RESUMO
Geographic variation in the vocal behavior of manatees has been reported but is largely unexplored. Vocalizations of wild West Indian manatees (Trichechus manatus) were recorded with hydrophones in Florida from Florida manatees (Trichechus manatus latirostris), and in Belize and Panama from Antillean manatees (Trichechus manatus manatus) to determine if calls varied between subspecies and geographic regions. Calls were visually classified into five categories: squeaks, high squeaks, squeals, squeak-squeals, and chirps. From these five categories, only three call types (squeaks, high squeaks and squeals) were observed in all three populations. Six parameters from the temporal and frequency domains were measured from the fundamental frequency of 2878 manatee vocalizations. A repeated measures PERMANOVA found significant differences for squeaks and high squeaks between each geographic location and for squeals between Belize and Florida. Almost all measured frequency and temporal parameters of manatee vocalizations differed between and within subspecies. Variables that may have influenced the variation observed may be related to sex, body size, habitat and/or other factors. Our findings provide critical information of manatee calls for wildlife monitoring and highlight the need for further study of the vocal behavior of manatees throughout their range.
Assuntos
Trichechus manatus , Vocalização Animal , Trichechus manatus/fisiologia , Animais , Tamanho Corporal , América , Oceano Atlântico , EcossistemaRESUMO
Studies on the cognitive abilities of manatees are limited despite their importance for the environmental enrichment and welfare of individuals in captivity and the understanding of manatee behaviour in the wild. Our study analyses how the presence of new stimuli and their association with food may have changed the behaviour of an Antillean manatee called Daniel. First, Daniel was observed in the absence of stimuli and subsequently, in step two, presented with the presence of four different geometrical shapes. During step three, we trained Daniel to eat from the square, while in step four he was presented with the four shapes without food. The behaviour and interaction of the manatee with the square increased considerably. We observed that three and twelve months after training the manatee still chose the square and displayed behaviours toward this specific shape. This study allowed us to formally demonstrate the ability of manatees to associate visual cues with food and increase activity with environmental and occupational devices. Our results open up new perspectives for behavioural studies on manatees, in particular those associated with cognition, management and welfare in captivity.
Il existe peu d'information à propos des capacités cognitives des lamantins et comment elles peuvent permettre d'améliorer le bien-être de ces animaux en captivité. Notre étude analyse comment la présence de nouveaux stimuli et leur association avec de la nourriture peut changer le comportement d'un lamantin antillais nommé Daniel. Premièrement Daniel a été observé en absence de stimuli puis ensuite en présence de quatre formes géométriques différentes. Dans un troisième temps Daniel fût entrainé à manger en association avec une forme, le carré. Dans un quatrième temps, les quatre formes lui sont proposées mais sans nourriture associée. Les comportements différents et les interactions du lamantin avec le carré augmentent considérablement après cet aprentissage. L'expèrience est retentée 3 mois et 12 mois plus tard, sans renforcement, et Daniel continue de choisir le carré avec des comportements particuliers liés à cette forme. Cette étude permet de montrer de manière formelle la capacité des lamantins à associer la possibilité de nourriture avec des formes visuelles, et aussi la possibilité d'augmenter son activité avec des dispositifs environnementaux et occupationnels. Ces résultats offrent de nouvelles perspectives pour l'étude du comportement des lamantins, en particulier liées à la cognition, à leur gestion et à leur bien-être en captivité.
Assuntos
Comportamento Animal/fisiologia , Aprendizagem/fisiologia , Trichechus manatus/fisiologia , Animais , MasculinoRESUMO
This work presents a methodology to automatically detect and identify manatee vocalizations in continuous passive acoustic underwater recordings. Given that vocalizations of each manatee present a slightly different frequency content, it is possible to identify individuals using a non-invasive acoustic approach. The recordings are processed in four stages, including detection, denoising, classification, and manatee counting and identification by vocalization clustering. The main contribution of this work is considering the vocalization spectrogram as an image (i.e., two-dimensional pattern) and representing it in terms of principal component analysis coefficients that feed a clustering approach. A performance study is carried out for each stage of the scheme. The methodology is tested to analyze three years of recordings from two wetlands in Panama to support ongoing efforts to estimate the manatee population.
Assuntos
Trichechus manatus/fisiologia , Vocalização Animal , Animais , Panamá , Áreas AlagadasRESUMO
The West Indian (Trichechus manatus) and Amazonian (T. inunguis) manatees have a sympatric occurrence at the mouth of the Amazon River. A result of this interspecific encounter is the occurrence of hybrids, which are frequently found along the coasts of Amapá state in Brazil, French Guiana and Guyana. Here we present new genetic evidence indicating the occurrence of a hybrid swarm along the Guianas Shield coastline, which is an interspecific hybrid zone that also separates T. manatus populations located east (Brazil) and west (Caribbean, Gulf of Mexico, Florida and Antilles). In addition, we suggest that this hybrid population occupies a peculiar mangrove-rich environment under strong influence of the Amazon River plume, which requires an independent management and should be considered a special conservation area.
