Manatee Manatee
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Manatee Migration Update: March 7, 2001

Today's Report Includes:

Field Notes From Cathy Beck

"Hello Again Students!
Jim Reid and Dean Easton have each been very busy tracking the manatees, and we're glad to report they all seem to be doing fine. Their latest tracking data is provided below, and here's some 'first hand' information on what they've been up to.

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

Dean's Daring Duty
"Grace has been making consistent movements back and forth between Port of the Islands (POI), her release area, and some sea grass beds near small, unnamed mangrove islands. We are interested in what is triggering her moves--time of day? Tide cycle? To study Grace's movements in more detail,we wanted to attach a Global Positioning System (GPS) tag to Grace's existing tag assembly while she is swimming freely in the water. This may sound easy, but it's actually quite an accomplishment!

"We gave Dean the assignment to attach the GPS tag to Grace--without recapturing her!

Challenge Question #14:
'If you had Dean's duty to attach the GPS tag to Grace, how would you get close enough to her? How might Grace react? Are there any dangers you should be aware of?'

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

"The GPS tag will capture Grace's locations every 15 minutes. When we remove the tag from her in about two weeks and download the data onto our computer, we can determine her movements on a fine scale.

Side By Side
"Addison and Nina both moved separately to the north, but we recently heard that they we're sighted together again, at least for a while on March 1. We received a public sighting report from a woman who lives on a residential canal in Marco Island. She spotted both Nina's and Addison's tags, side by side, just off her seawall!

Challenge Question #15:
'If the scientists hadn't received a public sighting of Addison and Nina on March 1, what would they have been able to determine from the data alone about their locations that day? Can you tell on which dates they were closest to each other?'

Addison

Nina

03/02/01 25.977N, -81.702W 03/02/01 25.979N, -81.713W
02/28/01 25.956N, -81.706W 03/01/01 25.979N, -81.702W
02/26/01 25.977N, -81.702W 02/26/01 25.983N, -81.718W


Note: Remember you can use the following Web source to help calculate distance:

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

"Megan and Santina have both basically remained in the vicinity of their original release area, Port of the Islands (POI).

Surfer's Side Trips: Discussion of CQ #13
"Since the last report, Surfer has spent much of her time near the mouth of the Lostman's River, but she also found time for another side trip up the Broad River on 2/23.

"In Challenge Question #13, we asked 'Why do you think Surfer would swim up a river? Are there any daily conditions that you can think of that might affect when she would leave the ocean and head up river?'

"There are many reasons WHY Surfer might swim up from the ocean up into a river. These include getting access to freshwater or access to freshwater vegetation, and seeking warmer water temperatures.

"As for WHEN Surfer would swim upriver, one factor we are studying is the possible effect of tides. Swimming upriver generally would be easiest with the incoming or 'high' tides, when the water would be deeper. During low tidal stages, upriver access at some river entrances is not possible because it is simply too shallow.

"The idea to study the influence of tides began when Susan and Dean were observing Surfer in the field several months ago. She appeared to show a pattern of every couple of days traveling up the rivers into the backwaters with incoming or high tides. Susan began to look at the tide tables and compare that to Surfer's PTT satellite locations we received here - and tide stage did appear to influence Surfer's movements in and out of the rivers.

"At this point, we cannot make any definite conclusions about the influence of tides on manatees generally. What we've seen so far with Surfer are our observations only, based on a sample size of one. We hope to get a bit more insight with more tagged manatees."

Cathy Beck
Sirenia Project
Gainesville, FL

Abiding the Tides
Changing Tides
Photo Courtesy NOAA

If you've ever been to the seashore, you've probably seen how the water level rises to a "high" tide and similarly falls to a "low" tide, usually twice each day. Tide tables predict the local height of the water surface, indicating the times each day when the water is highest and when the water is lowest.

As Cathy Beck mentioned, water levels at some rivers entrances are very shallow during low tides.

Using the Tide Table below, what information might a manatee need to know about tides so she doesn't risk getting stuck in the river in water that's too shallow?

