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Data Czar Deliberations Looking at nest site selection of nesting Mama's using DNA ID



I tried looking at Turtle Maturity versus Nest Placement. Do more mature mother Loggerheads lay their nests further out of harm's way than say younger mothers? Relocating a nest is a human proxy for putting the nest IN harm's way. This is a hard theory to look at as we don't have the nesting turtles' ages. The closest we come to age is the DNA analysis that was done. The work on collecting egg shell samples and identifying the DNA goes back to about 2008/9. Each unique DNA/turtle is given a unique ID number. They can be identified year after year.


For example, one of the first loggerheads identified by DNA in 2009, on Cumberland Island, was CC000023 (CC are loggerheads). She nested exclusivity on Hunting Island in 2022 - 7 times!!!! 5 of those 7 nests were relocated. However just because she was identified in 2009 doesn't mean she is an old turtle. She could have been a "new recruit" (as the researchers say) that year - i.e. a first time mom. I don't have access to the DNA database so I don't know if they can tie the DNA to age, but I sort of doubt it. What they can do and have done is tie a family together. For example, they have identified a grandmother, mother and daughter from the same tree. So that particular grandmother is probably 70+ years old. I don't have access to that part of the database. I can only see what is tied to Hunting Island and even then it doesn't tell me about family trees.


In 2022, there was another turtle (DNA ID = CC015186) that nested 4 times on Hunting Island. 2 of those 4 nests were relocated. With a DNA ID in the 15,000+ range, that is a relatively new mother compared to CC000023 - maybe 10+ years older at a minimum. CC015186 is indeed a new recruit - according to the DNA work she was first identified when she nested on Hunting Island in 2022. So before that, she had not been seen nesting anywhere in the north region (NS, SC, GA). We don't know precisely how old one turtle is versus the other because the DNA work started in 2008-9. We can say the higher CC numbers, like the 14000 or 15000's are directionally younger mothers, because they were identified by DNA for first time in the last 5 years or so (as long we are not missing some sea turtles from the DNA analysis).


So the point of all this.....


I looked at the DNA ID for every sea turtle that nested on Hunting in 2022. There were 74 unique mothers that nested on Hunting. That was 175 nests. Of those, about 116 nests were relocated. Of those 74 unique mothers, 31 visited Hunting only once that year. I charted % relocation of all a mothers' nests versus their DNA ID number. The number is a proxy for age, but not a great one. Low DNA ID numbers are directionally older. High numbers are younger. What I see, again open to interpretation, is that "older" (more mature) mothers are NOT much different in their nesting habits than younger mothers. Again, this assumes that relocating a nest means the mother didn't keep her nest out of harm' s way - that is how humans view it. Based on this analysis of this one single year, albeit a big nesting one, I don't see a trend that says "oh, those older more mature turtles really understand how to place their nests out of trouble." Same statement holds for the younger mothers.


Bottom line.......I (maybe someone does) don't know how or why a mother picks one spot on a beach to nest versus another.


(PS the trend line shown on the chart is a running average for 5 turtles based on DNA ID)


All the best, see you soon


Keith


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