Assuntos
Variação Genética/genética , Hibridização Genética , Especificidade da Espécie , Trichechus inunguis/genética , Trichechus manatus/genética , Animais , Teorema de Bayes , Brasil , Região do Caribe , Guiana , Filogenia , Dinâmica Populacional , Rios , Trichechus inunguis/fisiologia , Trichechus manatus/fisiologiaRESUMO
West Indian (Trichechus manatus) and Amazonian (T. inunguis) manatees are vocal mammals, with most sounds produced for communication between mothers and calves. While their hearing and vocalizations have been well studied, the actual mechanism of sound production is unknown. Acoustical recordings and anatomical examination were used to determine the source of sound generation. Recordings were performed on live captive manatees from Puerto Rico, Cuba and Colombia (T. manatus) and from Peru (T. inunguis) to determine focal points of sound production. The manatees were recorded using two directional hydrophones placed on the throat and nasal region and an Edirol-R44 digital recorder. The average sound intensity level was analyzed to evaluate the sound source with a T test: paired two sample for means. Anatomical examinations were conducted on six T. manatus carcasses from Florida and Puerto Rico. During necropsies, the larynx, trachea, and nasal areas were dissected, with particular focus on identifying musculature and soft tissues capable of vibrating or constricting the airway. From the recordings we found that the acoustical intensity was significant (P < 0.0001) for both the individuals and the pooled manatees in the ventral throat region compared to the nasal region. From the dissection we found two raised areas of tissue in the lateral walls of the manatee's laryngeal lumen that are consistent with mammalian vocal folds. They oppose each other and may be able to regulate airflow between them when they are adducted or abducted by muscular control of arytenoid cartilages. Acoustic and anatomical evidence taken together suggest vocal folds as the mechanism for sound production in manatees.
Assuntos
Laringe/anatomia & histologia , Traqueia/anatomia & histologia , Trichechus inunguis/anatomia & histologia , Trichechus manatus/anatomia & histologia , Vocalização Animal/fisiologia , Animais , Feminino , Índia , Laringe/fisiologia , Masculino , Som , América do Sul , Traqueia/fisiologia , Trichechus inunguis/fisiologia , Trichechus manatus/fisiologiaRESUMO
The Antillean manatee (Trichechus manatus manatus), a subspecies of the West Indian manatee, inhabits fresh, brackish, and warm coastal waters distributed along the eastern border of Central America, the northern coast of South America, and throughout the Wider Caribbean Region. Threatened primarily by human encroachment, poaching, and habitat degradation, Antillean manatees are listed as endangered by the International Union for the Conservation of Nature. The impact of disease on population viability remains unknown in spite of concerns surrounding the species' ability to rebound from a population crash should an epizootic occur. To gain insight on the baseline health of this subspecies, a total of 191 blood samples were collected opportunistically from wild Antillean manatees in Belize between 1997 and 2009. Hematologic and biochemical reference intervals were established, and antibody prevalence to eight pathogens with zoonotic potential was determined. Age was found to be a significant factor of variation in mean blood values, whereas sex, capture site, and season contributed less to overall differences in parameter values. Negative antibody titers were reported for all pathogens surveyed except for Leptospira bratislava, L. canicola, and L. icterohemorrhagiae, Toxoplasma gondii, and morbillivirus. As part of comprehensive health assessment in manatees from Belize, this study will serve as a benchmark aiding in early disease detection and in the discernment of important epidemiologic patterns in the manatees of this region. Additionally, it will provide some of the initial tools to explore the broader application of manatees as sentinel species of nearshore ecosystem health.
Assuntos
Trichechus manatus/sangue , Trichechus manatus/fisiologia , Trichechus manatus/parasitologia , Animais , Animais Selvagens/sangue , Belize , Conservação dos Recursos Naturais , Ecossistema , Feminino , Geografia , Leptospira/metabolismo , Masculino , Morbillivirus/metabolismo , Valores de Referência , Estudos Soroepidemiológicos , Toxoplasma/metabolismoRESUMO
Phylogeographic patterns and sex-biased dispersal were studied in riverine populations of West Indian (Trichechus manatus) and Amazonian manatees (T. inunguis) in South America, using 410bp D-loop (Control Region, Mitochondrial DNA) sequences and 15 nuclear microsatellite loci. This multi-locus approach was key to disentangle complex patterns of gene flow among populations. D-loop analyses revealed population structuring among all Colombian rivers for T. manatus, while microsatellite data suggested no structure. Two main populations of T. inunguis separating the Colombian and Peruvian Amazon were supported by analysis of the D-loop and microsatellite data. Overall, we provide molecular evidence for differences in dispersal patterns between sexes, demonstrating male-biased gene flow dispersal in riverine manatees. These results are in contrast with previously reported levels of population structure shown by microsatellite data in marine manatee populations, revealing low habitat restrictions to gene flow in riverine habitats, and more significant dispersal limitations for males in marine environments.