What impacts loggerhead sea turtle hatch success?

Methods

Summary

After a loggerhead nest is detected and confirmed by the presence of a clutch of eggs, all eggs are removed from the nest. Eggs are counted during removal and placed into a bucket with cool, wet sand. After all eggs have been removed, half are returned to the nest. At this point, a HOBO data logger is attached to a string and is placed into the nest. The remaining half of the eggs are replaced into the nest. The nest is then covered with sand. The data logger is set to record temperature in the nest every 30 minutes throughout incubation. 

Vegetation: A 1m X 1m quadrat with 100 sections is placed over the center of the nest and vegetation percent cover is counted. At the end of incubation, vegetation is counted in the same way and pictures are taken in order to identify established plant species.

Moisture: Moisture is measured using a Aquaterr EC-350 digital soil moisture, temperature, and salinity meter. Moisture is measured when the nest is discovered, periodically throughout incubation, and when nests are inventoried at the completion of incubation.

Tidal inundations: Every nest is checked daily throughout incubation. If a nest was washed over by any tide since it was last checked, the date of the inundation for that nest is recorded. 

Dune morphology: The dip and strike are recorded for the dune where each nest in the sample is located using a Brunton Induction-Damped Standard Pocket Transit.

Elevation: Elevation was measured using a RTK GPS system. 

Challenges

It is a daunting task to measure moisture on every nest regularly throughout incubation. The equipment can take awhile to calibrate which proves to be an issue because I would like to take all moisture measurements in the morning before the sun greatly impacts temperature and moisture. 

Feral hogs ravage the island and tend to be a problem for turtle nests--they often consume entire nests either as eggs or hatchlings. There is a DNR staff member on the island who aids in hog eradication and generally helps keep nest depredation low.