The Debunker: Did an Positive Pregnancy Test Mean the "Rabbit Died"?


If spring is, as the poets tell us, a season of rebirth, then it stands to reason that autumn is a season of death. November is when Christians observe All Souls' Day, the "Day of the Dead," celebrating the souls of the faithful departed. It's also the month that brings with it the most dead leaves, and probably the most dead turkeys as well. But a lot of what you think you know about death in the natural world is "gravely" mistaken. Ken Jennings, of Jeopardy! fame, is with us all month to debunk a lot of myths about our furry friends who encounter the undiscovered country…or at least a "farm upstate."

The Debunker: Did an Positive Pregnancy Test Mean the "Rabbit Died"?

Maybe this term is dropping out of sight in the rear-view mirror of time nowadays, but for decades, pregnancy tests were colloquially called “rabbit tests.” “The rabbit died” was a winking, jovial way to announce you were expecting a baby, which is pretty weird if you think about it. “We have a joyous event on the way, the beginning of new life! Allow me to metaphorically compare it to the death of a cute, innocent animal of a type normally associated with vitality and fertility!”

The Debunker

It's true that the "rabbit test," alongside close variants that used mice and frogs instead, was the earliest reliable pregnancy test rolled out by medical science. In fact, tests like these were the best clinical way to medically confirm pregnancy until more direct lab tests were rolled out in the 1960s. The rabbit test was born in 1931 at the University of Pennsylvania, when researchers discovered that the urine of a pregnant woman, if injected into a rabbit, would increase the size of the rabbit's ovaries. This is because the blood and urine of pregnant women contains the reproductive hormone hCG. Home pregnancy tests, which hit U.S. store shelves in 1977, still operate on the principle of detecting hCG, but it's much easier to pee on a little stick than it is to pee on a rabbit's ovaries.

The expression "the rabbit died" reflects a common misconception about the old bunny-based pregnancy tests: that a rabbit would die if the sample injected came from a woman who was pregnant, but the rabbit would survive if the woman was not. In fact, that's not true. Nothing about the injection or the hormones was fatal to the rabbit either way. What was fatal was getting dissected so scientists could get a closer look at their ovaries! In other words, back in the early days of the rabbit test, the rabbit always died, on a surgical table. It wasn't until decades later that doctors learned how to examine rabbit ovaries without killing the rabbit. From that point on—yay!—all rabbits survived the rabbit test. Even if (congrats!) the "rabbit died."

Quick Quiz: The fearsome rabbit named General Woundwort dies at the end of what classic 1972 novel by Richard Adams?

Ken Jennings is the author of twelve books, most recently Planet Funny and co-hosts the most important podcast in human history, Omnibus. He's also the proud owner of an underwhelming Bag o' Crap. Follow him at or on Twitter as @KenJennings.

Watership Down

Yes, Watership Down. And the cartoon version was actually incredibly true to the novel. Highly recommended reading.

The Killer Rabbit of Caerbannog

I can’t read past “did an positive.”