Manatees display diel trends in acoustic activity at two microhabitats in Belize

Abstract

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.

Acoustic estimation of the manatee population and classification of call categories using artificial intelligence

“…Intriguingly, specific vocalizations among manatees exhibit cross-species and subspecies occurrence. As per Reyes-Arias et al (2023), within the geographic diversity in manatee vocal repertoires, specific calls are consistent across populations, subspecies, and diverse geographic locations. The study compared the vocalizations of wild West Indian manatees from Florida (Trichechus manatus latirostris) and Antillean manatees (Trichechus manatus manatus) from Belize and Panama.…”

Ultrasonic vocalisation rate tracks the diurnal pattern of activity in winter phenotype Djungarian hamsters (Phodopus sungorus)

“…Timing of vocalisation during wake is an important contextual cue used to understand its functions. Vocalisation is often associated with an animal’s active period (Walsh & Inglis 1989 ; Hammerschmidt et al 1994 ; Catchpole and Slater 2003 ; Brady et al 2023 ) and therefore can be sensitive to changes in zeitgebers, for example light’s effects on bird song timing (Da Silva et al 2014 ; Bruni et al 2014 ). Concentration of vocalisations at dawn and dusk is a common feature observed in insects, amphibians, birds, fish and mammals (Farina and Ceraulo 2017 ).…”