Nipple Order

Lily ate more snow to make more milk.  Hope was good and bad.  Sometimes she sat nicely beside Lily without too much protest as the cubs nursed.  We were impressed by that because in summer we had seen her savagely and repeatedly drive her mother off food.  Lily meekly stayed out of the way while hungry Hope ate.  So we wondered what made Hope so good with the cubs in the den.  But nobody’s perfect.  Last night Hope pulled a cub off Lily’s nipple.

That made us think about ‘nipple order.’  Mother bears have 3 pair of nipples for a total of 6. By the time families leave the den in the spring, each cub generally has claimed a pair of nipples as their own. We used to think nipple order was always sorted out in the den, but close observation of June’s last litter showed us that is not always the case. Jewel and Jordan fought over nipples for a week after the family left the den in 2009.

Once the order is established, each time a family settles in to nurse the cubs sort themselves out and land on their own pair of nipples. They work both nipples in the pair—switching often between the two. There may be a bit of snitching before all the cubs settle in and some switching around at the end of the nursing bout as they check for any drops a sibling missed, but each cub primarily nurses on the same pair of nipples each time. This is referred to this as ‘nipple order.’

Last summer, when Hope had all 6 nipples to choose from, she chose one from each of two pair—the uppermost one on the right side of Lily’s chest and the corresponding one on the left side. Likely these were the two that produced the most milk once Lily resumed lactation after they reunited.  These two nipples were further apart than a pair of nipples would be and it was odd to see little Hope moving back and forth from one side of Lily’s chest to the other as she nursed.

We are wondering how this mixed-age litter of Lily’s will sort itself out. Will Hope be able to reclaim her two nipples? Will one of the new cubs assert dominance over Hope? Will Hope defer to the cubs? Some of the cub cries we are hearing may be competition between them for nipples.

A Lily fan who is a top scientist in London inquired about the snarling brown bear in the Natural History Museum there.  He was told by a museum official that they would look into it.

The same Lily fan wondered if it were possible to set up a British ‘Friends of Bears’ to help the North American Bear Center spread its message and collect donations that would be tax deductable there if the Friends of Bears was registered as a nonprofit in the UK.  Might there be a Lily fan in the UK who could explore that?

Today, you registered over 10,000 votes to elevate Ely from 73^rd place to 59^th place in the Reader’s Digest race to win money for Ely and its school.  Thank you.  This again shows the value of the radio-collared bears and their fans to the town.  To vote, go to http://wehearyouamerica.readersdigest.com/town.jsp?town=ELY&state=MN

Thank you for all you are doing.

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