Abstract
Since the analysis of animal behavior is a central element of ethology
and ecology, it is not surprising that a great deal of research has been
conducted describing the behavior of various ungulates. Most studies
were conducted during the daylight hours, thus much less is known about
nocturnal behavior. Detailed analyses of nocturnal behavior have only
been conducted for very prominent ungulates such as giraffes, elephants,
or livestock, and the nocturnal rhythms exhibited by many ungulates
remain unknown. In the present study, the nocturnal rhythms of 192
individuals of 18 ungulate species from 20 European zoos are studied
with respect to the behavioral positions standing, lying - head up, and
lying - head down (the typical REM sleep position). Differences between
species of the orders Perissodactyla and Cetartiodactyla, as well as
between individuals of different age were found. However, no differences
with respect to the sex were seen. Most species showed a significant
increase in the proportion of lying during the night. In addition, the
time between two events of “lying down” was studied in detail. A high
degree of rhythmicity with respect to this quantity was found in all
species. The proportion of lying in such a period was greater in
Cetartidactyla than in Perissodactyla, and greater in juveniles than in
adults.