No one knows better than scientists that the world is full of some foul-smelling shit. So who better to rank the rankest smells than those who have encountered them? On Wednesday, some battered and nauseous researchers took to Twitter to determine which of nature’s smells were the most offensive. The top stinkers comprised a range of animals that were bloated, rotting, and dead. And while the different items varied in gruesomeness, their stenches all shared a common, foul base note.

The twitter thread began when David Steen, a conservation biologist at the University of Auburn tweeted: “RT if you’re a field biologist and you’ve ever asked yourself, ‘Why do I smell bad?’” Horrific stories of inhumane stenches ensued. One scientist described a six-weeks-dead fin whale that had been rotting in the sun. Another recounted his experience with the leaky anal glands of a once-frozen, long-tailed weasel that had thawed in a museum’s taxidermy room. Also making the list were dead frogs and a pile of nice, fresh vulture puke.

Arguably, Steen’s own submission topped the list — a dead sea turtle found in the middle of the road that smelled so bad it made him vomit. The dead turtle’s spot at the top of the stink list was corroborated by Kathryn Wedemeyer-Strombel, Ph.D., a marine biologist from the University of Texas, and wildlife biologist David Syzdek, Ph.D., who said the dead turtle’s stink “destroyed my soul.”

But while smell ranking is an obviously subjective endeavor, there exist compounds that most humans naturally find offensive. Not surprisingly, they are present in many of the items on the scientists’ list.

First up are the sulfur-containing compounds, which are responsible for the dank rotten-egg smells in farts and, it seems, weasel butts. In 2002, some unfortunate souls did a chemical analysis of weasel anal glands and, in the Journal of Chemical Ecology, reported they’d found nine different compounds that contained sulfur. They suspected that the horrific cocktail of sulfur-containing chemicals found in weasel poop is used by other animals as a warning that a weasel passed through the area.

And then there’s the stench of death, which most of the submissions shared. This smell is largely due to four chemicals found in the body: the gruesome and appropriately named cadaverine, putrescine, skatole, and indole. Cadaverine, the smell of which is officially classified as “unpleasant,” is responsible for the foul smell of rotting flesh and is also found in urine and semen. Putrescine, which smells fairly similar to cadaverine, is also what makes bad breath bad. Skatole — which is also found in coal tar — and indole are major components of feces. Strangely enough, skatole and indole are also used in low concentrations to develop flowery scents for perfumes.

Smell is perhaps our most subjective sense -– different odors mean different things and bring about different reactions from people based on their age, lifestyle, and background. But the stench of rotten death is nearly universal, and people move back (or vomit) when they encounter it. This link between potent smell and powerful emotion is likely a result of our evolution –- our early ancestors wouldn’t have lasted very long if they walked up to those dead turtles and decided to have a snack.

Photos via Wikimedia