Fig 2. Elephant inactigrams.

Inactigrams for each elephant during the entire recording period, from April 14 to May 18. Each solid mark indicates a period of 5 minutes or more when the trunk of each elephant was completely immobile, the elephant presumably being asleep. The grey regions represent the period between sunset and sunrise. Note that the vast majority of sleep occurred during the hours leading up to sunrise, but occasional sleep episodes could occur at different times throughout the 24-h period.