Back in the day,  a common expression used to tell someone that one was pregnant was that “the rabbit died.” This euphemism came from the “Friedman test,” a pregnancy test developed in 1931 by a pair of doctors at the University of Pennsylvania in which urine from a woman was injected into the ovaries of a rabbit. If the woman was pregnant, the rabbit’s ovaries would change because of the presence of human chorionic gonadotropin. It is a fallacy that the rabbit died only if the woman was pregnant. Since the rabbit had to be surgically opened in order to examine its ovaries, all tested rabbits died. Happily, advances no longer rely on rabbits, but starting in 2013, zoos did come to rely on a Beagle to determine pregnancy.

Specifically, the zoos relied on a Beagle named “Elvis” to determine if their polar bears were pregnant, and Elvis got it right 97 percent of the time. To everyone’s relief, Elvis never had to meet a Polar Bear, nor did he come remotely close to death. He did, however, have to get up close and personal with fecal samples sent to him from zoos around the country. Since Polar Bears only give birth only about five times in their lives, and then to only one or two cubs in a litter, a Polar Bear pregnancy is special – but hard to determine. Lady Polar Bears often become “pseudopregnant” showing all the signs of pregnancy after mating, like weight gain and even nesting behavior, but eight months later, no cub. Lab tests are often inaccurate because the hormones in pseudopregnant and pregnant bears are close enough to throw off lab-based pregnancy tests.

Elvis, now six years old, was trained to sniff for five proteins consistent with pregnancy starting with 200 samples from bears that had already given birth. Trainers threw every kind of curveball at Elvis, but he consistently found the target odor. In the most surprising case, Elvis identified a pregnancy in a sample that zoologists had labeled as negative. It was thought Elvis was tripping up, but sure enough, a few months after the sample was collected, the Polar Bear gave birth to a cub. There was no getting it past Elvis. Read more about Elvis here in a story from 2013.

Image of Elvis, the Beagle