Research

Current Project: Manatee Vocalizations

Our research is focused on the sounds manatees use and how they use them when interacting with other animals.

Understanding the sounds manatees create could potentially be used for:

  1. Determining presence/numbers of animals where habitat is very large or access to it is limited
  2. Areas where there is a lot of vocal  activity or chewing sounds could be important habitat for Sirenian species

Here is just a brief glimpse into our work:

Did you know manatees use sound to communicate?

Manatees vocalize frequently when playing, travelling, and when they are in large groups.  Manatees also vocalize when they are resting or feeding but not as often. Vocalizing may be most important to moms and their babies. Calves are dependent upon their mothers for 1 ½-2 years.  Mothers and their calves call to one another when they are separated, while travelling, and during approach by another manatee.

Manatees consume a lot of vegetation which can produce these loud chewing sounds. Listen below to hear manatee chewing sounds.

 

Listen below to a recording of vocalizations from a group of manatees.

Manatee vocalizations are produced from bilateral folds in the throat area, somewhat similar to vocal folds known as the voice box  in humans. Manatees make multiple types of sounds that look different from one another. Part of Beth’s research is determining the  manatee “vocabulary”. Featured below are some of the variety of sounds recorded from wild manatees.

This image is called a spectrogram with frequency on the vertical axis and time on the horizontal axis.

 

If you want to learn more, consider donating to Sirenian International to receive updates on our research and have an opportunity to speak with Beth about her work!

Bone mechanics

Did you know that bone is dynamic and can change all the time based on the stage of an animal’s growth, health, diet, and movement in its day to day life? Bone is a very metabolically active tissue (much more so than cartilage, for example) and therefore can serve as an anatomical signal for the animal and its environment! Danielle’s  research focuses on how manatee bone is structured throughout growth and in different parts of their spine, and what this means about how their spine supports swimming and lifestyle as large, plant-eating aquatic mammals.

Instron E1000
Instron E1000

One question that she has in her research is how strong manatee bone is and how this strength is different as they grow from a newborn to an adult. Strength is defined as a material’s ability to resist failure, and it can tell us a lot about how a material responds to forces applied to it. Strength can be calculated through a process called material testing. To the right is a picture of an Instron E1000, which test samples in compression (push) and tension (pull).

To test how strong manatee bone is,  she dissects vertebrae (bones from the manatee spine) and prepares them for mechanical testing. **All bones are collected from dissections of manatees that have died from watercraft collision, red tide, natural, or unknown causes. Agencies that responded to deceased manatees include Florida Fish and Wildlife as well as various stranding networks throughout Florida.** Bone pieces are then loaded into the material tester where the top plate applies a force on the sample. Strength is calculated based on the force it takes to permanently deform the material, which we quantify in megapascals.

The graph below shows how strong manatee vertebrae soon after birth, when they are calves (<1-2 years old) and as adults (physically mature; >6 years).  Danielle found that between the newborn and calf stage, which is only separated by a year or two, bone strength from vertebrae more than doubled, while the increase in strength between calves and adults was only about 30%. What does this tell us? This most likely indicates that bone in the spine of these aquatic mammals develops very quickly to support their swimming. Manatees are what we call precocial animals, or ones that can move around really soon after birth! All aquatic mammals are precocial in their swimming because they must surface to breath air regularly.

Stay tuned for updates!
If you want to learn more, consider donating to Sirenian International to receive updates on our research and have an opportunity to speak with Danielle about her work!


Book us for a Talk or Presentation

One of our scientists is more than happy to come to your area (within Florida, however exceptions can be made) and talk about our research or about Sirenians in general.