Predator simulation and duration of death feigning in neonate hognose snakes – Burghardt and Greene, 1988
Hognose snakes have a tendency to display a wide range of defensive behaviours that include puffing, hissing, coiling, striking, flattening, and playing dead. Playing dead includes flipping over and sticking their tongue out while releasing a noxious odour to reinforce the idea of death. Their heart rate also decreases significantly and has been compared to tonic immobility seen in opossums. Recovery from the playing death phase is affected by the presence of predators and humans for other animal models like chickens and anoles, thus do hognoses also change recovery times when in the presence of a predator or human? The playing dead phase in hognoses has been considered cataleptic (has visions or trances), narcoleptic (extreme tendency to fall asleep), induced by parasympathetic arousal or adrenal medullary function.
Methods:
This experiment was done on neonate snakes that were newly hatched and not previously fed. Pre-experiment: Snakes were made to play dead by pouring the snake onto an arena that had sand, the experimenter would approach after a min and bend over to loom onto the from approximately 25cm, 10s later the experiment would touch the head of the snake, 10s later would run their hand along the body and 10s later the snake would be picked up and shaken a bit for 5s but not inverted. This usually caused them to play dead. Experiment 1 entailed monitoring the recovery of the snakes when exposed to the presence/absence of a stuffed owl. Experiment 2 entailed the same thing as experiment 1 but now with a human instead and the human had 2 conditions, either looking at the animal or averting gaze. The control was a human hiding behind a counter but in the same room. Observations were done on resuming breathing, retracting tongue, closing mouth, first tongue flick, raising head, turning over, crawling away. 19 snakes were observed but only 6 passed pre-experiment. Each animal was tested either 4 times in experiment 1 and 6 times in experiment 2.
Results:
In both experiments the predator/human stimuli significantly slowed down recovery times. They also looked at bluffing and found no significant differences between treatments. However when looking at the different behaviours shown, the snakes showed more behaviours when in the presence of a predator than when in control.
Notes:
For our own experiment maybe we should incorporate some of these tactics. Maintaining a gaze at the animal or creating some kind of poking device with a mask attached to it might provide similar effects to see bluffing and other behaviours other than playing dead?
Al3xandria 