Manatee temporal trends data used in analysis.

Many marine mammals exhibit diel trends in vocal production, which can provide information on habitat use and behavioral activity. In Belize, Antillean manatees (Trichechus manatus manatus) commonly inhabit small depressions in the substrate or deep-water coves known as “resting holes”. Determining if manatees exhibit diel temporal trends in their call production rate and call types between microhabitats can provide insights into their diurnal and nocturnal activity patterns. Here, we investigate the diel vocalization patterns of wild Antillean manatees in two adjacent resting holes off of St. George’s Caye, Belize. Recordings of manatees were made using a bottom-mounted hydrophone located near a reef barrier reef for nine days in July of 2017 and ten days in January of 2018. To explore if and how manatee acoustic activity differs between sites, we compared the number of calls per hour, the number of manatee positive hours, the number of tonal and atonal sounds, and the number of boats detected across sites. A total of 370 hours of acoustic recordings were analyzed resulting in the detection of 3,262 calls. There were no significant differences in the number of manatee calls produced per hour between sites. The average number of calls produced by manatees decreased over the course of several days. The proportion of tonal calls decreased with hours after sunset and increased in boat presence. These results suggest manatees in this region may exhibit different diel activity patterns which appear to be influenced by the characteristics of the environment. These findings can support ongoing conservation and management efforts to safeguard species in Belize.许多海洋哺乳动物的发声活动呈现昼夜节律特征，此类节律可为探究其栖息地利用模式与行为活动提供科学依据。在伯利兹海域，安的列斯海牛（Antillean manatee，学名：Trichechus manatus manatus）常栖息于底质小型凹陷区域或被称为“休憩洞”的深水湾内。明确海牛在不同微生境下的发声速率与发声类型是否存在昼夜时间节律，可帮助解析其昼行与夜行活动模式。本研究针对伯利兹圣乔治礁（St. George’s Caye）附近两处相邻休憩洞内的野生安的列斯海牛，探究其昼夜发声模式。本研究于2017年7月与2018年1月分别开展为期9天与10天的声学数据采集，使用布放于近堡礁区域的海底水听器记录海牛发声信号。为探究不同休憩洞内海牛声学活动是否存在差异及差异机制，本研究对比了各点位的单小时发声次数、海牛发声有效小时数、有声调与无声调发声的数量，以及各点位检测到的船只数量。本研究共分析370小时的声学录音数据，总计识别出3262次海牛发声。不同休憩洞的单小时海牛发声次数无显著差异。在整个观测周期内，海牛的平均每小时发声量随天数推移逐渐降低。有声调发声的占比随日落后时长增加而降低，且随船只出现频次增加而升高。上述结果表明，该区域的安的列斯海牛可能存在独特的昼夜活动模式，且该模式似乎受环境特征的调控。本研究结果可为伯利兹海域当前开展的海牛物种保护与管理工作提供科学支撑。