Some pups are able to suckle successfully from two females. Sometimes a cow will share her pup with another cow, or a weaned pup is adopted by a foster mother after the real mom has departed. Usually the foster mother has lost her own pup. These shared pups are called "superweaners" or "double mother suckers," and they typically grow much fatter than other pups. We had three superweaners in our Mirounga Beach colony this year, all males.
Colleen shared her pup with another cow. The other cow's pup washed out to sea during one of the big winter storms. Below is a picture of Colleen's weaner hauling himself out of Mirounga Beach.
Grasshopper's pup was adopted by a another cow after Grasshopper departed. The foster mother nursed him for an additional 12 days. He is the biggest weaner on the Farallones. In the second picture, he is stuck in a pile of driftwood that washed into Mirounga Beach after one of the big storms. He eventually worked his way out after being stuck there for two days.