only about half the two-year-olds breed for the first time—this also occurred in 2001, as nine of 18 reproductive tracts of two-year-old sows revealed they had not successfully bred.  Of the nine that had been bred, one sow had one corpora lutea (evidence of one egg fertilized), five showed two corpora lutea (twins), and two contained three corpora lutea (triplets).  One sow had three corpora lutea and three distinct embryos, but one embryo was being reabsorbed, resulting in the potential production of twins.  The resultant production rate for pregnant two-year-olds in 2001 averaged 2.1 cubs per sow.

 

Of 11 three-year-old sows, three (27%) were probably first time breeders, all with twins.  Eight (73%) in this age group had produced cubs as two-year-olds:  six bore twins, one gave birth to triplets, and one had birthed a single cub.  This would produce an average of 2.0 cubs per breeding three-year-olds.

 

Of bears four years and older, three (10%) of 29 tracts showed no evidence of breeding.  Two of these bears were five years in age and one was a 22-year-old sow.  Twelve (41%) of the older age tracts showed they had bred in 2001 and would have probably given birth in early 2002.  One of these reproductive units was incomplete, missing one ovary, so total potential cubs could not be determined.  The remaining 11 tracts contained 28 corpora lutea (2.5 per sow):  one single cub, four twins, five triplets, and one potential quadruplet litter.

 

There were 14 (48%) reproductive tracts of sows four years or older that revealed they had given birth in early 2001.  One tract contained only one uterine horn so a complete count of births was not possible.  Of the 13 remaining units, one showed evidence (placental scar) of a single cub, three tracts revealed twins, six showed triplets, and three had quadruplets.  The total of 37 placental scars means an average birth rate of 2.8 per sow.

Written by William K. Igo and Thomas L. Dotson