Zookeepers were eager to see captive platypuses mate because, only one platypus couple, Jack and Jill, had bred in captivity, and that was in their native Australia. In the spring of 1951, when zookeepers put Cecil in Penelope's enclosure, she began behaving with erratic aggression: "scratching furiously with all of her 20 sharp claws," running into the water, and rolling over. The next year, during the North American spring, Penelope was more receptive to Cecil's presence. This time, when they were near each other, Penelope did not behave unusually.
