Sunday, April 17, 2016

The Great Migrating Loggerhead Sea Turtles & Their Quest for Conservation

The Loggerhead Sea Turtles are a great migrating sea turtle in the Atlantic Ocean and are found at the Outer Banks. As we talked about in class, they ride the Gulf Stream Current up to mating areas and ride the Canary Current back to the U.S. coast to lay their eggs and forage. By riding these currents, they cruise more swiftly to the areas they desire to be at. 

Turtle migration patterns are an important area to study in marine biology because of the drastic decrease in sea turtle population numbers. Understanding their migration patterns and behaviors can help us to find ways for better conservation. As mentioned in class, all of the seven marine sea turtle species are either endangered or threatened. Finding ways to recover these populations is the desired goal in this study.
Photo Cred: Michael Melford, National Geographic

Caretta Caretta
This study wanted to know better ways to conserve and recover the Endangered Loggerhead Sea Turtle populations. To better understand this process, they set up an experiment to study the migration and foraging patterns of 68 Loggerhead female turtles. This study was done between 1998-2008 by DuBose B. Griffin and many other authors. 
Photo Cred: Sea Turtle Conservancy

They tagged the female Loggerhead's with platform transmitter terminals at nesting beaches in Georgia, North Carolina, and South Carolina. They viewed the movement of these turtles by satellite and observed for patterns. 42 of the 68 Loggerhead's used migration patterns along the continental shelf. 4 of those 42 turtles made excursions but eventually returned to the shelf and foraged in those areas. 2 of the 42 ventured off all the way to the Bahamas. 3 of the 42 left the shelf during winter and returned in summer and 1 out of the 42 left the shelf in November and returned in February. They noticed that these turtles had a very unique migration route that was not seen in any other marine sea turtle species. Most importantly, they saw that these 42 migrated north of Cape Hatteras between May and October. This shows a distinct migrating and foraging behavior in the warmer months. Then in the colder months of winter, migration and foraging patterns switched and became more southern focused.

Photo Cred: DuBose B. Griffin Paper

This figure from the paper shows the movement along the latitude throughout the months of the years averaged between 1998-2008. They observed a pattern for migration. Section A shows the Post-Nesting Migration Segment. Section B shows the North to South inter-foraging migration segment. Section C shows the South to North inter-foraging migration segment. We can see that the movements are relatively consistent and showed that all of the foraging areas were off the continental shelf. This figure shows the switching of migration from the Mid-Atlantic Bight to the South-Atlantic Bight during different seasons. 

On top of the migrating patterns found in the Loggerhead's, they also found distinct foraging areas that the turtles used in 63 of the 65 turtles. Over a long time span, consistency is a great finding for conservation strategies. They also took notice that male Loggerheads and Green Sea Turtles also foraged in the same areas although migration patterns were not measured. They found that there were distinct spots on the continental coast where they were foraging and nesting and it was not just on any part of the shelf or beach. This makes this study very successful in bringing very specific locations for conservation. One of the most important findings was that the Loggerhead migration patterns seemed to line up with the migration patterns of commercial fish that are known to kill large numbers of these turtles annually. From our past studies in class on the long lives of turtles and low success rate of hatched babies, this is something to consider. 

As it is a great discovery to find specific migrating patterns and foraging locations for these female Loggerheads, it is also dangerous to know its co-alignment with its predators. Conservation strategies are in place to help protect these species as this paper was published in 2013. Why they migrate in predator filled waters and have not adapted to a new migrating pattern is unknown and is to be further researched.

Griffin, DuBose B. 2013. Foraging habitats and migration corridors utilized by a recovering subpopulation of adult female loggerhead sea turtles: implications for conservation. South Carolina Department of Natural Resources. Retrieved from Academia on 17 April 2016. 

1 comment:

  1. What is the commercial fish species that feeds on these turtles?