Introduction

However, a vast amount of interesting data on sleep can be obtained on the basis of behavioral observations.

Technical developments such as light-sensitive cameras and time-lapse recorders, allow unobtrusive recording of animal behavior in enclosures without the need of additional light for observations.

Behavioral observations can serve to determine:

• sleeping sites
• sleep postures
• sleep profiles obtained in animals of different ages living in groups
• seasonal changes in the amount of sleep and the sleep profile
• association of species specific sleep postures with sleep stages