Costal Wetlands Ecosystems of SWFL, Part 4, Turtle Nest and Gender Assignment

While walking along a very low traffic area on the southern end shoreline of Fort Myers beach, turtle activity was easily seen. The nest was two meters inside of the bird restricted area. A closer investigation was ill advised. The turtle traveled about 40 meters from the shore in the early morning to lay her eggs, bury them and then returned to the sea. There was no sign of other human traffic in the area. The picture was made at approximately 9:00 AM.

The Green sea turtle in the feature image was made in the Caribbean in a reef system 5 miles off of the coast of Belize.

For a more comprehensive description of instrumentation see the previous posting on Soil Thermometer Exploration. Also see Costal Wetlands in SWFL Part 2

Path from shore to nest appears to be from a green turtle. There is no center tail track between the fin marks.
Soil temperature 26.4 C, 3 meters from nest at 20 cm depth.
Sea turtle egg nest recently buried
Green Sea Turtle 80 feet under water, in reef 5 miles off the coast of Belize.

Using my foot print in the sand as a reference you can see that the path is little wider than one meter (~120 cm). Turtle fin prints have an alternating step pattern and there is no central groove in the sand in the center of the track between the fin prints. The more common turtle here would be the Logger Head. The markings of this track suggests that this was made by a Green Sea Turtle. Considering the activity, the distance from the water, the opening a hole in the sand, the laying of estimated 80 eggs, the covering of the eggs with sand and the returning to the water, this experience must have taken at least two hours. There were no other predator foot prints on the sand.

Proposed research:

Observation: Sea turtles and apparently many reptiles exhibit temperature dependent sex determination (TDSD)*. A sufficient level of research on TDSD has been done. My recordings over the last two days in nearby sand areas at various times suggest that the sand temperature should rise from the noted 26.4 C to a higher temperature between 29 C and 31 C by mid day. If the average temperatures remain in that range or lower during the entire day, there should be significantly more than 20% male offspring. With the knowledge from previous research the more appropriate prediction would be at least 80% female hatchlings.

There is a problem with failure to have gender diversity from turtle hatchlings on the beaches of Florida***. Findings in Florida beaches show abnormally high percentage of female hatchlings. This is apparently the result of average higher temperatures. It is also projected that with rising temperatures the shortfall in the male population will result in a colony population insufficient to sustain its current level. I suggest a simple attempt to reverse the gender trend. Here is a pilot project proposal:

Purpose: Is it possible to control sand temperature thereby controling the gender of turtle hatchlings at the beach?

The null hypothesis: The sand temperature at a depth equal to or greater than 20 cm would rise to 30 C or more for a significant period during the day regardless of attempts to stabilize it.

Method: Measure the change in sand temperature in a specific location of costal beach. It should be continuously recorded relative to change in time consistent with a projected egg incubation period. Include the variables of a specified period of the year and selected location. Test an interventional variable such as application of a controlled volume of sea water to the surface of the sand in the test location. The water volume should be less than the absorptive capacity and capillary action of the sand below 10 cm.

Discussion: If the null hypothesis is disproven and data revealed a regular pattern of temperature stabilization within a specific range at a depth of 20 cm, one should be able to predict the male / female ratio of the expected hatchings**. If this research shows a favorable result there may be a remedy for the diversity shortfall. Proactively, the genetic population of the nest might be regulated by cooling the nest through the timely addition of a controlled volume of water. The effect of the water would be immediate cooling of the surface and a delayed effect resulting from water evaporation. If this is effective it would thwart the risk of having an excess of female turtles or an insufficiency of male turtles. If this pilot study shows benefit this may be applied to a larger area such as selected nests along several miles of beach. A volunteer effort could support this type of effort. Please read the thought provoking references below.

If you are interested in the effort to support gender diversity in the turtle populations please share your comments.


*TDSD via STAT phosphorylation at the warmer, female-producing temperature

**Figuring out the genes that let reptiles use temperature to determine sex

***Hotter summers mean Florida’s turtles are mostly born female

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#turtles #nest #temperature #reptile #gender #TDGD #sand #beach #thermometer #eggs #reptile #population

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