A lack of information about how many endangered cats live in the wild is hampering efforts, the conservation group WWF said.
With only some 50 left in the wild, the animal faces extinction without captive-breeding programs in zoos.
Shera, a 9-year-old lion, gave birth to four cubs over the weekend at the National Zoo.
The leopard was seen leaping off a building site as people scrambled out of the way.
Many unlikely bonds have formed between animals that normally have nothing to do with each other.
Photographer Steve Winter has traveled to India, Sumatra, Myanmar and Thailand to photograph one of the most endangered big cats in the world.