First characterization of vocalizations and passive acoustic monitoring of the vulnerable African manatee (<i>Trichechus senegalensis</i>)

Rycyk, Athena M.; Factheu, Clinton; Ramos, Eric A.; Brady, Beth; Kikuchi, Mumi; Nations, Hannah F.; Kapfer, Karianne; Hampton, Cecilia M.; Garcia, Emily R.; Kamla, Aristide Takoukam

doi:10.1121/10.0006734

Cited by 8 publications

(12 citation statements)

References 40 publications

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“…Currently, there are no published studies investigating if there are differences in frequency and temporal parameters among calf species. A few studies compared vocalizations between West Indian 33 and African manatee species 34 and noted significant overlap in frequency and temporal parameters. Although these differences were observed, it is unclear if calls from the West Indian and African manatees were obtained from adults and/or calves.…”

Section: Introductionmentioning

confidence: 99%

Manatee calf call contour and acoustic structure varies by species and body size

Brady

Ramos

May‐Collado

et al. 2022

Sci Rep

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Vocal activity and signal characteristics of mammals are driven by several factors that result in both stability and plasticity over multiple time scales. All three extant species of manatee communicate with several calls that are especially important for maintaining contact between cows and calves. Determining if calf calls differ across manatee species will provide insights into the evolution of species-specific acoustic communication traits. We investigated the interspecific differences in the vocalizations of calves of Amazonian manatees (Trichechus inunguis) and the two subspecies of the West Indian manatee (T. manatus). Vocalizations of individual calves were recorded in rehabilitation centers in Brazil, Puerto Rico, the United States, and Mexico. The acoustic structure of calls produced by manatee calves varied between species and with body size. Amazonian manatee calves produced shorter calls with multiple notes at higher frequency while West Indian calves produced modulated calls that were lower in frequency and longer in duration. Smaller West Indian calves produced frequency modulated, hill-shaped calls that flattened with an increase in body length. Our results provide evidence for divergence in the ontogeny of vocalizations across T. manatus and T. inunguis and suggest variation in body size contributed to the evolution of differences in the characteristics of their calls.

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Section: Introductionmentioning

confidence: 99%

Manatee calf call contour and acoustic structure varies by species and body size

Brady

Ramos

May‐Collado

et al. 2022

Sci Rep

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“…All surveys were conducted between 06:00 and 10:00 AM, a timeframe during which manatees are more likely to be visually spotted in Lake Ossa (Takoukam Kamla, 2012). According to Rycyk et al (2021), African manatees in Lake Ossa seem to be more active out of daylight hours, presumably in avoidance of human presence. For all survey methods, detections were scored as presence/absence for each one-hour survey.…”

Section: Experimental Designmentioning

confidence: 99%

“…In addition, manatees produce a variety of vocalizations including squeaks, screeches, whines, and trills (Umeed et al, 2018;Brady et al, 2020;Baotic et al, 2022) shown to be important for their underwater communication and emitted across various behavioral states (Bengtson and Fitzgerald, 1985;O'Shea and Poche, 2006;Brady et al, 2021). Passive acoustics have been used in many studies to monitor manatees and have yielded up to 100% detection frequencies (LaCommare et al, 2008;Kikuchi et al, 2013;Rivera Chavarria et al, 2015;Rycyk et al, 2021;Rycyk et al, 2022). While the above methodologies have been used to monitor other species of manatee (Florida manatees: Rycyk et al, 2022;Antillean manatees: Ramos et al, 2020), they have been rarely implemented with African manatees.…”

Section: Introductionmentioning

confidence: 99%

“…While the above methodologies have been used to monitor other species of manatee (Florida manatees: Rycyk et al, 2022;Antillean manatees: Ramos et al, 2020), they have been rarely implemented with African manatees. Rycyk et al (2021) deployed passive acoustic recorders in Lake Ossa in 2020 for two, 3-day periods, resulting in the detection of thousands of vocalizations and enabling the first characterization of African manatee calls; the authors found that African manatee vocalizations are similar to those of other manatee species, with mean fundamental frequency of 4.65 kHz and average duration of 0.181s. Finally, Takoukam Kamla (personal communication) conducted sporadic sonar detections.…”

Section: Introductionmentioning

confidence: 99%

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Acoustic methods improve the detection of the endangered African manatee

Factheu

Rycyk²,

Kekeunou³

et al. 2023

Front. Mar. Sci.

