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Mother-cub bonding

February 10, 2010 - 5:58 PM CST

We have a lot to learn about mother-cub bonding.  We’ve never been able to watch a mother and cub like this before.

When the cub was born, we didn’t know what to expect.  Lily surprised us with immediate sweet grunts that mothers use only when they are concerned about a cub.  She made those sounds even before the cub cried.  We believe Lily immediately bonded with the cub at birth.  It's hard to imagine a better mother than a bear in a den.  She's totally invested, dedicated, protective, predictable, and comforting.  She has nothing else to do but snuggle and nurse the cub 24/7.  She responds to each cry.  Are there different cries for hungry, wet, cold, tired, potty time, over-stimulated, or need for closeness?  We don’t know.  Does the cub have emotional needs at this point, or are the needs purely physical?  Hard to tell.

Does mother and cub become imprinted on the smell of the other?  For animals with such legendary senses of smell like bears, one would think so.  But we wonder.  Mothers in dens will suckle and care for any cub.  Mothers have such strong mothering instincts that they will adopt strange cubs that are left at entrances of dens.  They're not like herd animals that are particular to give their milk only to their own young which they recognize by smell.   Hibernating bears evidently have never been subject to natural selection for that trait.  A mix-up in cubs would be impossible while they are still in dens.  A few days or weeks after leaving the den, mother bears become more selective.

Cubs may be especially prone to bonding between the time their eyes open at 6 weeks and the time they leave the den at 12 weeks.  Like puppies, captive cubs that are removed from their mothers during that period readily bond with humans that bottle-feed them.  If a cub is raised by people during that period and then given to a wild mother for adoption, it can be difficult to get the cub to accept the new mother.  Biologists who tranquilize mother bears in dens see changes in cub acceptance when the cubs approach 5 pounds and are about to emerge at 10-12 weeks of age.  When biologists pick up younger cubs and tuck them into their jackets against their chests for warmth, the cubs are content.  Some even make the motor-like hum.  But if the biologists go to dens when the cubs are nearly ready to emerge, the cubs are no longer trusting.  They greet the biologists with screams, bites, swats, and claws.

We wish we knew what is going on in the heads of Lily and the cub.  What emotions do they feel?  We wish we knew the meanings of the different cries.  When the cub becomes more visible, it might be easier to tell.

—Lynn Rogers and Sue Mansfield, Biologists, North American Bear Center

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