The National Zoo’s female giant panda may be pregnant, the Washington Post reports. Volunteers are monitoring Mei Xiang around the clock after zookeepers noticed behavioral changes that indicate the mom to celebu-panda Tai Shan is expecting, including creating a bamboo den in a dark and quiet place, and cradling food and other objects. Mei Xiang was artificially inseminated in January; if she is pregnant, the cub should come within 3 weeks. (More pregnancy stories.)