Physiological responses associated with feigned death in the American opossum

Area of Science:

• Physiology
• Animal Behavior
• Zoology

Background:

• The American opossum (Didelphis marsupialis) is known for its unique 'playing possum' defense mechanism.
• Understanding the physiological correlates of this behavior is crucial for comprehending stress responses in mammals.

Purpose of the Study:

• To investigate the physiological changes in American opossums during mild provocation and death feigning.
• To quantify alterations in heart rate, respiratory rate, and body temperature.

Main Methods:

• Monitoring heart rate, respiratory rate, and body temperature in four free-ranging American opossums.
• Inducing mild provocation (approach of man or dog) and death feigning (vigorous tactile stimulation).
• Administering atropine to assess its effect on physiological responses.

Main Results:

• Mild provocation led to a 12% decrease in heart rate and a 31% reduction in respiratory rate.
• Death feigning resulted in a 46% decrease in heart rate, a 30% reduction in respiratory rate, and a drop in body temperature.
• Opossums remained conscious during death feigning, evidenced by heart rate changes upon re-approach.
• Atropine did not alter behavior but abolished bradycardia.

Conclusions:

• The 'playing possum' behavior in American opossums is associated with significant physiological suppression.
• These findings provide insights into the autonomic nervous system's role in extreme stress responses in this species.