Older mothers may do a better job raising their children than younger, less-experienced moms, at least among killer whales, researchers reported on Monday.

They studied 30 years of data to show 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.