How do you transport a 234-pound baby to New York City? If he’s a 15-week-old walrus rescued from the open ocean off Alaska, the answer is a jumbo-size crate aboard a FedEx cargo jet, accompanied by a veterinarian and a handler.

“If he’s calm and comfortable, no worries,” said Jon Forrest Dohlin, director of the New York Aquarium, which will receive the walrus calf, named Mitik, on Thursday. “But his needs and comfort come first. So he may very well travel with his head in our keeper’s lap.”

Mitik will arrive at an important moment for the Brooklyn aquarium. Situated just off the Coney Island Boardwalk, the aquarium, part of the Wildlife Conservation Society, is one of only several institutions in the United States that exhibit walruses. One of its two walruses, Nuka, is 30, an old-timer by walrus standards.

Because walruses are such social animals, the aquarium would be hard-pressed to keep the other walrus, the 17-year-old Kulu, were Nuka to die. “Our concern is that our very elderly walrus could pass away, as these things go,” Mr. Dohlin said, “and that would leave us in a pickle because we really wouldn’t want to have a solitary animal.”