Predators can have a severe impact on rare and endangered species through predation and competition. One of the primary threats to endangered sea turtle reproduction in Florida is nest predation by raccoons and armadillos. Recently, NWRC researchers and federal, state and private sector partners reported on the effectiveness of removing nest predators from key sites to increase the survival rate of sea turtle nests and other beach dwelling threatened and endangered species. The most recent findings in an article titled, “An Ideal Combination for Marine Turtle Conservation: Exceptional Nesting Season, with Low Nest Predation Resulting from Effective Low-Cost Predator Management,” will soon be published online in Oryx: The International Journal of Conservation. In this study, predation damage management efforts in 2008 at the Hobe Sound National Wildlife Refuge (HSNWR) in Florida resulted in more than 128,000 additional sea turtles emerging from nests compared to previous years when no predator management occurred.
“On many beaches, predation is one of the greatest threats to sea turtle eggs and nesting success. We found the management of predators, such as raccoons and armadillos, at key sea turtle nesting sites significantly boosts the survival of sea turtle nests and the number of emerging hatchlings,” said NWRC biologist and biometrician Dr. Rick Engeman.
The HSNWR on Jupiter Island is a critical nesting beach for threatened and endangered sea turtle species. In 2008, the threatened loggerhead sea turtle and the endangered leatherback, green and Kemp's ridley sea turtles nested at HSNWR. The beach has a long history of nest predation by raccoons and invasive nine-banded armadillos, with several other species having lesser impacts.
Prior to implementing a formal predator management strategy at HSNWR, up to 95 percent of turtle nests were destroyed by predators. While the refuge management is unlikely to influence the number of sea turtle nests deposited, the study showed it can dramatically influence the success of those nests.
In a similar effort , NWRC and the Florida Department of Environmental Protection examined the impacts of predator management on sea turtles and least terns on two adjacent barrier islands along Florida's west coast. Cayo Costa and North Captiva both suffered severe nesting losses for sea turtles and shorebirds due to predation and disturbance by raccoons, while Cayo Costa also was impacted by invasive feral swine. Prior to predator management conducted by Wildlife Services operations, no least terns successfully nested on either island, and sea turtle nest predation was 74 and 60 percent, respectively for Cayo Costa and North Captiva.
In 2007, predator management occurred on Cayo Costa, while North Captiva provided an unmanaged comparison. Later that year on Cayo Costa, 31 least terns hatched and sea turtle nest predation was only 15 percent. In contrast, North Captiva again had no least terns and sea turtle nest predation was 84 percent. In 2008, both islands received predator management, and the results were positive again with 20 and 55 least terns hatched and 16 and zero percent sea turtle nest predation on Cayo Costa and North Captiva, respectively. The cost for predator management on the islands was $39,636, while the returns associated with the increase in least terns and sea turtles were valued at over $1.1 million.
These publications are the latest in a 10-year history of research on protecting sea turtle nests on Florida's beaches. The research not only documented the efficiency and benefit-costs of management actions, but also defined the optimal times and placement strategies for the management. In HSNWR alone, these actions have resulted in the emergence of well over a half million additional hatchling sea turtles since 2001.
* Photo from the Sea Turtle Conservancy
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