Manatee Migration Update: April 9, 1997

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Time For A Check-Up
Since our last report, we have received some great news about Dakota, who you might remember was an orphan manatee that had been rescued, rehabilitated and then released. Periodically, scientists recapture manatees like Dakota to give them a "check up" and be sure they are succeeding in the wild.

On March 22, Cathy Beck wrote and told us about plans to recapture Dakota. "Dakota is moving south along the coast. We do not know if he is with other animals or what prompted his move. On Monday, four from our lab and Sea World staff and a vet will capture him for assessment and to change his tag before the battery in the transmitter dies. You remember that he was a captive-rehab release. These manatees are captured periodically to check their health, primarily the thickness of subcutaneous fat layers using an ultrasonic device. We want to be sure they are succeeding as wild manatees! All indications are that Dakota is doing fine. However,there is always the possibility that he will be taken back to Sea World if he is emaciated or has sustained any serious injuries."

On March 31, Cathy Beck wrote again with the good news about Dakota's recapture and check up: "Dakota was captured last Monday, but we did not hear from the field people until they returned on Wednesday. He is doing well, and was with two other manatees. He was released immediately."

Cathy also let us know that "Mercury and March are still up in Georgia. March is using the Amelia River (good cordgrass)."

We have also received the latest satellite tracking data from Cathy Beck, but before we get to that, lets look at the answers to Challenge Question #7, where we asked "As of March 13th, how many miles is north is "March" from her location on January 6th (28.498 N, 80.736 W)?"

An easy way to estimate the distance between two locations on map is to use the scale of the map, which tells you that 1 inch of distance on the map is equal to a certain number of miles in real distance. Use a ruler to measure the distance in inches between the points, and then convert the distance from inches to miles using the map's scale. Students from New Jersey and Minnesota gave us these estimates:

From: NEW JERSEY
We think as of 3-13-97, "March" is about 180 miles north from her last location on 1-6-97.
-Jackie, Brittany & Caitlin
Tracey Schaum (oradell@intac.com)

From: MINNESOTA
We are doing Journey North in small teams in our classrooms. Our group answered the challenge question #7. This is the answer we got: 187.5 miles. Our names our Chris, Courtney, Danny, and Megan. We are from Centerpoint Elemantry in MN.
Thank You,
Chris, Courtney, Danny, and Megan
MahoneyMug@aol.com

More About The Threats To Manatees
In our last report, Nancy Sadusky and Ann Spellman described some of the threats that manatees face every day such as watercraft, crab pots and microfilament fishing lines. Because manatees are endangered, it is extremely important to understand the threats to their survival. In addition to the man-made threats that Nancy and Ann described in the last update, there has also been a natural threat to the manatees' health.

A Natural Threat?
In 1996, a single catastrophic event occurred and was responsible for 151 manatee deaths, mainly adults. For a time, scientists did not know what was killing so many manatees in such a short time period. With so few manatees left in the United States, many people were very concerned about what was causing these deaths. Manatee necropsy reports showed that the these manatee deaths were attributed to red tide, a term used for the proliferation or "blooms" of tiny marine organisms called dinoflagellates. The organism's pigments can cause the water to appear red, green, or yellow. Microscopic, but found in great abundance, they give off a toxic byproduct that affects the central nervous system of creatures in the area of the bloom. The red tide epizootic began on March 5 and continued through April 28 along Florida's southwest coast, wiping out approximately 15% of the known west coast population of manatees.

In 1982, another outbreak of red tide was believed to have contributed to the death of 37 manatees. Over the years however, red tide manatee mortality events have been rare. Red tide is currently considered to be a natural event and, therefore, may not be preventable. But scientists are currently looking at possibilities to reduce the risk to manatees during red tides. Monitoring and prediction of red tide distribution has been deemed crucial. The possibility of reducing water salinity in certain areas is also being investigated as red tide requires high salinity water to survive and does not do well in water less than 2.5% salt like brackish or river water.

Challenge Question #8
"Why do you think that mainly adult manatees died from red tide and not young manatees?"

(To respond to this Challenge Question please follow the instructions at the end of this report.)

USFWS

Challenge Question #9
"If a female manatee is born in 1997, what is the earliest year that she could bear her third calf, assuming that no twins are born?

(To respond to this Challenge Question please follow the instructions at the end of this report.)

Paddles Away
It's time to bid farewell and thanks to Ranger Wayne Hartley. He reports that the manatee season at Blue Spring State Park is officially over for this spring. Not a single manatee has visited the hotsprings since February 27th. Every day since then, a grand total of "0" manatees have reported for his daily roll. Ranger Hartley doesn't expect them back until late October, when temperatures fall and the manatees seek warm waters again. Thank you Ranger Hartley--for sharing your knowledge with us, and for devoting your time to manatees!

How to Respond to Journey North Manatee Challenge Question # 8

1. Address an e-mail message to: jn-challenge-manatee@learner.org
2. In the Subject Line of your message write: Challenge Question # 8
3. In the body of the message, give your answer to this question:

Challenge Question #8
"Why do you think that mainly adult manatees died from red tide and not young manatees?"

How to Respond to Journey North Manatee Challenge Question # 9

1. Address an e-mail message to: jn-challenge-manatee@learner.org
2. In the Subject Line of your message write: Challenge Question # 9
3. In the body of the message, give your answer to this question:

Challenge Question #9
"If a female manatee is born in 1997, what is the earliest year that she could bear her third calf, assuming that no twins are born?

Don't Forget!

• Please do not answer both questions in one message!
• Please include the name of your school and your location so we can credit you properly for your answers.

The Next Manatee Migration Update Will Be Posted On April 16, 1997