These snakes play dead, bleed and poop to avoid being eaten

When dice snakes face a predator, the most theatrical representatives of the fish-eating species sometimes go to extremes to avoid becoming dinner.

On Golem Grad, a lake island in North Macedonia, dice snakes threatened by birds play dead by becoming stiff or limp, smearing themselves with feces and musk and even bleeding from their mouths. Death causes muscle relaxation and may cause animals to defecate or urinate after death.

Researchers at the University of Belgrade in Serbia simulated predators by lunging at the snakes, grabbing them and pinching them around their midsections. The researchers tested 263 snakes in the field and found that 10.6 percent of them released “small puddles” or even “dripping mouthfuls” of blood from their mouths. The study notes that increased levels of stress hormones can trigger the phenomenon by increasing the snakes’ blood pressure.

The snakes that feigned death did so “for a shorter time than those that did not,” Belgrade Institute of Zoology research associates Vukašin Bjelica and Ana Golubović wrote in their new study on Wednesday. The study, published in the journal Biology Letters, found that snakes that smeared themselves before bleeding spent about two seconds less playing dead.

The study notes that other factors such as the snakes’ gender, their size and previous experience with predators may have influenced how long they played dead for.

“Two seconds may not be a lot when you read the newspaper, but it could be enough for a snake to successfully escape,” Bjelica said New York Times. “They really commit to the role, depending on the person,” Bjelica added.

The researchers said they saw adult dice snakes feign death more often than young snakes (35.3% vs. 31.9%, respectively); However, the young snakes they studied never played dead. The authors wrote in the study that young snakes “are at greater risk of becoming victims of predators and therefore should avoid risky anti-predator displays.” “

Many species defend themselves through thanatosis or by playing dead. Other examples of creatures that feign death include hognose snakes, Virginia possums, and brown widow spiders. People sometimes use such tactics; The US National Park Service recommends that people first try to play dead if attacked by a brown bear.

“The origin and evolution of (feigning death) is quite puzzling when you think about it,” Bjelica said in an email to PopSci. “When you’re attacked by a predator, it’s kind of counterintuitive to make the predator’s job easier by playing dead,” he added. But when it works, playing dead can draw predators’ attention to other prey. An unpleasant smell or taste can also cause predators to go elsewhere. According to Bjelica, playing dead “requires very specific circumstances to be effective.”

The researcher said he has been studying Golem Grad’s snake population since 2018. While the island is not home to mammals, the snakes there face “heavy avian predation,” Bjelica said, from birds such as herons, seagulls, corvids and some birds of prey.

Regarding the simulated predators that made the study possible, it was found that none of the snakes tested “were injured during processing and no snake showed signs of distress upon release,” the authors wrote at the conclusion of the study.