Death feigning by grass snakes (Natrix natrix) in response to handling by human "predators."

Area of Science:

• Ethology
• Zoology
• Animal Behavior

Background:

• Death feigning, a form of tonic immobility, is recognized as a crucial antipredator strategy.
• The adaptive significance of death feigning in various species remains incompletely understood, particularly in the context of natural predator interactions.

Purpose of the Study:

• To document and analyze death feigning behavior in the grass snake (Natrix natrix).
• To investigate potential correlates of death feigning, including age, body size, and environmental factors.

Main Methods:

• Wild-caught grass snakes were observed for death feigning responses.
• The study examined variations in feigning behavior based on factors such as presence of hatchlings, body size, and body temperature.
• Behavioral indicators like mouth gaping and muscle tone were recorded.

Main Results:

• Death feigning was observed in 66% of wild-caught grass snakes, but absent in laboratory-hatched individuals.
• Behavioral manifestations ranged from mouth gaping to loss of muscle tone and voluntary supination.
• No significant correlation was found between death feigning and body size, body temperature, or initial movement status, except for hatchlings.

Conclusions:

• Death feigning is a notable behavior in grass snakes, with its occurrence varying by developmental stage.
• Environmental factors like temperature and body size do not appear to significantly influence the expression of death feigning in adult grass snakes.
• Further field research is needed to ascertain the ecological role and adaptive value of death feigning in grass snakes when facing natural predators.