Navigation Links
Nesting Gulf loggerheads face offshore risks

DAVIE, Fla.-- Threatened loggerhead sea turtles in the northern Gulf of Mexico can travel distances up to several hundred miles and visit offshore habitats between nesting events in a single season, taking them through waters impacted by oil and fishing industries.

Evidence from a U.S. Geological Survey study challenges the widely-held view that sea turtles remain near one beach throughout the nesting season and suggests the threatened species may require broader habitat protection to recover. The findings also cast new uncertainties on current estimates of the size of the species' Gulf of Mexico subpopulation.

"This is the first study to locate and quantify in-water habitat use by female loggerheads in the Northern Gulf of Mexico subpopulation during their reproductive periods," said lead author Kristen Hart, a USGS research ecologist. "Our tracking results show they depend on a much broader range of habitat during this critical part of their lives than was previously thought to be required."

The study reveals detailed loggerhead movements during "inter-nesting" periods, showing patterns that vary for individual turtles. Generally, this period begins when a female returns from open seas around May and lasts roughly until September. Up until now, efforts to protect the species generally centered on beaches with high nesting activity under the assumption that once turtles had nested on those beaches, they either remained in their immediate vicinity or migrated back out to sea.

"The satellite data and our observations on the ground tell the same story: loggerheads in this subpopulation nest at multiple beaches, sometimes hundreds of miles apart," said Hart. "Some of the females we captured and tagged on beaches in Alabama traveled over 250 miles to nest in Florida, where we recaptured them. Likewise, we also captured some females in Alabama that had previously been tagged at the Florida site in earlier breeding years."

Researchers used the same statistical technique for analyzing their movements that enabled them to pinpoint loggerhead feeding hotspots at sea last year and, more recently, locate Kemp's ridley feeding grounds in the Northern Gulf by differentiating between behavioral modes. They analyzed where 39 adult female sea turtles went after they nested on beaches in Alabama and Florida between 2010 and 2012 to learn where they spent time in the water during the breeding season before migrating back to sea.

"We were surprised to find a lot of variation in their behavior," said co-author and USGS biologist Meg Lamont. "On average, the tagged turtles visited areas about 33 kilometers (20 miles) from shore and moved about 28 kilometers (17 miles) to nest at another beach. Several of them journeyed more than 200 kilometers (124) miles to nest at additional beaches, while others simply cruised back out to sea after the first nest."

The results of the study explain a mystery that had puzzled Lamont, who has 16 years of data from the St. Joseph Peninsula in Florida showing that few of the nesting loggerheads they tagged returned to nest again on the Peninsula. "We didn't know whether they were dying or simply nesting elsewhere," explained Lamont, "Now we know they aren't as faithful to one nesting site as was once thought."

One of the turtles that Lamont tagged in 2002 appeared at Hart's site in Alabama, nearly a decade later. In fact, the researchers saw several turtles nesting both in Alabama and the St. Joseph Peninsula (roughly 250 miles apart) within a period of just two weeks.

"These data show it is not sufficient to just protect habitat around high density nesting beaches such as the St. Joseph Peninsula because many turtles that nest on the Peninsula use the entire region from the eastern Florida Panhandle to Louisiana," said Lamont.

There could also be fewer female loggerheads nesting in the northern Gulf of Mexico than current estimates suggest because they are calculated using nest numbers. "Our research shows that the same turtle could easily deposit eggs in Alabama and Florida if nests are separated by about 2 weeks," said Hart. "Population numbers based on nest counts may therefore be biased upwards if nests at the two sites were assumed to have come from two different females."

The study also noted that the areas the loggerheads used during the inter-nesting period overlapped with human uses, such as shrimp trawling and oil and gas platforms. A map showing sea turtle habitat use in relation to these activities can be found in the article, "Movements and Habitat-Use of Loggerhead Sea Turtles in the Northern Gulf of Mexico during the Reproductive Period," which was published July 3 in the journal PLOS ONE.

"We are working towards defining areas where sea turtles concentrate their activities at sea, effectively building a map of in-water turtle hotspots," said Hart. "The more we know about their habitat use, the more questions are raised about their behavior and ability to adapt. We hope to build a better understanding of how frequently turtles return to these same locations, and whether or not they move to new habitats when those locations are impacted. This type of information would be extremely valuable for developing management strategies to help in population recovery."


Contact: Hannah Hamilton
United States Geological Survey

Related biology news :

1. Study provides insight into nesting behavior of dinosaurs
2. Gannets could be affected by offshore energy developments
3. Study finds circle hooks lower catch rate for offshore anglers
4. NOAA science supports New Yorks offshore energy planning
5. Aerial mosquito spraying study finds no immediate public health risks
6. New research identifies risks, interventions for childrens GI health
7. Agencies should use common approach to evaluate risks pesticides pose to endangered species
8. Energy efficiency could increase infection risks in hospital wards
9. Fossil study helps pinpoint extinction risks for ocean animals
10. Ecologist: Genetically engineered algae for biofuel pose potential risks that should be studied
11. Cut emissions further or face risks of high air pollution, study shows
Post Your Comments:
(Date:11/18/2015)... 18, 2015 --> ... new market report titled  Gesture Recognition Market - Global ... - 2021. According to the report, the global gesture recognition market was ... to reach US$29.1 bn by 2021, at a CAGR ... North America dominated the global gesture recognition ...
(Date:11/17/2015)... Mass. , Nov. 17, 2015 Pressure ... leader in the development and sale of broadly enabling, ... worldwide life sciences industry, today announced it has received ... its $5 million Private Placement (the "Offering"), increasing the ... $4,025,000.  One or more additional closings are expected in ...
(Date:11/12/2015)... --  Growing need for low-cost, easy to use, ... the way for use of biochemical sensors for ... clinical, agricultural, environmental, food and defense applications. Presently, ... applications, however, their adoption is increasing in agricultural, ... on improving product quality and growing need to ...
Breaking Biology News(10 mins):
(Date:11/25/2015)... SAN DIEGO , Nov. 25, 2015 ... that management will participate in a fireside chat discussion ... New York . The discussion is ... Time. .  A replay will ... Contact:  Media Contact:McDavid Stilwell  , Julie NormartVP, Corporate ...
(Date:11/25/2015)... , November 25, 2015 ... Report is a professional and in-depth study on ...      (Logo: ) , ... the industry including definitions, classifications, applications and industry ... for the international markets including development trends, competitive ...
(Date:11/25/2015)... Francisco, CA (PRWEB) , ... November 25, 2015 ... ... microbial genomics company uBiome, were featured on AngelList early in their initial angel ... launching an AngelList syndicate for individuals looking to make early stage investments in ...
(Date:11/24/2015)... KUALA LUMPUR, Malaysia , Nov. 24, 2015 ... the global contract research organisation (CRO) market. The ... to result in lower margins but higher volume ... With increased capacity and scale, however, margins in ... Contract Research Organisation (CRO) Market ( ...
Breaking Biology Technology: