February 3, 2009

Older Killer Whale Moms Do A Better Job Raising Young

Researchers reported on Monday, that older mothers may do a better job raising their children than younger, less-experienced moms, amongst killer whales.

The researchers looked over 30 years of data to find that calves born to the oldest killer whales were 10 percent more likely to survive the critical first year of life than calves born to younger mothers.

"Older mothers appear to be better mothers, producing calves with higher survival rates," Eric Ward of the Northwest Fisheries Science Center in Seattle and colleagues wrote in the journal Frontiers in Zoology.

The killer whale female becomes mature around 15 years of age, and stops producing at around 40.

"Our work supports previous research showing that menopause and long post-reproductive lifespans are not a human phenomenon," the researchers said.

Researchers thought for years that humans were the only creatures that evolved menopause, and one theory was that having a healthy and unencumbered grandmother around to help take care of the babies benefited babies and mothers alike.

However, killer whales also have menopause.  The whales live long lives, with males living up to 50 years and females as much as 90 years old.

"Older females may be more successful in raising young because of maternal experience, or they may allocate more effort to their offspring relative to younger females," the researchers wrote in their study.


On The Net:

Northwest Fisheries Science Center

journal Frontiers in Zoology