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The African manatee (Trichechus senegalensis) is an elusive, data-deficient, and endangered species which inhabits marine and freshwater systems throughout Western and Central Africa. A major challenge in understanding the species ecology and distribution is the difficulty in detecting it using traditional visual surveys. The recent invasion of Giant Salvinia (Salvinia molesta) at the most important site for the species in Cameroon further limits their detectability and may restrict their movements and habitat use. To investigate methods’ effectiveness in detecting African manatees, we conducted monthly vessel surveys from which visual point scans, 360° sonar scans, and passive acoustic monitoring were conducted simultaneously at ten locations and over 12 months in Lake Ossa, Cameroon. Manatee detection frequency was calculated for each method and the influence of some environmental conditions on the methods’ effectiveness and manatee detection likelihood was assessed by fitting a binary logistic regression to our data. Detection frequencies were significantly different between methods (p < 0.01) with passive acoustics being the most successful (24.17%; n = 120), followed by the 360° sonar scan (11.67%; n = 120), and the visual point scan (3.33%; n = 120). The likelihood of detecting manatees in Lake Ossa was significantly influenced by water depth (p = 0.02) and transparency (p < 0.01). It was more likely to detect manatees in shallower water depths and higher water transparency. Passive acoustic detections were more effective in uninvaded areas of the Lake. We recommend using passive acoustics to enhance African manatee detections in future surveys.

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“…Studies suggest that all Sirenian species make squeaks (referred to as chirp-squeaks in dugongs) that vary slightly in their range of f 0 (Anderson & Barclay, 1995;Nowacek et al, 2003;Rycyk et al, 2021;Sousa-Lima et al, 2008). West Indian manatees, African manatees, and dugongs produce vocalizations with overlapping f 0 ranges from 0.5 to 5 kHz (Anderson & Barclay, 1995;Nowacek et al, 2003;Rycyk et al, 2021), whereas Amazonian manatees produce calls with a higher f 0 at 1.6 to 8 kHz (Sousa-Lima et al, 2008). The other common vocalization described in the dugong and manatees is the atonal vocalization.…”

Section: Structure and Function Of Vocalizationsmentioning

confidence: 99%

Elephants and Sirenians: A Comparative Review across Related Taxa in Regard to Learned Vocal Behavior

Baotic¹,

Brady²,

Ramos³

et al. 2022

CCBR

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Vocal production learning is the ability to modify a vocal output in response to auditory experience. It is essential for human speech production and language acquisition. Vocal learning evolved independently several times in vertebrates, indicating evolutionary pressure in favor of this trait. This enables cross-species comparative analysis to be used to test evolutionary hypotheses. Humans share this ability with a versatile but limited group of species: songbirds, parrots and hummingbirds, bats, cetaceans, seals, and elephants. Although case studies demonstrate that African savanna and Asian elephants are capable of heterospecific imitation, including imitation of human words, our understanding of both the underlying mechanisms and the adaptive relevance within the elephant's natural communication system is limited.Even though comparing phylogenetically distant species is intriguing, it is also worthwhile to investigate whether and to what extent learned vocal behavior is apparent in species phylogenetically close to an established vocal learner. For elephants, this entails determining whether their living relatives share their special ability for (complex) vocal learning.In this review, we address vocal learning in Elephantidea and Sirenia, sister groups within the Paenungulata. So far, no research has been done on vocal learning in Sirenians. Because of their aquatic lifestyle, vocalization structure, and evolutionary relationship to elephants, we believe Sirenians are a particularly interesting group to study. This review covers the most important acoustic aspects related to vocal learning in elephants, manatees, and dugongs, as well as knowledge gaps that must be filled for one to fully comprehend why vocal learning evolved (or did not) in these distinctive but phylogenetically related taxa.

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First characterization of vocalizations and passive acoustic monitoring of the vulnerable African manatee (Trichechus senegalensis)

Cited by 8 publications

References 40 publications

Manatee calf call contour and acoustic structure varies by species and body size

Manatee calf call contour and acoustic structure varies by species and body size

Acoustic methods improve the detection of the endangered African manatee

Elephants and Sirenians: A Comparative Review across Related Taxa in Regard to Learned Vocal Behavior

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