LONG ISLAND AQUARIUM PHOTO | Jelly, a North American river otter, gave birth to four pups this weekend.

The Long Island Aquarium in Riverhead closes during most overnight hours — but nature doesn’t stop.

That was apparent Saturday morning, when staffers discovered four newborn North American river otters in the Otter Falls exhibit, which opened in 2008.

The pups were born to the aquarium’s river otter couple, Peanut Butter, the male, and Jelly, the female. Officials say the pups are healthy, and are being kept in a secluded area — away from the public’s eye — with their mother as they nurse, sleep and grow.

“While it’s still very early, they all seem to be doing well and Jelly is being a fabulous mother as expected,” aquarium officials said in a release. “The otter pups and mom are inside in the holding areas of the exhibit while the male, PB, is still on exhibit.”

The pups won’t be visible to the public until they start moving on their own, which will take about a month. They’ll nurse for four months.

In the meantime, the aquarium released photos of the newborns.

LONG ISLAND AQUARIUM PHOTO | The four river otter pups born this weekend.

From the aquarium:

The playful North American river otter (Lontra canadensis) is equally at home in the water as it is on land. Once abundant in U. S. and Canadian rivers, lakes, and coastal areas, the North American river otter can today be found in parts of Canada, the Northwest, upper Great Lakes area, New England, and Atlantic and Gulf Coast states. 

Members of the weasel family, river otters enjoy sliding down muddy and snowy hills, bouncing objects on their paws, playing tag, and wrestling.