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Manatee Migration Update: March 17, 1999

Today's Report Includes:

Where's Ivan? Dicussion of CQ #6
Manatee Migration Map

Cathy Beck tells us that Ivan is doing just fine, and he's still being seen with his mom, Dmitra. So why haven't we received any satellite data from Ivan for so long? Cathy's got the answer:

"Jim Reid and Susan Butler finally caught up with Dmitra and Ivan's transmitters on Wed. 2/17 in New Port Richey! Both tags had been hit by a boat! Ivan's transmitter was completely sheared off, leaving only the nose cone attached to the end of the tether. Dmitra's tag was also struck. Jim said that when he saw Ivan's tag he had to hesitate before looking down. Thankfully, neither manatee was injured! Jim was able to get the remains of the old tags off both animals and attach a new transmitter to Dmitra's belt; but they swam off together before he could retag Ivan. We hope to retag Ivan soon!"

There's still no data from Ivan, but you'll notice data for three new manatees including "Brian" (a male who many of you may remember from last year), "Xoshi" (a female), and "Crystal", a female calf who's still with her mother. Like Ivan, Crystal may also separate from her mom this spring, so keep watching for more of Cathy's "calf" news.

Today's Satellite Migration Data
(Courtesy of U.S. Geological Survey's Sirenia Project)

My, What A Lovely "Transmitter" You Have!

Manatee with transmitter

Have you ever wondered HOW these transmitters are used? What do they look like, how do the scientists attach them to the manatees, what kind of radio signals are sent out, how long do the transmitters last, and what happens if the transmitter gets caught in something? Well, read on for some insights about the transmitters.

Floating Radios

Illustration of a Manatee transmitter

The radio transmitters are contained inside of floating plastic cylinders about 39 cm long and 9 cm in diameter. The cylinders have a 20 cm wire antenna on the top of them, and every cylinder is color-coded with large identifying letters and engravings on them. Each cylinder actually has two different transmitters inside it, one called a VHF transmitter which sends specific radio frequency signals to scientists in the field using a portable receiver, and another called a Platform Transmitter Terminal or "PTT" that sends out location signals to an orbiting satellite. Typically, the PTT will send from two to six different location points for each tagged manatee every day. Besides "location" information, data is also sent on manatee "activity" (# of dives, duration of dive, # of times the transmitter tips greater than 90 degrees, i.e. swimming, playing, etc) and temperature.

According to Cathy Beck, satellite tracking data can be inaccurate or be interrupted for several different reasons. "The quality of the location plotted by the satellite varies, depending on whether the manatee (actually the antenna) is at the surface when the satellite passes--the antenna must reach the surface in order to broadcast the signal to the satellite. Also, data quality can be affected when there are a lot of structures or vegetation that may interfere with the signal."

Backpacks, Peduncle Belts, Tethers and Alligators?!


Journey North students tracking the migration of the Bald Eagle know that the eagle wears a "backpack" transmitter. Manatee transmitters, on the other hand, are attached with a "peduncle belt" and a "nylon tether." The belt goes around the manatee just in front of its tail, in an area called its "peduncle", and the tether is a stiff nylon rod (about 10 mm in diameter and 130 to 200 cm long) that connects the belt to the transmitter. Each tether has a "weak link" built into it, which will break and allow the manatee to swim free if the tether or transmitter ever become snagged on something such as a dock, a boat, thick vegetation, or even a hungry alligator!! Yes, that's right, scientists have reported seeing an alligator pull a transmitter off a manatee, and also have found alligator teeth marks on other transmitters!

Solving the "Mo" Mystery: Discussion of CQ #7

Photo: U. S. Geological Survey, BRD, Sirenia Project

Mo must not have read the manatee rule book, because his journey broke all the rules! Mo was released in shallow waters with warm May weather, so there seemed to be no reason for him to move. But within 30 days, Mo had traveled 284 miles south and moved some 57 to 75 miles out to sea!

