Twenty years ago today, one of the most unusual and fascinating studies of animal sex I have ever come across took place. It was an observational study of the world’s first known case of homosexual necrophilia in the mallard duck. Click here to read a summary of it that I wrote a few years ago. Believe it or not, this write-up is the single most popular blog post I have ever written and it has been read hundreds of thousands of times. Forget human sex--you guys are clearly more interested in reading about dead duck sex than anything.

If you want to learn even more about homosexual necrophilia in the mallard duck, check out the video below in which Kees Moeliker, who authored the original study, discusses how his unusual observation changed his life (necrophilia has a way of doing that, I guess) and what he has learned about animals that mate with other dead animals since publishing it. He has several provocative images to share, as well as some unique explanations for why this behavior occurs.

On a side note, Moeliker commemorates the day of his observation (June 5th) each year with a series of events in the spot that it occurred. He has unofficially dubbed today "Dead Duck Day." Click here for a look at the history of Dead Duck Day and today's events.