Challenge Question #16:
a) "The highest tide for this day is _____feet.
b) The lowest tide for the day is _____feet.
c) Between the lowest and the highest tides, the water level rose _____feet.
d) Between 16:54 and 22:29 the river level increased ______feet/inches per hour?
e) According to the Tide Table, I think the best time for a manatee to leave the river to avoid the risk of getting stuck in the river would be _____."

Tide Table

Date Time Height of Water
2001-03-06 5:44 EST -0.90 feet
2001-03-06 11:23 EST 2.04 feet
2001-03-06 16:54 EST 0.73 feet
2001-03-06 22:29 EST 4.14 feet

Challenge Question #17:
"In addition to tides, there are many other things that can affect water level or depth on or near a seashore. What conditions can you list that may affect the water level? (Hint: Try to think of things above and below the water.)

(To respond to these questions, please follow the instructions below.)

Do Manatees Still Need Protection?
In the last Update, Dr. Ackerman reported that this year's aerial manatee survey counted a record 3,276 manatees compared to the previous record of 2, 639 manatees in 1996.

What does this year's record high manatee count really mean for the manatee population? Are there actually more manatees than in previous years? Are manatee protection regulations still needed?

Dr. Ackerman indicated that even with the high count, scientists remain cautious about the overall manatee population.
"Counts can be highly variable due to weather conditions, and this year's count isn't entirely unexpected", he said, referring to the perfect counting weather this year.

A Whole Species' Life Savings
He also emphasized that the manatee is an endangered species, and that the record count doesn't change the need to protect manatees.

"Even 3,000 is not that many individuals of an endangered species. It might seem like a lot more than 2,600, but it's not that much more. It's like having your life savings being $3,000."

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.

Airborne Ackerman Answers CQ: #8, #9 & #10
Air and Water Temp Graph

In Challenge Question #8 we asked why the following conditions were the perfect prescription for manatee surveys:
  1. A prolonged cold front,
  2. A significant drop in water temperature, and
  3. A sunny and windless day following the cold front

Manatees are extremely cold sensitive, and Dr. Ackerman explains that "the colder water temperatures cause the manatees to seek out warm water sites, and the warmer air of the sunny day encourages them to float. These conditions encourage the manatees to float at the surface, which makes it easier to see and count them."

In Challenge Question #9 we asked "Why might the prolonged cold spell that contributed to the high manatee count also have a negative impact on the manatee population?" According to Dr. Ackerman, "in the past, similar conditions have resulted in higher than normal manatee mortality due to cold stress. For that reason, we had FWC biologists on alert to respond to any manatees that are affected."

In Challenge Question #10, we asked if you were a manatee scientist, which of the sea surface temperature map days would you choose to conduct your manatee count? The deeper blue water temperatures on Map B indicate that it would be the best day for a manatee count, because it showed the coolest water temperatures. No surprise that Map B was actually a map of conditions on the days of the count.

To illustrate the perfect manatee counting weather conditions for this year's count, Dr. Ackerman prepared a graph of air and water temperatures at Sarasota Florida from October through February. Look at the conditions on the graph above before the January 5-6 synoptic survey. Can you see the prolonged cold front and drop in water temperatures that are part of the prescription for a successful count?

Ranger Wayne's High Voltage Manatees

Ranger Wayne Hartley

Joules goes free
Photo Courtesy Wayne Hartley

"On 22 February, Sea World released two small males that had been saved from a power plant outflow in Jacksonville. The power plant was about to shut down and wouldn't have got them through anyway. "Amp" was branded 98, and "Electrode" was branded 97. On 1 March, they also released the little girl, "Joules" branded 95. One more little male to go."

Ranger's Roll Call
Here is the latest data from Ranger Wayne, who says he expects it to be "Cold this week." What changes would you expect this to bring in the number of manatees in the run?

Date

Air Temp Low(C)

Air
Temp
High(C)

River Temp (C)

Run Temp. (C)

# of Manatees

02/14 16 29 21 nt 0
02/16 17 30 22 22.5 0
02/19 8 26 21 nt 3
02/26 11 33 22 23.1 0
03/02 17.5 32 23.2 22.5 0

Ranger Wayne Hartley
Blue Spring State Park

Canoe Count: Discussion of CQ #11
In this Challenge Question we asked "Can you see a pattern or trend in Ranger Wayne's data that might explain the changing number of Manatees counted in the run at Blue Spring each day?"