Mo's long distance journey came as somewhat of a surprise. "He was released at Crystal River and stayed there for about 2 weeks, with lots of 'location' data. Then for the next 3-4 weeks we only got 1-2 locations as he traveled south. He then popped up in the Dry Tortugas with some good locations, where Jim was able to catch up with him. Actually that simplifies the story. Besides 'location' information we receive data on 'activity'. This information indicated it was attached to the manatee, rather than rolling around in a boat (perhaps picked up by a fisherman)", said Cathy Beck. When the location data were finally received again, Mo was well outside normal manatee habitat. In fact, Mo is the first tagged manatee ever documented to move so far offshore!

Jim Reid

Why did Mo travel where he did? Thanks to the many student detectives who tried to solve this unique manatee mystery. According to biologist Jim Reid, "We believe that Mo wandered offshore into deep waters where he drifted south with the currents".

Mo was far from food and fresh water, and Jim traveled to the Dry Tortugas islands to lead the rescue effort. With invaluable help from the National Park Service Dry Tortugas staff and a Sea World Orlando field crew, Mo was found drifting about 20 miles west of the Dry Tortugas in waters that were 175 deep. He had lost 180 pounds from his release weight of 735 pounds, and was dehydrated and malnourished. Mo approached the Sea World rescue boat, and was captured with a hoop net. Thankfully, he is back at Sea World, and is expected to make a full recovery--whew!

Challenge Question #9:
"From what you've learned in today's report about transmitters, why do you think Mo's 'location' data were interrupted for 3-4 weeks?

(To respond to this question, please follow the instructions below.)

By Land, Air and Sea! Discussion of CQ #8

Dr. Bruce Ackerman

As many of you saw, the number of manatees counted in January and February 1999 (1,873 and 2,034 manatees) were lower than the counts in January and February 1996 and January 1997 (2,274, 2,639, and 2,229 manatees respectively). But the February 1999 count was higher than the count from January 1998 (2,022).

Just what do the lower manatee counts mean? Are there actually fewer manatees than in 1996 and 1997, or do other factors affect the counts? Mrs. Sgalippi's 4th grade manatee group in Horsham, PA suggested one factor that could affect the count:

"We think that it is because in the past years it has been colder than this year so less Manatees are coming" (

According to Dr. Ackerman, "biologists are confident that the lower count does not signal a sudden decrease in the size of the population, which we still estimate to be at least 2,400." Instead, the lower counts were the result of warmer weather this year. "Because this has been an unusually warm winter, it has been difficult to find the kind of colder weather that results in the highest counts."

Researchers normally want a prolonged cold front followed by a clear, windless day to conduct the best count. The colder water temperatures cause the manatees to seek out warm water sites, and the clear day encourages them to float, making them easier to count. Before the first count this year, there had been a long warm spell and "manatees were still migrating to their wintering sites", Dr. Ackerman said. By the second count, "a series of cold fronts in mid-February dropped the water temperatures enough to attract many manatees into their warm water aggregation sites."

As you can see, the number of manatees from one count to the next can be the result of many things, and a count can vary by several hundred manatees simply due to weather conditions. Be careful with numbers. They are very exact--but sometimes their meaning may not be so clear.

Dr. Ackerman hopes to do another aerial survey to help refine the estimate of the minimum size of the population, so stay tuned for more "in-flight" information.

Life's A Challenge!
The manatee population counts remind us of how difficult it is for a manatee to survive. Think about the many causes of disease and death that manatees face in the wild, and then try to answer the Challenge Question below. Before answering, you may want to review this Web site:

Challenge Question # 10
"What are all the risks that cause disease or death to manatees. Which one's are "natural causes", and which ones are human-related?"

(To respond to this question, please follow the instructions below.)

Ranger Wayne's Roll Call

Ranger Wayne Hartley

Here's the latest data from Blue Spring--do you still see the correlations between temperature and number of manatees in the run? With the warmer weather of Spring on it's way,keep watching for changes at Blue Spring!


Air Temp High(C)


River Temp (C)

Run Temp. (C)

# of Manatees





































How to Respond to Today's Challenge Questions:

Please answer ONLY ONE question in each e-mail message!:

1. Address an E-mail message to:
2. IMPORTANT: In the Subject Line of your message write: Challenge Question # 9 (OR # 10)
3. In the body of the EACH message, give your answer to ONE of the questions above.

The Next Manatee Migration Update will Be Posted on March 31, 1999.

Copyright 1999 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form

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