At what age do black bear cubs have a good chance of surviving on their own?

Question

A woman in a semi-rural Maryland neighborhood was injured by a black bear sow a day or two ago. See The Washington Post. She heard a dog barking, went out with her dog on a leash to investigate and was attacked in her driveway. She had her cell phone with her, and called for help. She needed many stiches and, according to WUSA*9, may have a fractured hip and will remain in hospital for several days.

According to the WP (link above):

Authorities said they think the woman inadvertently came between the sow and her three cubs.

The bear, collared, and well known in the neighborhood because of a characteristic limp, was tracked and killed.

Wildlife specialists had found one of the sow’s three cubs the night of the attack, subdued it with a dart gun and held it until daybreak before it was released. The other two cubs, all likely about 10 months old, also were spotted and determined to be in good health — and able to live on their own.

The question: At what age do black bear cubs have a good chance of surviving on their own?

I hope the answers will consider variables that affect the answer including, but not necessarily limited to: (1) climate and (2) the effect of denning on their own the first winter after being weaned. As for (1), I would expect these Maryland cubs to have a better chance than cubs of the same age in a climate with a colder, longer winter. I'd also expect -- but do not know -- that there would be a great advantage to denning with their mother rather than on their own.

Answer 1

There is probably no perfect answer to your question as different studies will indicate some amount of variation. However it seems that black bear cubs which are usually born in January and generally stay with their mothers for about 17 months are self-sufficient at the age of 5 or 6 months. Under some circumstances mothers with cubs will accept strange cubs in their dens. Cubs will instinctively make dens in the fall.

The following is taken from the USDA in Minnesota: AIDING THE WILD SURVIVAL OF ORPHANED BEAR CUBS.

Reliable methods for aiding the wild survival of abandoned or orphaned bear cubs are needed for use with threatened and endangered species and for use with black bears (Ursus americanus) in areas where populations are low. Methods used in northeastern Minnesota and other areas are reported or reviewed. Options include: (1) returning abandoned cubs to their mothers, (2) introducing orphaned cubs to wild foster mothers, (3) leaving orphans alone that have reached the age of self-sufficiency or transporting them to more favorable areas, and (4) raising orphans for release at the age of self-sufficiency. Mothers with cubs will readily accept strange cubs in their dens and, under some conditions, at other times of the year. Foster mothers may need to have supplemental food placed in their territories if they are to raise adopted cubs, especially if adoptions enlarge litters to more than 3 cubs. Although black bear cubs normally remain with their mothers for 17 months, they are commonly self-sufficient at 5 months of age (by July), and they instinctively construct dens in fall. Cubs raised in captivity and released at 5 months to 6 years of age have reportedly shown good survival with few instances of nuisance problems. Most of these releases were in remote areas of Idaho and Michigan.