Now, Pittsburgh zookeepers want to know if the Amur tigers' loving session was productive.
Tiger pregnancy is determined by testing hormone levels in stool samples, which takes several weeks.
But there are always the unofficial signs.
The zoo's lead carnivore keeper, Kathy Suthard, says Toma is cranky and hungrier than usual, just as she was during her first pregnancy.
The zoo is encouraged because Toma already has 18-month-old cubs. Her mate, Globus, sired four cubs at the Riverbanks Zoo in Columbia, S.C.
Amur tigers, formerly known as Siberian, are endangered. There are about 190 Amur tigers in U.S. zoos and less than 400 in the wild.
