Presence Of Manatees Research Articles

THE ANTILLEAN MANATEE IN THE NORTH OF MARACAIBO LAKE (VENEZUELA): DISTRIBUTION, AND CONSERVATION ISSUES

In Venezuela, Antillean manatees (Trichechus manatus manatus) have declined mainly due to habitat loss and degradation, but other threats to the species persist. The objective of this work was to investigate the manatee distribution and conservation issues in Maracaibo Lake, Venezuela. Aiming to collect evidence on manatee presence, we conducted 404.14 hours of boat-based surveys and observations from the shore during 2003, 2004, 2009, and 2010. Environmental parameters were collected in areas where manatees were observed including pH, temperature, dissolved oxygen, salinity, transparency, and depth. Also, we recorded plants or algae that could serve as potential food for manatees. We developed 96 informal and opportunistic talks with local fishermen, to gather information about manatee occurrence, boat traffic, and people’s perception of the species. Finally, we reviewed published and unpublished documents containing information on manatees in Maracaibo Lake. The resulting database contains information on 39 sightings and 13 reports of dead manatees. The known causes of death were poaching, vandalism, boat collision, and entanglement in fishing nets. The Maracaibo Lake offers many suitable habitats for manatees, but also faces a wide array of conservation problems that represent critical threats to this endangered subspecies. Long-term monitoring of this population and potential sources of mortality is highly needed.

Manatees in Zoological Parks throughout the World: History, State, and Welfare.

The order Sirenia comprises several species of manatees and one species of dugong. These popular marine mammals are relatively recent acquisitions to zoological parks throughout the world. As far as we know, there are less than 200 manatees, mostly American, a few African, and ever less Amazonian, currently in zoological parks. American manatees are predominantly found in zoos in Europe, North America, and in some Asian countries, while African ones are present exclusively in Asian zoos. The living conditions of captive manatees differ considerably from zoo to zoo (i.e., numbers, sex ratio, outdoor vs. indoor habitats, complex vs. simple habitats). Most research on manatee behaviour has been relatively recent, and studies on cognition, sociality, and ecology have a significant impact on our perception of manatee needs and management, with wider implications for their welfare. In the wild, manatees demonstrated various cognitive capacities; spatial memory and learning abilities play an important role in their daily life in a complex and dynamic environment. Furthermore, there is evidence that these mammals are more social animals than expected. Individuals show various personality traits on the boldness-shyness continuum and their sociality varies. All those parameters are important in terms of animal welfare. Several behavioural studies showed that standardized enrichment programs benefit and ensure the welfare of captive zoo animals. However, obtaining accurate information on the presence of manatees in zoos, living conditions, management, and consequently welfare remains challenging. This study examines the current knowledge on manatee behaviour and cognition and then discusses different approaches to improving the welfare of this charismatic marine mammal in zoological parks.

Occurrence of the Endangered Antillean manatee Trichechus manatus manatus in a marine protected area, Isla de la Juventud, Cuba

AbstractThe Antillean manatee Trichechus manatus manatus is categorized as Endangered on the IUCN Red List but little is known about the status of the species in Cuba. Marine protected areas can contribute to manatee conservation in Cuba but the effectiveness of these areas may be jeopardized by a lack of information regarding appropriate design and management. We developed an index of manatee occurrence in the Fauna Refuge Ciénaga de Lanier, Isla de la Juventud, to assess patterns of manatee use in the reserve. We completed 26 field trips during November 2007–October 2013, with a total of 147 survey days. Manatee presence was detected on 47% of survey days and in 96% of field trips; 133 individuals were recorded in 93 sightings. The index of manatee occurrence varied between trips, suggesting a discontinuous use of the area. The mean group size was 1.4 individuals (range 1–5), and calves were observed in 13% of sightings. Observations of manatee behaviour, occurrence and habitat characteristics indicate the importance of the study area as a resting place, refuge and source of fresh water. We recommend that manatee protection be strengthened to avoid human-related mortality and to ensure that the habitats that provide critical resources are given special consideration in future management plans.

