Tracking Gilda

GILDA’S TRACKING STATISTICS

Release Date: 5-12-2010
Transmitter Type: Wildlife ComputersMK10-PAT
Data Collected: Location ,Water Temperature, Dive Depth, and Light Level
Expected Lifespan of Tag: 300 Days

Distance From Juno Beach: 1563Kilometers (971miles)
Estimated Total Distance Traveled: 1735 Kilometers (1078 miles)
Current Water Temperature: 22.4°C
Nearest City: Normandy Beach, NJ

 

Click map to download PDF.

11/10/2010 – Gilda’s Final Update

Gilda stranded on October 8th, 2008 in Port Everglades with injuries consistent with those from a large boat propeller. The injuries affected both of her front flippers, resulting in the complete amputation of her right front flipper and fractures of the radius and ulna of the left front flipper. She also received deep lacerations to the neck and face. Gilda required blood transfusions and orthopedic surgery.  Orthopedic bone plates were placed on the broken bones in Gilda’s left front flipper to aid in healing. These plates were removed after the fractures had healed. Gilda’s condition was extremely guarded for several months after arriving at Loggerhead Marinelife Center (LMC). She required a feeding tube to receive nutrition and she did not begin eating on her own until 5 months after arriving. Gilda required extensive physical therapy to strengthen her damaged front flipper. After months of physical therapy at the LMC, she was transferred to the Clearwater Marine Aquarium for additional therapy in a larger, deeper tank that allowed her to become accustomed to her swimming abilities with one front flipper.

Gilda’s case provided us with many learning opportunities. Researchers at the LMC decided to try to study Gilda’s post-release behavior, especially given her compromised state. A satellite tracking tag was selected that would monitor Gilda’s location in addition to her diving behavior, allowing us to track her post-release status.

We purchased a Wildlife Computers Popup Archival Transmitting (PAT) tag, that monitors location from satellite triangulation of signals (termed Argos locations), dive depth, water temperature and light level (a less accurate but alternative way to measure location).  Recent data are transmitted back to us via ARGOS satellites as the turtle surfaces normally to breathe.  The tag has a break-away device that can be programmed to release the tag from the turtle at a set time or under specific conditions.  At the time of tag release, the full data set can be transmitted if the battery has sufficient reserve power.  The conditions under which a PAT tag will release from the turtle, float to the surface, then transmit its stored data are: the turtle stays at the same depth for a prolonged period of time selected by the researchers, the turtle remains at the surface for a prolonged period, the tag encounters a force that pulls it from its attachment site, or the tag reaches a release date designated by the researchers.  Thus the tag allows us to determine if the turtle is behaving normally, abnormally, or is likely deceased (at the same submerged or surface depth for a prolonged period of time).

TRACKING AND TIMING OF EVENTS
Gilda was released from the beach near the LMC on May 13th, 2010. Her PAT tag was attached to her shell using standard procedures for loggerhead turtles.  The tag was set to send data every day for three days and then switch to once weekly. Gilda’s tag sent transmissions on all but one of her scheduled days until June 24th when transmissions ceased. We did not receive any additional information from Gilda until September 7th, when her tag began sending the entire archive of its data, indicating it had released from the turtle prematurely. Analysis of the tag data indicated that the tag collected samples regularly until July 17th, when the depth sensor began to record a constant reading, indicating it was at the surface. On July 25th, the tag released itself after spending 8 days at the surface.  The tag should have sent its full data at that time, but it did not.  It is unclear why the data transmission was delayed until September 7th (see possible explanations below).  When the tag sent its data, the battery power was sufficient only to transmit the complete archived data through June 15th.  The available dive data after June 15th are “snapshots” and not as detailed as we would like.  Thus, we only are able to classify how much of the day Gilda spent at specific depths.

Immediately following her release, Gilda remained fairly close to the Florida coastline. Her last recorded location was northeast of Cape Canaveral on June 10th.  Dive information recovered from Gilda’s tag indicates that she was diving normally. Gilda averaged 20-60 minute dives and spent anywhere from 1 to 45 minutes at the surface during the first few weeks after release.  From June 12-15, Gilda underwent several extremely long dives, lasting for many hours, with short surface intervals. She returned to a normal diving pattern shortly after this, with much shorter and shallower dives.

