Three California sea lions born at ARTIS

Both pups began nursing from the same mother. The pregnant mothers were lying side by side when the first pup was born. The mother of the first pup is inexperienced and paid little attention to her pup. The experienced mother, who is the grandmother of the first young sea lion, instinctively stepped in as soon as the pup began searching for milk. She gave birth to her own pup 24 hours later, and is now nursing both. The nursing mother is currently being given a large amount of fatty fish. Both pups are male. They will mostly remain in indoors for the time being, where they are not visible to visitors, and can decide for themselves when they want to go outside.

A third California sea lion was born on the first day of summer. The pup has already begun nursing. We do not yet know whether the pup is a male or a female. The mother started having contractions on Monday and the pup was born outside near the basin on the night of 21 June. The mother and her pup then retreated to the indoor enclosure, where they are strengthening their bond away from the group.

The California sea lion (Zalophus californianus) is found in the wild along the west coast of North America. During the mating season, they form harem groups led by one male, the dominant ‘beach master’. California sea lions always give birth during the same time of year, from May to June. They have a gestation period of 11-12 months. The birth usually takes just a few minutes. Sea lions generally give birth to one pup per litter, but multiple births can occur as well. One mother is therefore able to nurse several pups at a time. Sea lions have four retractable nipples and produce milk with a very high fat percentage.

After approximately 10 months, the pups will wean off their mother's milk and start to eat fish; after a year, they will be independent. Newborn sea lions are not yet able to swim. It takes around ten days before they learn to swim with the help of the other sea lions. It has been six years since the last sea lion pups were born at ARTIS. With the arrival of these new pups, ARTIS now has seven sea lions: one beach master and a harem of four females and two pups.

When sea lion mothers go searching for food, they leave their pups behind with other pups, who together form a crèche. During this time, they learn from one other and from the slightly older pups. The mothers return to give their pups milk. Mothers and pups recognise each other by their specific vocalisations and scent. The ‘imprinting’ of this sound and scent begins as soon as the pup is born. The first pup born at ARTIS is establishing this bond with the nursing mother instead of with his own mother, as she gave him little attention.