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The black bear is not a threatened or endangered species. However,
it is vulnerable to extreme population fluctuations because of its
mating habits and reproductive cycle. In New Mexico, breeding doesn’t
begin until a sow is almost six years of age, and mating occurs only
once every two years. Consequently, BearWatch is concerned that
wildlife management policies must take care to protect the population
of our black bears.
In New Mexico, black bears breed between mid-May
and July. Gestation takes seven to eight months. Delayed implantation
of the eggs enables the female to breed in the summer and give birth in
the winter. This delayed implantation has been termed “an effective
means of birth control”. If it has been a good feeding season and the
sow has plenty of fat reserves going into the winter season, then all
the fertilized ovum will implant, meaning a large litter (up to 3); if
it has been an average feeding season, maybe just one or two ovum will
implant, resulting in 1-2 cubs. And if it has been a sparse feeding
season, the ovum will not implant at all, so that the female bear can
use all her fat reserves to keep herself alive. Therefore, even though
a bear mates in June, it could be as late as November before the
fertilized eggs are implanted. Cubs will stay with their mother 1-2
years. Therefore the female mates about every 2 years, shortly after
“evicting” the cubs. |
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