Locations based on light levels and water temperature data show that Gilda travelled north along the Gulf Stream and entered coastal waters near New Jersey on July 15th. From July 18th to July 25th, the depth sensor recorded constant reading at the surface.  Her diving behavior just prior to July 18th was normal.  On July 25th, the tag released itself from the turtle.  At this point, the release pin on the tag was intact, indicating that the tag had still been on the turtle; it had not broken off and floated free.  However, the tag did not transmit its information right away as was expected.  There are several reasons why this may have occurred.  It is possible that the tag became trapped beneath debris at the surface, preventing the antenna from breaking the water’s surface and transmitting data until it was freed.  Another possibility is that the tag experienced sufficient growth of fouling organisms (such as algae and barnacles) that the mechanism (transmission switch) that detects when the antenna is exposed to air was temporarily disabled.  Thus the tag would not “know” to transmit until the fouling organisms died or were knocked away. This explanation is consistent with why we received no ARGOS location transmissions after June 24th even though the data later transmitted by the tag show that she was swimming normally until July 17th.  Whatever had been fouling the transmission switch could have been killed by a change in temperature, marine animals could have ingested the organisms, or high surf could have knocked loose debris, freeing it from the tag.

All indications are that Gilda was behaving normally and her rehabilitation was effective until something caused her to float at the surface beginning July 17th.  All of the remotely recorded data relayed by satellite indicate that Gilda stopped diving and remained at the surface until her tag released on July 25th very near the coast of New Jersey, USA. Based on all gathered data and our interpretation of those data, we believe that Gilda was behaving normally in an area known to have a high mortality risk for loggerhead sea turtles. This is an area known to be very active with bottom trawl fisheries.

While Gilda’s story is a remarkable one with an uncertain ending, we learned a great deal from her that will help us with future patients. We suspect that Gilda’s initial success was due to the care given to her, including physical therapy and extensive rehabilitation. In our opinion, we cannot say with 100% certainly what the fate of Gilda was, but in our hearts she will always live on.

8/1/2010

Where is Gilda? Did her transmitter break? Is Gilda OK?  – Those are great questions, and ones that we are not able to answer right now.  On 6/10/2010 Gilda was located northeast of Cape Canaveral (29.169, -80.22) and heading to the north.  Before her last transmission, she was behaving like a normal turtle and making “Square” shaped dives to an average of 23 meters deep that lasted an average of 36 minutes each.  This is normal loggerhead turtle behavior and it is very encouraging to us given the state of her injuries during rehabilitation.

Gilda’s transmitter was designed to understand mortality events and is most often attached to pelagic fish.  The attachment to sea turtles is a rather new technique and has been successful on both juvenile and adult loggerhead turtles.  Her transmitter is programmed to “check –in” weekly each Thursday before releasing 300 days after deployment.

This “check-in” will be very rare due to the fact that it is dangling behind her and only very briefly (or not at all) at the surface in order for the data to be received by the passing satellites.  The fact that we are not receiving data is NOT necessarily a bad thing!  If this turtle were to be injured further or even die, her transmitter is smart enough to release itself and relay an archived set of data. We will know her true story when the tag is scheduled to release on 3/8/2011.

6/10/2010

Gilda has indeed moved offshore! She is now located north of Cape Canaveral near the boundary of the warm waters of the Florida Current and the cooler waters near the coast of Florida. She is currently spending her time diving to depths of more than 30 meters and spending 30 seconds to a minute at the surface between dives.

6/5/2010

Gilda has moved into deeper and cooler water which may indicate that she has moved offshore. She is currently spending time in waters that are ranging from 6.8 to 9.3 meters. Given the deeper depth, we can expect more locations from her as she should be spending a bit more time at the surface between dives. Be sure to check back for next weeks update!

5/28/2010

Gilda’s tag transmitted on schedule on Thursday May 27th and we received some high quality data which included an estimated location. While the quality of the location is not very high, we believe that Gilda is currently in the Indian River Lagoon system south of the Ft. Pierce Inlet. She is spending much of her time at the bottom which is about 2.5 meters deep and is only at the surface for two or three seconds between dives. Where do you think Gilda may be heading next? Check back next week for an update.

5/21/2010

Gilda checked in as planned on Thursday the 20th. We did not receive a location during this check in but she appears to be behaving normally based on temperature, depth and dive profile data received from her tag. The water temperature where she is currently swimming ranges from 18 to 22 degrees celcius and the average water depth throughout the past three days is 2.6 meters. Where do you suppose she is? Gilda will send transmissions each Thursday. Check in with us again next week for more Gilda updates!

5/12/2010

Gilda was released tonight off Juno Beach and seemed very happy to be back home in the ocean. Her first transmission map is above, look at how far she has traveled already.