To avoid becoming a meal, some animals simply fake it until they make it. And fake deaths with several unappealing elements may make the whole display more efficient, a study finds.
Dice snakes that bleed from the mouth and cover themselves in musk and feces spend less time pretending to be dead than those that don’t, researchers report May 8 in Biology Letters. These defenses, the scientists suggest, could be working in synergy: heightening the overall impact of the display while helping the snake escape a predator more quickly.
Death-feigning is a common defensive tactic across the animal kingdom (SN: 11/1/23). It often involves prey lying still while exposing vulnerable body parts, making it a high-risk but potentially high-reward maneuver. Many predators won’t touch apparently dead things, perhaps because of parasites, or maybe because the lack of movement doesn’t elicit their predatory response.
The dice snake (Natrix tessellata) is particularly elaborate when staging its demise. When captured, it will thrash around and hiss before covering itself — and probably the predator — in feces and musk. For the grand finale, it opens its mouth agape, sticks out its tongue and fills its mouth with blood.
Biologists Vukašin Bjelica and Ana Golubović of the University of Belgrade in Serbia wanted to know if these combined defensive efforts make the whole ploy happen faster. They captured 263 wild dice snakes on the island of Golem Grad in North Macedonia and recorded any smearing of feces or musk. The team then placed the snakes on the ground and stepped out of sight, mimicking the actions of a hesitant predator, before recording all subsequent behaviors.
Just under half of the snakes smeared themselves in musk and feces, while around 10 percent bled from the mouth. Some fake deaths without musk, poop or blood lasted almost 40 seconds. The 11 snakes that combined all three defenses spent, on average, around two seconds less feigning death.
Perhaps the trifecta of tricks heightens the intensity of the show for the predator, cutting the animals’ interaction short and increasing the snake’s chance of survival. “Two seconds might not be a lot but can be just enough for a snake to mount an escape if the predator backs away from attacking it,” says Bjelica. “Even the smallest chance can make a difference in being eaten or not.”
Over the last decade, says evolutionary ecologist Tom Sherratt of Carleton University in Ottawa, “there has been a push not to see antipredator responses in isolation, but as an integrated whole.” The new findings, he says, raise some questions: “Why the variation? Why don’t they all have auto hemorrhaging and fecal display? It could be something about their experience, but there’s variation there to explain.”
Ecologist Katja Rönkä of the University of Helsinki says the next step is to study the predator side of this behavior: “Why are they deterred by ‘dead’ animals, especially since they just saw them alive?”
