For the first time, biologists have documented zoo-reared northern leopard frogs surviving a winter in the wild at the Columbia National Wildlife Refuge in Eastern Washington — despite the presence of invasive American bullfrogs that nearly wiped them out. Thanks to targeted bullfrog control, some of the northern leopard frogs released last August by the Oregon Zoo and Northwest Trek Wildlife Park are surviving, an important turning point in the recovery of this endangered species. “This is great news,” said Jen Osburn Eliot, who oversees the Oregon Zoo’s frog-rearing efforts. “We care for these frogs at the zoo until they’re …