Aspiring actors in need of inspiration for their next dramatic death scene needn’t look any further than dice snakes (Natrix tessellate). The serpents fake their own deaths to avoid predators.
In a bizarre new finding, researchers have discovered dice snakes include dramatic practical effects in their charade such as smearing themselves with faeces and oozing blood from their mouths. Snakes which do this are more effective actors and spend less time feigning death overall.
“When captured, they will vigorously struggle and hiss while expelling and coating themselves in musk and faeces,” the authors describe in the new study published in the journal Biology Letters.
“Eventually, they will become immobile, with a gaping mouth and protruding tongue in a death feigning display, which can sometimes be accompanied with autohaemorrhaging from the mouth.”
Death feigning is a high risk, high reward antipredator defence seen in a wide variety of prey animals. The behaviour often involves lying motionless with their vulnerable parts exposed to the predator, which exploits predators’ learned aversion towards sick or dead prey.
The researchers, from the University of Belgrade in Serbia, were interested in whether adding a repertoire of gruesome acts intensifies the display to make it more dissuading to predators.
On Golem Grad island in North Macedonia they observed wild dice snakes’ behaviour in response to humans acting as proxy predators.
They caught 263 snakes: “…directly in the field by lunging at them in the open, or we found them underneath natural cover,” they write.
“At capture, each snake was grabbed approximately at mid-body with one hand, since it has been previously shown that holding snakes at different parts of their body induces different behaviours.
“During the first 30 seconds after capture, while holding the snake in the air, we noted the occurrence of smearing when the snake coated itself in musk and faecal discharge, which is hypothesised to repel the predator.”
The snake was then gently handled to imitate the actions of a generalist predator and placed supine on its back. The handler then stepped out of view of the snake, a move to mimic a predator’s hesitation to eat it.
They then timed the duration of death feigning behaviour (laying immobile with a gaping mouth and protruding tongue).
Out of 263 snakes, 124 made the death feigning display more convincing by smearing musk or faeces, and 28 secreted blood from the mouth. The snakes that combined all of the tactics spent approximately 2 seconds less in the death feign.
“Sending the right signals to a predator – an immobile individual with a foul smell and visible blood –allows for a more intense display,” the authors write.
“This reduces the time spent lying exposed to the predator while at the same time dissuading further attacks.”
