We found 14 dead fawns, four were killed by black bears, four were abandoned by the mothers, three died in accidents (including two drownings), two were stillborn, and one died of unknown causes.
Fawn losses averaged 32 percent for three years when bears were present in the enclosure, compared to 10 percent mortality when these predators were absent. In other words, bears apparently killed about 22 percent of the fawns.
Interestingly, prime-age does lost only slightly more fawns when bears were present versus absent ( 17 percent and 11 percent, respectively). However 2- and 3-year-old mothers suffered heavier fawn mortality when bears were present ( 32 percent and 58 percent, respectively), versus absent ( 13 present and 4 percent, respectively).
These findings also hint that outright defense of fawns by multiple does — including the experienced matriarch — lessens predation and lowers newborn mortality rates for first-time mothers. By comparison, the dispersing 3-year- old doe has less chance of such matriarchal support in fending off predators and runs the risk of greater fawn loss.
In whitetails, maternal success largely determines the young doe’s social standing in the herd. Those who fail to rear their first fawns revert to subordinate yearling behavior by seeking their mother’s leadership.
Since such domination has potential physiological and reproductive consequences, I examined the performance of 73 young does in detail during their
LEONARD LEE RUE III PHOTOS
A white-tailed doe’s maternal success forever determines the young doe’s social standing in the herd. Those who fail to rear young revert to subordinate positions in the herd’s pecking order.
first and second breeding seasons; 55 successfully reared their first litter whereas 18 failed.
Although there was no differences in physical condition or breeding history among does at yearling age, certain aspects of their performance differed when they were 2½ years old. For example, although the two groups were equally productivity, the maternally unsuccessful does bred later as
Ozoga, J. J., L. J. Verme and C.S. Bienz. 1982 “Parturition Behavior and Territoriality in White-tailed Deer: Impact on Mental Mortality.” Journal of Wildlife Management 46: 1-11.
Ozoga, J. J., and L. J. Verme. 1982. “ Physical and Reproductive Characteristics of a Supplementally-Fed White-tailed Deer Herd.” Journal of Wildlife Management, 46:281-301.
Ozoga, J. J., and L. J. Verme. 1986. “Relation of Maternal Age to Fawn-Rearing Success in White-tailed Deer.” Journal of Wildlife Management, 50:480-486
Ozoga, J. J., L. and J. Verme. 1986. “Initial and Subsequent Maternal Success of White-tailed Deer.” Journal of Wildlife Management, 50:122-124.
compared to the successful mothers during their second breeding season (Nov. 25 versus Nov. 17, respectively).
Does that failed to raise their first litter also bore more male progeny the second season, as compared to the successful mothers ( 64. 7 percent males versus 38. 9 percent males, respectively).
These differences undoubtedly have adaptive significance. Because a successful 2-year-old doe tends to disperse to new range to raise her second litter, it is important for her to give birth early in the season to claim a favorable fawning territory. Giving birth to female progeny also enables her to form her own family group.
In contrast, the unsuccessful 2-year-old doe often remains on ancestral range for another year. The delayed birth of her second litter and tendency to conceive males (which ultimately disperse) would minimize future competition with the matriarch for territorial fawning space.
Nutrition clearly sets the doe’s reproductive schedule. However, social factors and learning behavior can be just as important in governing newborn fawn survival prospects.
Our findings indicate the newborn fawn’s bed site habitat, movement patterns, social and/or spatial relationships, and evasive tactics when threatened by predators are largely maternally controlled. Because a doe’s fawn-rearing skills improve with experience, older mothers are more successful than younger ones, especially when social crowding or predation seriously threatens newborn fawn survival.
Regardless of prevailing environmental constraints, maximum fawn-rearing success will occur when physically mature, maternally experienced does comprise the bulk of the breeding herd.
— John J. Ozoga is a retired research biologist from Michigan. This year marks his 15th anniversary as Deer & Deer Hunting’s research editor.
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