Despite increasing interest in the behavior of zoo animals, studies of nocturnal behavior of zoo animals are limited. In this study, we investigated the relationship between parturition, season, and the sleep-related behaviors in captive reticulated giraffes to better understand the nocturnal life in giraffes. The subjects were two adult reticulated giraffes living in Kyoto City Zoo, Japan. Observations were made via an infrared camera that was mounted in the indoor enclosure between June 2007 and August 2009. We analyzed video clips that were recorded between 16:30 and 09:00 the next morning, over a total of 199 days. Sleep-related behaviors were classified into two categories based on the posture of the giraffes; recumbent posture and paradoxical sleep. We also recorded the laterality of recumbent posture, which was coded based on the direction of the legs against the torso (right or left). Seasonal differences in sleep behaviors between summer and winter were observed in both individuals. They tended to start to lie down earlier in the winter than in the summer. Parturition also affected the behaviors as both individuals decreased the behaviors before and after the parturition of the female. Additionally, the female lay on her left side less frequently than her right when resuming a recumbent posture in the pre-parturition period, while such laterality was not observed in the baseline and post-parturition period. These results suggested that season and parturition are important factors for determining the sleep-related behaviors in giraffes. Further studies are needed to understand how these changes in sleep affect other welfare parameters.

中文翻译：

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动物园长颈鹿（Giraffa camelopardalis reticulata）的睡眠相关行为：季节和分娩的基本特征和影响

尽管人们对动物园动物的行为越来越感兴趣，但对动物园动物夜间行为的研究却很有限。在这项研究中，我们调查了圈养网纹长颈鹿的分娩、季节和睡眠相关行为之间的关系，以更好地了解长颈鹿的夜间生活。研究对象是生活在日本京都市动物园的两只成年网纹长颈鹿。观察是通过 2007 年 6 月至 2009 年 8 月间安装在室内围栏内的红外摄像机进行的。我们分析了在 16:30 至第二天早上 09:00 之间录制的视频剪辑，共计 199 天。根据长颈鹿的姿势，与睡眠相关的行为分为两类；卧姿和矛盾的睡眠。我们还记录了卧姿的偏侧性，这是根据腿靠在躯干上的方向（右侧或左侧）进行编码的。在两个个体中都观察到了夏季和冬季睡眠行为的季节性差异。他们往往在冬天比夏天更早开始躺下。分娩也影响行为，因为两个人都减少了女性分娩前后的行为。此外，女性在产前恢复卧姿时左侧卧位的频率低于右侧，而在基线和产后期间未观察到这种侧卧。这些结果表明，季节和分娩是决定长颈鹿睡眠相关行为的重要因素。需要进一步研究以了解这些睡眠变化如何影响其他福利参数。