Some unexpected findings during the genetic tagging of sea turtles revealed the prevalence of mother and daughter turtles nesting at the same time.
“It’s something we never anticipated,” said Matthew Godfrey, North Carolina Wildlife Resources Commission Biologist. Godfrey presented his findings during the 2012 North Carolina Beach Inlet and Waterways Association conference, held at the Blockade Runner Beach Resort on Nov. 19-20.
The average age of maturity for loggerhead sea turtles is 30 years, Godfrey said. If a mother and daughter are nesting at the same time, the mother must be at least 60.
The higher-than-expected prevalence of siblings nesting in the same area was also surprising. With only one out of 1,000 sea turtles surviving into adulthood, it seems unlikely that two siblings would survive and nest in the same region. This finding suggests that genetic factors may play a role in deciding which turtles survive.
The national recovery plan for loggerhead sea turtles, which was last revised in 2009, lists the species as threatened in the Northwest Atlantic. The plan for the region set the goal of 2,000 nests per season. The number of nests found each season currently averages around 750. Godfrey said to reach the goal of 2,000, wildlife officials are hoping to see a 2-percent increase in nests found during the next 40 years.
One of the most telling indicators of the species improving is the number of nesting females; however, with so much coastline to cover and so few volunteers, it’s hard to locate them all. Godfrey and his team have found a way to identify the nesting females based on the eggs they leave behind.
Eggs are constructed layer by layer inside the oviduct of a mother turtle. As the layers grow, cells from the mother’s oviduct rub off and are trapped underneath them. After removing one egg from each nest, which averages 120 eggs, Godfrey and his team peel back the egg’s layers to identify 18 alleles from the trapped oviduct cells to create a genetic identification for the turtle.
This genetic identification is used to gather information about a variety of aspects of the turtle’s nesting behavior, including the number of nesting females in the region, nest site fidelity and internesting intervals.
Since 2009, the project has sampled 2,954 nests and identified 828 nesting female loggerheads. It has determined the average number of nests per season, per female turtle is three and the internesting interval is about 15 days. The project costs approximately $200,000 per year, and is funded by the National Marine Fisheries Service.