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It's very difficult to learn if polar bears are pregnant. They don't really "show."
Ultrasounds are often ineffective. And, of course, zookeepers are reluctant to get too close to a giant carnivore.
To learn whether its polar bear, Cranbeary, is pregnant, the Denver Zoo has turned to a beagle named Elvis. He is trained to sniff a bear's poop and, for reasons that are still a mystery to scientists, detect if a bear is pregnant.
Colorado Matters host Ryan Warner speaks with Erin Curry of the Cincinnati Zoo, who's involved in the research.