The Memphis Zoo closed its panda exhibit for 72 hours beginning Thursday to give two giant pandas Ya Ya and Le Le some privacy to try to mate.
A female panda has only three days a year to conceive, said Matt Thompson, the curator of the zoo's mammal wing and overseer of the panda exhibit.
"Once you've missed the window, it's wait until next time," Thompson said.
The two have been placed together during previous mating periods although officials did not hope for much because the male was too young to mate, he said.
For the first time, the zoo will try artificial insemination if the mating is not successful, he said.
But the bears are sending signals that this could be the year for romance, reports AP.
Ya Ya is registering high estrogen levels and is restless, irritable and grumpy all symptoms of fertility, Thompson said.
Meanwhile Le Le has higher than usual levels of testosterone and has been spreading his scent around the exhibit to "mark his territory and let Ya Ya know he's around," Thompson said.
Pandas are an endangered species native to China. Memphis got its pandas almost four years ago on a loan from China, which will own any cub that is produced.