The turtles are one of the world's most endangered species of freshwater turtles, The New York Times reported Wednesday. The only female known to exist is an 80-year-old turtle who has lived in a zoo in southern China for half a century. Last May, scientists loaded her up in a van and drove her 600 miles to a zoo in the city of Suzhou, where a 100-year-old male turtle awaited, the newspaper said.

While the mating resulted in the production of about 100 eggs, only about half were fertilized and those embryos died in development. The Turtle Survival Alliance said many of eggs had very thin or cracked eggshells, which suggests the turtles were not being being fed properly.

Xie Yan, the China program director for Wildlife Conservation Society, said the diet of the female turtle has been changed and scientists will try to mate the two turtles again next year.