The North Carolina Zoo has announced the birth of three litters of American red wolves, which are critically endangered and number less than two dozen in the wild. The zoo said Monday that 12 pups were born during over three days at the end of April. According to zoo officials, all the pups and their mothers are healthy and doing well. The newest pups bring the total number of red wolves currently in the North Carolina Zoo’s breeding program to 36. Officials say that makes the pack at the North Carolina Zoo the second-largest in the U.S. after another zoo in Washington state.