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Study of underwater behaviour of Amazonian manatees

1. Member


Dr. Mumi Kikuchi (wildlife Research Center of Kyoto University)


Diogo A de souza (INPA) Dr. Vera da Silva (INPA)

2. Background

Sirenians (manatees and dugong) are the only extant herbivorous aquatic mammals. Despite utilizing coastal shallow habitats, much remains unknown about their behaviour, especially for the Amazonian manatees (Trichechus inunguis) that is endemic to the Amazon region. There are no reliable population estimates available, although numbers are almost certainly lower than historical figures due to centuries of hunting (IUCN Red List). The Amazonian manatee is listed as Vulnerable in the IUCN Red List.

3. Objective, methods and expected results

We are adopting the soft- releasing program, the captive-raised manatees can adapt to the natural environment in the semi-captive region before releasing into the wild. The overall objective is to monitor the adaptation of released manatees to the wild in order to improve the rehabilitation program. One of the vital questions about released manatees is when they are feeding once released. In this study, we record the manatee’s feeding sounds using the animal-born sound reorder. We aim to detect the feeding events from the recorded sound in order to understand when, what kind of plants, and how much the manatee eat after releasing into the wild.

4. Contribution for the Field Museum

This study will improve the releasing program for the captive-raised Amazonian manatees by assessing the adaptation to the wild using animal-borne devices. We investigate how released manatees accommodate to the wild by comparing behaviors recorded by the animal-born data-loggers, such as feeding behaviour, breathing frequency, resting duration and timing, between captivity and the released.

5. Inpact and contribution for human resource development

This collaboration allows sharing of information among the Japan and Brazil researchers regarding the new methods and developing technique. And we hope the new technique will be applied to the various study in another area or country. In the manatee-releasing program, we enlighten the people living in the releasing area about the manatee fact. This activity will spread the awareness of environmental protection on a local level, which is the most important for the conservation of endangered Amazonian manatees.

Figure1. The Amazonian manatee in the semi-captive lake, Amazon river.

Figure2. The released Amazonian manatees with animal-born data loggers. The data-loggers were attached by suction-cup-tags.