Two rare lemurs, among the only four captive-born monkey-like mammals in the world, are progressing on a diet of pine needles and other North Carolina delicacies that may be the key to their survival, researchers said Thursday.

Aurelia, a female born in December, and Tiberius, a 41/2-month-old male, "are doing really well," said Dr. Elwyn Simons, head of the Duke Primate Center where the lemurs, known as propithecus, or sifaka, were born.The two small, woolly, cat-size primates are graduating to adult food and weigh about a third of grown-up lemurs' 9 to 10 pounds.

The black and white, big-eyed, leaf-eating mammals are native only to the island of Madagascar. But deforestation for cattle and coal on the island has endangered the rare species.

Duke is the only research center to breed the sifaka successfully in captivity, the first delivery in 1972 and a second in 1986. Simons said the rare lemurs born in other laboratories never have lived past infancy.