Estado del manatí del Amazonas <em>(Trichechus inunguis)</em> en la Reserva Cuyabeno, Ecuador

Los manatíes amazónicos viven en ríos de aguas negras y lagunas de la Cuenca Amazónica. La primera información sobre la distribución y el estado de conservación de manatíes en la Reserva Cuyabeno proviene de un estudio realizado en 1983 por Timm y otros [1]. Ellos concluyeron que el manatí se puede extinguir en la próxima década. En este artículo se presenta los resultados de observaciones y entrevistas realizados desde 1996 a 1999, trece años después. Durante 127 días de monitoreo del Delfín Amazónico (Inia geoffrensis) en el habitat del manatí a lo largo de ríos y lagunas de agua negra, se observó durante 456 horas. Adicionalmente se realizaron monitoreos dirigidos a manatíes en las Lagunas Grandes de Cuyabeno. Entrevistas con guías de turismo, guardaparques e indígenas dan una lista completa de avistamientos de manatíes, su distribución y la situación de conservación. La abundancia relativa estimada en el Río Cuyabeno es de 0,01 animales/hora de esfuerzo y aün menor en el río Lagartococha con 0,007 animales/ hora de esfuerzo. Las poblaciones en el rio Lagartococha parecen severamente reducidas. En ambos ríos la caza entre 1995 y 1998 continuó. A pesar de la protección legal se mataron al menos 16 animales dentro de la Reserva Cuyabeno, por ende el hecho de vivir en una area protegida no necesariamente significa la sobrevivencia de la especie.

Distribution and Conservation of the West Indian Manatee (Trichechus manatus Manatus) in the Catazajá Wetlands of Northeast Chiapas, México

Tropical coastal wetlands have a rich biodiversity, a restricted geographic distribution and are a prime habitat for manatees in the regions where they occur in the Neotropics. Human pressures affect the persistence of tropical wetland ecosystems and hence of manatees. In the continental Neotropics, the West Indian manatee ( Trichechus manatus) is represented in Mexico by the subspecies T. m. manatus. Lack of information regarding the current distribution of manatees in Mexico hampers conservation approaches of this marine mammal. In this paper we present information on a survey of a population of manatees found in the Catazajá wetlands (ca 60,000ha) in northeast Chiapas, Mexico. We additionally report on manatee conservation efforts spanning seven years aimed at involving the participation of local rural communities. Systematic surveys for the presence of manatees were conducted between Feb-Nov, 2007 by sightings along sampling transects in waterways, recording of manatee presence as evidenced by recently browsed aquatic vegetation, presence of stranded individuals and presence of deceased manatees. Additionally, some records of manatee presence underwater were obtained by using a side-scan sonar system. Lastly, interviews with 120 individuals from 10 local communities also yielded information on manatee presence in the wetland system. A map of the study area divided into a grid of 50 ha cells was used to plot and quantify the records of manatee presence obtained with the above procedures. Results indicated presence of manatees in 11% (ca 4,850 ha) of the 50 ha cells into which the study area was divided. Records indicate presence of manatees throughout the wetland, but with concentration in particular sectors. Involvement of local communities in manatee conservation has resulted in designating the Catazajá wetlands as a natural protected area.

Background noise reduction of manatee vocalizations

The West Indian manatee (Trichechus manatus latirostris) has become an endangered species in the United States partly because of an increase in the number of collisions with boats. A device to alert boaters of the presence of manatees is desired. Previous research has shown that background noise limits the detection range (which is critical for practical implementation). By improving the signal-to-noise ratio of the vocalization signal, it is possible to extend the detection range. The finite impulse response (FIR) structure of the adaptive line enhancer (ALE) can detect and track narrow-band signals buried in broadband noise. In this paper, a constrained infinite impulse response (IIR) ALE, called a feedback ALE (FALE), is implemented to reduce the background noise. In addition, a bandpass filter is used as a baseline for comparison. A library consisting of 100 manatee calls spanning ten different signal categories is used to evaluate the performance of the bandpass filter, FIR-ALE, and FALE. The results show that the FALE is capable of reducing background noise by about 6.0 and 21.4 dB better than that of the FIR-ALE and bandpass filter, respectively, when the signal-to-noise ratio (SNR) of the original manatee call is −5 dB.

Development of predictive models to explain the distribution of the West Indian manatee Trichechus manatus in tropical watercourses

Logistic regressions were used to study the relationship between habitat variables and the use of tropical watercourses by the West Indian manatee Trichechus manatus at Northeastern Costa Rica and Southern Nicaragua. Presence of manatees in watercourses was assessed through direct and reported sightings of individuals and feeding signs on aquatic vegetation. Indirect methods provided good approximations to the actual distribution that could not have been achieved through direct observations or aerial surveys. Best multivariate models showed that manatees were most present in watercourses that presented abundant aquatic vegetation, warm, and clear waters, high forest cover, and are wider than those where the species is absent. Although habitat variables that explain habitat use of manatees differed for the two sectors found within the study area, manatees preferred lagoons to other watercourses in both areas. These findings point to forest clearing on the shores as a threat for manatee conservation. Habitat variables are excellent predictors of manatee presence, and predictive models as those developed in this study can help assess potential distribution of manatees in areas where this information is lacking as well as to assist identify potential reintroduction areas.