Manatee Migration Update: February 19, 1997

Calling All Manatees!
In our last update, scientists were scrambling to survey manatees during a cold front. Since nobody knows how many manatees there actually are, the goal of these winter surveys is to try to count them. When working with an endangered species, numbers are very important. Scientists need to know the size of a population in order to answer to these critical questions:

• How endangered are these animals?
• Are their number rising or falling? How quickly?
• And ultimately, are we making progress in protecting them?

Imagine the challenge of counting manatees! They live underwater--often cloudy, murky water. They don't have set daily routines--they feed, rest, and move throughout the day and night. When they surface for air it's only for seconds, and the time between breaths can vary from 5-12 minutes. While they sometimes rest on the water's surface, other times they rest on the bottom! They often gather in groups, coming and going from the surface like big bubbles in a pot of boiling water.

Biologists study animal behavior carefully, and use this knowledge in clever ways. Last week we asked you to consider this question:

Challenge Question #1
"Why do you think the scientists mobilized quickly to conduct the aerial survey when the cold front arrived?"

Thanks to the many students who responded to this question. (Click here to read their complete answers.) Most everyone seemed to know that manatees don't like cold water, just as these students did:

From Florida:
"The manatees would change positions quickly trying to find warmer waters". OHS Science Lab (ohssci@gnv.fdt.net)

From: COLORADO
"We think the scientists mobilize quickly to see how the manatees respond to a cold front, or because the manatees might go to warmer temperatures when the cold front comes."
Susan Hoffman (shoffman@tomichi.ghs.gunnison.k12.co.us)

So where do the manatees go when it's cold? As it happens, when cold weather arrives manatees come together at special sites known as "warm water aggregations". Cleverly, the scientists know where these places are and they go there too! During the surveys, 19 teams of experienced researchers covered all known manatee winter aggregation sites in Florida and Georgia. Not surprisingly, these winter refuges include such places as Ranger Wayne Hartley's hot springs (see below). Other favorite hotspots are the warm water outflows of 5 power plants along the Florida coast. The scientists watch the weather maps closely, and plan the surveys when it's as cold as possible. Here's Dr. Ackerman again, this time making plans for a February survey:

"Weather will be cool Tuesday morning 2/11 and Wednesday morning 2/12. Hopefully it will reach the low 40's in Tampa. Due to the short window, most teams will fly on Thursday 2/13, on both coasts. This will give the manatees more time to arrive at warm water, from being widely dispersed in the recent warm spell."

Missing a Few Manatees?
You may be surprised by the results from this winter's 2 surveys. They are discussed in these news releases from Dr. Ackerman (JANUARY NEWS RELEASE , FEBRUARY NEWS RELEASE ) and a chart summarizing all surveys conducted since 1991 is provided below. Using this chart and the press releases, see if you can answer this Challenge Question:

Challenge Question # 2
"How many more manatees were counted in January, 1997 than were counted in February, 1997? What percent change is this? What reasons does Dr. Ackerman give for this difference?"

DATE OF SURVEY       TOTAL
Jan. 23-24, 1991     1,268
Feb. 17-18, 1991     1,465
Jan. 17-18, 1992     1,856
Jan. 21-22, 1995     1,443
Feb.  6-7,  1995     1,822
Jan.  9-10, 1996     2,274
Feb. 18-19, 1996     2,639
Jan. 19-20, 1997     2,229
Feb. 12-14, 1997     1,709

Satellite Data from Sirenia Project

TODAY'S SATELLITE DATA

Special thanks to Drs. Jim Reid and Cathy Beck of the USGS-Biological Resources Division's Sirenia Project for providing satellite tracking data again today! How did our five favorite satellite-tracked manatees respond to recent temperature changes? Now that you know how important temperatures are to manatees, why do you think the five manatees might be located where they are? What do you think they are doing in these places? Here are Cathy Beck's comments:

"The cold front that was expected did come, but was rather mild and short- lived. It dipped into the 30's on Friday and Saturday nights (Feb. 14 & 15), but has been in the 70's in the days. The front never extended into the south and has had no noticeable affect on the manatee's movements. Even Mercury, who is in Georgia, moved only slightly and still this morning is in a feeding area, probably only yards from Friday's location. Since this cold front fizzled out we have canceled the scheduled recapture attempt for Marmontel on Thursday. We had planned to catch her as she entered the warm water. The current plan is to try again on 5 March. I'll keep you posted!"

Manatee Roll Call at Blue Springs
Can you see a trend in the number of manatees counted by Ranger Wayne Hartley at Blue Spring State Park, based on temperatures? Once again this week, he's provided a snapshot of life at one of the favorite manatee hotspots. Here's his report.

As we mentioned in last week's report, manatees are not lightweights! They can weigh between 800 to 1,200 pounds. Some might say they are as big as a whale! We know that that is an exaggeration, but thinking about whales raises a good Challenge Question.

Challenge Question # 3
"Why do you think a large marine mammal like the manatee cannot tolerate cold water when another large marine mammal--the whale-- can?"

How to Respond to Today's Challenge Questions:
Please DO NOT answer both questions in one message!

How to Respond to Journey North Manatee Challenge Question # 2

1. Address an e-mail message to: jn-challenge-manatee@learner.org
2. In the Subject Line of your message write: Challenge Question #2
3. In the body of the message, give your answer to this question:

Challenge Question # 2
"How many more manatees were counted in January, 1997 than were counted in February, 1997? What percent change is this? What reasons does Dr. Ackerman give for this difference?"

How to Respond to Journey North Manatee Challenge Question # 3

1. Address an e-mail message to: jn-challenge-manatee@learner.org
2. In the Subject Line of your message write: Challenge Question #3
3. In the body of the message, give your answer to this question:

Challenge Question # 3:
"Why do you think a large marine mammal like the manatee cannot tolerate cold water when another large marine mammal--the whale-- can?"

Don't Forget!
Please tell us who you are! Include the name of your school, and your state or province.

The Next Manatee Migration Update Will be Posted on March 5, 1997.