Manatee Chat Project

Manatee acoustic communication has not been studied extensively because it has been believed that manatees have a very limited communication system, which acts mainly as a contact call between a mother and calf. This project will investigate the form and function of manatee vocalizations, and it will allow us to learn more about what signals manatees produce, what potential function they might serve, and what differences individual manatee calls have.

The project's overall goal is to analyze the acoustic (and later video) data sets with the help of citizen scientists. Part of this analysis will be used to train a deep learning system to identify and classify manatee calls. This is phase one of the project in which the citizen scientists are asked to identify and count manatee calls.

Florida Manatee

Florida Manatee (Trichechus manatus latirostris) is a part of lineage of sirenians that are 50 million years old. While there is some evidence of 35 sirenian species existing over this period of time, today we only have four species left that belong to two families (Dugongidae and Trichechidae). Trichechus manatus latirostris is Florida subspecies and is a part of this project. Manatees feed solely on aquatic vegetation and have no natural predators apart from humans. According to the last aerial survey, Florida currently has 6620 manatees. Even though manatees were recently downgraded from Endangered to Threatened status, they face many challenges, as many die from boat related injuries, toxic algae blooms, entanglements, and cold stress.

Manatee Calls

Manatees have good hearing with an overall hearing range between 500 Hz and 38,000 Hz. The range of the vocalizations is between 3 and 20 kHz (Reep & Bonde, 2006). Manatees are very vocal and produce at least several different types of calls (Umeed et al., 2017; Mann et al., 2006). Although it has been proposed that the main function of manatee vocalizations is to serve as the contact calls between a mother and calf (O'shea and Poché Jr, 2006), there is at least some anecdotal evidence that unrelated manatees might also use calls for social purposes. At this stage, we simply ask for your help to determine if there is a manatee call in the sound file and also to count how many calls you hear in the audio file and see on the spectrogram. Once you start working on this project, you will be amazed by the diversity of calls produced, and you'll discover how manatees appear to call back in response to certain calls.Manatees have somewhat unusual calls because many people expect some sort of low frequency grunts based on the manatee’s size, but the actual calls sound more like bird chirps.

Other Sounds

The underwater environment is rarely silent. Since the recordings were made at the Lowry Park Zoo Manatee Hospital and Rehabilitation Center you will hear many other sounds (learn more in the Project Tutorial and the Field Guide ). You will hear the following: mastication (chewing) sounds that could help to identify the feeding events, mechanical sounds from the recording equipment, filter sounds, some other sounds when manatees rub against the underwater hydrophone, and in some cases you will even hear people talking in the manatee exhibit area.

Data Collection Site

The data was collected over a period of several years at the Lowry Park Zoo (now Zoo Tampa at Lowry Park) Manatee Hospital, Tampa, Florida, USA. Zoo's David A. Straz, Jr. Manatee Critical Care Center is one of the most important manatee rehabilitation facilities in Florida. It has been taking care of sick, injured, and orphaned manatees for more than two decades. Over 20 manatees (males and females) were observed and recorded, their ages differed from just few months old to over twenty years old. Our data sets included both video and audio, but phase one of this project will only include audio data.

Update 03/31/2020: A New Freshwater Dataset Added

Image by Jay Dodge. Manatees at Blue Springs in Orange City, FL

We have added a new dataset graciously shared with us by the Sirenian International nonprofit organization. Their mission is to promote the conservation of manatees and dugong populations around the world through research, education, and inter-cultural collaboration. Please check their website here to learn more. These recordings were made in pristine Florida springs in the presence of dozens (even hundreds) of manatees. You will appreciate the amazing soundscape of Florida springs and the protected freshwater manatee habitats free of anthropogenic noise (and also free of snapping shrimp that dominate salt water manatee habitats). There are also some amazing manatee calls there, so make sure to try out this new, exciting workflow.

Project Significance

Manatee acoustic communication has not been studied extensively, and we still do not know the potential function(s) of manatee calls beyond mother and calf contact. Additionally, categorizing calls and later relating them to behavioral states and events could help make a better sense of the data recorded in the future via passive acoustic recorders. Finally, understanding the categories of manatee calls and individual variations could help create a system for tracking manatees via passive acoustic recordings and potentially warn boaters about a manatee presence in the area.

Note: The white scars on this juvenile manatee's back are from a boat propeller.

References:

Mann, D. A., O'Shea, T. J., and Nowacek, D. P. (2006). Nonlinear Dynamics in Manatee Vocalizations. Marine Mammal Science, 22(3), 548-555.

O'shea, T. J., and Poché Jr, L. B. (2006). Aspects of Underwater Sound Communication in Florida Manatees (Trichechus manatus latirostris). Journal of Mammalogy, 87(6), 1061-1071.

Reep, R. L., & Bonde, R. K. (2006). The Florida manatee: biology and conservation. University Press of Florida.

Umeed, R., Attademo, N., Löffler, F., and Bezerra, B. (2017). The Influence of Age and Sex on the Vocal Repertoire of the Antillean Manatee (Trichechus manatus manatus) and Their Responses to Call Playback. Marine Mammal Science. DOI: 10.1111/mms.12467