Ranger Wayne reports that the chief factor to explain the number of manatees in the run is water temperature. The colder the water in the St. Johns River, the more animals in the run. This pattern is shown in the data. For example, if you look at the days when the most manatees were counted, January 2 and December 23, you will see that these were also the days when the water temperature in the St. John's River was at its coldest.

Remember, the other factor is timing. Their movements in response to temperature are not always immediate.

Sea Cow Conversions: Asking CQ #12 Again
We're sending it out again to test your ability to convert centimeters into inches, and pounds into kilograms:

Challenge Question #12:
"What are the new manatees' lengths in inches, and what are their weights in kilograms?"

Name

Length(cm)

Inches

Weight(lbs.)

Kilograms

Megan 319 cm   1,085 lbs.  
Addison 248 cm   680 lbs.  
Nina 270 cm   885 lbs.  
Santina 285 cm   990 lbs.  
Grace 286 cm   970 lbs.  


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

Ahoy Addison: Discussion of CQ #4
Thanks to everyone who answered Challenge Question #4, which asked: "How did the crew know it was Addison who swam in the net?"

5th grader Simone from Ms. Quinn's class in Tampa, FL really "netted" the answer: "The manatee must have had markings from motor boats."

Cathy Beck explained that since the 1970's the Sirenia Project lab has developed a photo-identification catalogue of individual manatees recognizable by distinct and permanent features - almost all of which are scars and mutilations caused by encounters with boats. Cathy manages that database, which has grown to include nearly 1,500 manatees. This database includes much valuable information from Ranger Wayne Hartley, who sends us information on all the Blue Spring manatees that he knows so well!

What's in a Name?: Discussion of CQ #5
We also had some great answers to this question, which asked "How do you think manatee names are chosen?"

* Ms. Gunning's Grade 9 class from Quitman, MS thought "they may be named after the first person who found them." Quitman High School

* Carson from Ms. Quinn's class in Tampa, FL said "I think manatee names are chosen by the person who first spots them." And classmate Anastasia from Ms. Quinn's class said "manatee names might be chosen by where they are found."

Cathy Beck reported that "many of the manatees are assigned names that describe the particular shape or pattern of scars (e.g. Arrow, Crescent, Duck, and Trident). The manatees that are released from captivity were almost always named by the oceanaria staff. The oceanaria usually assign names based on the rescue location (e.g. Naples) or to honor someone. We assign names to our tagged manatees based on the markings it has, the place of capture, or as a thanks to someone who has been especially supportive or helpful as a volunteer, etc. Our primary criterion is that we try to not repeat a name once it is assigned!

"Of the six manatees you are tracking this year, Jim Reid wrote that 'Santina was named after the name of a nearby bay. Nina was named for a dedicated Fish and Wildlife Service volunteer that helped on the capture. All others were named for friends and relations of members of the capture crew.'"

Discussion of CQ# 6 & #7
In Challenge Question #6 we asked "Why do you think the cold-stressed manatees were emaciated?", and two students did a nice job answering this:

* Ms. Gunning's Grade 9 class from Quitman, MS answered that "When the temperatures drop, the manatee will stop eating." Quitman High School

* And 5th Grader Patrick from Ms. Quinn's class in Tampa, FL told us that "I think that when the manatees get too cold they don't eat enough and then the fat on them shrinks"

According to Cathy Beck, cold stressed manatees become emaciated because "when it is very cold, manatees will often remain in warmer water and fast, rather then expend energy to travel to foraging habitat."

For Challenge Question #7, we asked "What is in the Everglades that makes the scientists a little more concerned this year about the manatees losing their transmitters?" Cathy Beck explained in the Everglades there are "just lots of alligators around", which occasionally are known to bite off "transmitter tidbits"

How to Respond to Today's Challenge Questions

IMPORTANT: Answer only ONE question in each e-mail message.

1. Address an E-mail message to: jn-challenge-manatee@learner.org
2. IMPORTANT: In the Subject Line of your message write: Challenge Question #12 (OR #14, OR #15, OR #16 OR #17)
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 21, 2001

Copyright 2001 Journey North. All Rights Reserved. Please send all questions, comments, and suggestions to our feedback form

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