Manatee Migration Update: April 14, 1999

Today's Report Includes:

Take A Deep Breath!

"Much has happened since I sent my last data, and I'll take a deep breath and fill you in! I mentioned last time that Xoshi was on the move. All throughout the March 27-28 weekend, we watched (rather helplessly) as her poor quality locations fixed farther away from the mainland. By late Sunday (3/28), we realized something had to be done....", reported Cathy Beck.

Challenge Question #15:
"Plot Xoshi's data on your map, study the map legends, and see if you can determine why the scientists were so concerned."

Challenge Question #16:
"Which day did Xoshi travel the farthest? How far did she travel that day?

Here are Xoshi's data:
 Date Latitude (N Longitude (W) 03/25/99 25.619N 80.166W 03/27/99 25.615N 80.128W 03/28/99 26.910N 79.807W 03/28/99 27.160N 79.914W 03/29/99 27.567N 79.878W 03/29/99 28.133N 79.966W 03/29/99 28.704N 80.063W 03/29/99 28.753N 80.107W 03/30/99 28.681N 80.241W 03/30/99 28.410N 80.614W

For help in using satellite data to calculate distance, see:

In The Good Old Summertime
Cathy also reported "It is really getting quite warm here now and our manatees are beginning to explore their summer habitats." Take a look at today's data at the end of this report. Can you see which manatees are starting to explore?

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

Learning By Example: Discussion of CQ #13
Did you figure out why Cathy thought it was such good news that Brian has been following other manatees? Brian was rescued two times previously for malnutrition and emaciation. Knowing that Brian is following other manatees is good news because Cathy is "hoping that he learns good feeding sites from the others." Bon Appetit, Brian!

A Record-Breaking Season For Ranger Wayne

 Ranger Wayne Hartley
"I think the season at Blue Spring has ended. The season began on December 15 and ended on March 18, which was a month late beginning but a fairly normal end."

"We had a record number of manatees seen during the season at 114, last year's was 106. A record ninety-nine spent the whole winter with us, up from ninety-two last season. We had a record ten calves for the season, up from eight several previous years. The highest single count was eighty-six, one short of the record set last year."

Ranger Wayne also sent the latest data. Can you see how these data confirm the season's end at Blue Spring?

 Date Air Temp High(C) Air Temp Low(C) River Temp (C) Run Temp. (C) # of Manatees 03/28/99 27 5 22 22.5 0 03/29/99 29 9 22 nt 0 03/30/99 32.5 12 22.5 22.5 0

The Lone Ranger: Discussion of CQ #14
In last week's Challenge Question #14, we asked "Why did so many manatees come into the run on 3/17, while so few came in on 3/24?"

As you learned earlier, the manatees swim into the warm run to escape colder river water. On 3/17, the river temperature dropped to 18.8, almost 4 degrees cooler than the run, and 48 manatees came in. But on 3/24, the river temperature was 21.5, only 1 degree less than the run, and no manatees came in. Also, while the air temperature on both days was low, this did not affect the river temperature on 3/24, which stayed high enough that the manatees remained in the river.

The More Surveys The Better: Discussion of CQ #11 & 12
 Dr. Bruce Ackerman
After reporting the THIRD aerial manatee survey, we asked in CQ #11 "Why was Dr. Ackerman so excited to conduct a third survey?"

Dr. Ackerman gave us several reasons why having three surveys is better: "The weather conditions have a lot to do with how accurate the manatee aerial survey counts are. Sometimes the weather is warm or cold, sunny or cloudy, calm or windy. Sometimes it has been warm or cold for the several weeks before the survey. Sometimes the weather is great in one part of the state, but at the same time, not so good in another part of the state. The result is, we don't always know how accurate the survey actually is."

"We don't know how large the population really is, so we really don't have a way to gauge the accuracy of the surveys. But we do know that the size of the population usually doesn't change very fast. Doing 3 surveys each winter gives us a better chance to compare the results between the surveys, and to see how variable the surveys can be in the space of just a few weeks. If we relied on just one survey in a year, sometimes it could be very low and sometimes very high."

"Doing 3 surveys also gives a better chance to hit the perfect weather conditions. Usually we consider the highest count to be the most accurate and reliable indication that we have of what the size of the manatee population really is. (If you were trying to hit a hard target, like the basketball hoop from mid-court, the more times you shoot, then the more likely you'd be to get close and eventually get one in, right?)"

We also asked CQ #12 about "What do you think the latest survey data signify to the manatee scientists? Which data are positive? Which data are negative? Explain why."

Recent comments by Dr. James Powell, manatee research administrator for DEPís FMRI, explain how the third survey data may be both positive and negative:"Though the third statewide count this year was relatively high, we are concerned about the low counts on the east coast of Florida. The total statewide number may be misleading since manatees in some regions may be doing well and experiencing an increase in population while manatee populations in other areas may have higher mortality that reduces their numbers."

This is another reminder to be careful when interpreting numbers. They are very exact--but sometimes their meaning may not be so clear.

How to Respond to Today's Challenge Questions: