Spent some time looking at DNA. Here is edition 1.
Some Background - DNA analysis of sea turtle tests on HI began in 2010. The first year for DNA testing in the northern recovery region was 2009. Conversely I believe government funding for the DNA program ran out in 2023, leaving about 55 HI nest samples from 2023 not analyzed (see the separate request for private funding by HI friends). This means drawing certain conclusions pre-2014 or on/after 2023 will be more difficult. As various beaches wind down on private funding, and hence analysis, the ability to track mother sea turtles across beaches will likely cease. If that lack of funding continues in the northern region, I personally don’t think it will be really worth it collecting DNA samples on HI in the future – this is my personal opinion only.
First a definition: “Unique females” on HI - these are the individual female turtles that nest on HI in a given year, as identified by DNA. A female can lay 1 or 7 nests on HI. We actually had 1 turtle in 2022 that laid 7 nests on HI (more later on that).
In 2023 HI reached a high of 77 unique females, even with only 72% of nests analyzed for DNA. If we try to extrapolate to all 100% of the record 195 nests analyzed, the number might be closer to 97-107 unique females.
The average number of unique females in a year, since 2010, is 50% of the nests analyzed for DNA. The highest % of unique females was actually in 2018 at 68%, with a low of 42% in 2022. Looking at the same numbers a little differently, there were 60 nests in 2018 and with 41 of those being unique females, they delivered a staggering low 1.46 nests per female on HI. The highest delivery of nests on HI was in 2022 when it hit 2.37 nests per unique female. The average since 2010 is right around 2 nests per females every year.
So far in 2024 we have 126 nests, which would seem to indicate there were about 63 unique females who visited HI so far. In all of SC, the average delivery is between 3-4 nests/females/year. I couldn’t find any SC beach above a 3. Why is all of SC higher than the individual beaches? The 3-4 nests/year does not include the nests that SC unique females lay on beaches outside the state (GA, NC, FLA).
Contrary to the 3-4 nests per turtle we saw above, as a general rule let’s go with a nesting turtle laying 3-6 nests in a year, with a 10-15 day gap between nests. The nests per unique females clearly indicates that nesting female turtles are not exclusive to their birth beach. They seem to wander around some and have hit different beaches on the way to/from their home beach (maybe food, weather, tides, obstructions, mating grounds, etc). Looking at unique females gives us a good idea of overall female population in the region. The number of unique females generally trends with number of nests. Makes sense. It certainly doesn’t tell us about future nesting trends on HI, at least to me it doesn’t. As long as the future number of unique nesting females increases overall, that’s good!
Back to our turtle that laid an incredible 7 nests on HI in 2022. This is female turtle CC000023 whom is one of those unique females. The ID number indicates she was one of the first females ever identified by DNA under the program. This unique female was first identified in 2009 on Cumberland Island in Georgia. She was only identified twice that year, both times on Cumberland. This doesn’t mean she did not nest more that year. It could mean she came to HI in 2009, but since we weren’t doing DNA samples that year, she was “missed”.
Since 2009 she has nested almost exclusively on HI in 2012, 2016, 2019 and in 2022. I say almost exclusively as she did nest on Hilton Head twice in 2012, but since then she has been extremely loyal to HI. Her timing between nesting seasons is 3, 4, 3 and then 3 years. She may have nested before 2009 on HI but the DNA program was not active then.
She is also a very active nester. Except for 2009, she has laid at least 6 nests every year she came ashore. I say this with one caveat as there were only 5 nests identified in 2019 but there was a possible missed nest for her that year. There was a large 23 days gap between her identified nests in June. There was a nest on HI on June 9th that was not analyzed for DNA. This may have been her but we will never know for sure. I have no idea why the DNA was missed on this one. Maybe a missed or spoiled sample.
I have no idea how old this unique female is. The Shamblin team may and they may even know if she has DNA identified daughters and granddaughters.
Our loyal HI turtle CC00023, what biologists call “high fidelity”, has laid 26 nests in 2 states on 3 beaches since she was first identified by DNA. Of those 26 nests, 22 were on HI. There may have been more nests prior to DNA testing and she lays fairly successful nests in terms of hatchlings and with an eyeball average of about 120 eggs in each clutch.
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