Boca Raton’s Beaches Host Above Average Sea
Turtle Nesting Activity in 2015
Kirt Rusenko, Ph.D., Gumbo Limbo Nature Center
The sea turtle nesting results for 2015 were very good in terms of the number of nests deposited in Boca Raton by the greens, leatherbacks, and loggerheads. The nests for all three species totaled 1041 which is significantly higher than the 29 year average number of nests which is 802. The loggerheads slightly bettered the 29 year nest average of 708 by totaling 718 in 2015. This number is higher than the average number of loggerhead nests from 2000 to 2009 which is 495 and is consistent with the increase in loggerhead nesting we have seen since 2010. This trend is also being seen statewide! Our green sea turtles had another outstanding year smashing the 29 year average of 82 nests with 298 nests in 2015. These turtles have demonstrated an amazing comeback in recent years with their nesting numbers increasing exponentially in Florida. Contrast this with the 15 to 30 nests we had in Boca Raton in the late 1980’s! Leatherbacks have also been demonstrating healthy increases in nesting, they are the least numerous nesters in Boca Raton as well as Florida, their 29 year nest average for Boca Raton is 12 nests and we more than doubled that number in 2015 with 25 nests. Leatherback nest numbers are also increasing exponentially in Florida but not at the pace of the green turtles.
Unfortunately, more nests did not equate to more hatchlings in 2015 even though the season had only one minor tropical storm with relatively few nests washed out by erosion. The number of eggs that hatched in the 2015 nests plummeted compared to previous years for all three species. Loggerhead nests in 2015 only had 54% of their eggs hatch compared to the average hatch percentage of 82% for the 2012 to 2014 nesting seasons. This is a huge drop in nest productivity! The greens fared slightly better in 2015
Unfortunately, more nests did not equate to more hatchlings in 2015 even though the season had only one minor tropical storm with relatively few nests washed out by erosion. The number of eggs that hatched in the 2015 nests plummeted compared to previous years for all three species. Loggerhead nests in 2015 only had 54% of their eggs hatch compared to the average hatch percentage of 82% for the 2012 to 2014 nesting seasons. This is a huge drop in nest productivity! The greens fared slightly better in 2015
with a drop to 68% compared to the 2012-2014 average of 77%. Leatherbacks had the largest drop in the percentage of eggs to hatch dropping to 40% hatched in 2015 compared to the 2012-2014 average of 66%.
The reason for this may well be the dry weather we experienced early to mid-season. Nests with temperature dataloggers in them were indicating incubation temperatures exceeding 38 degrees C (100 degrees F).
The reason for this may well be the dry weather we experienced early to mid-season. Nests with temperature dataloggers in them were indicating incubation temperatures exceeding 38 degrees C (100 degrees F).
These temperatures exceed the accepted lethal temperature of 34 degrees C (93 degrees F); this is the temperature at which an incubating egg should not survive to hatch. On the beach we noticed the layer of dry sand over the nests was increasing in thickness as the weather remained dry. In some cases, the dry sand reached the top of the egg chamber resulting in about 25 nests that had no egg hatch at all. Scientists are expecting to see impacts of climate change affecting most species on the planet (with the exception of the hydrothermal deep-sea vents). Increasing numbers of sea turtle eggs literally cooking during incubation may be one small impact of climate change, 2015 is proving to be an abnormally warm year as well.
The final negative is that we are seeing more evidence of human activity on the beach at night and not all of the activity is benign. Most distressing are the large number of fires on the beach at night. Lighting fires on the beach is not only illegal; it can directly cause the death of emerging hatchlings by serving as a light source that attracts them. There have been many cases of burned hatchlings found in the ashes of beach fires; the light of the fire draws them right into the flames. If you are on the beach at night, please do not start fires or use a white light flashlight, and limit use of cell phones as the light from the screens can also attract hatchlings. Do not approach a sea turtle on the beach as that may scare her back into the ocean where she may drop her eggs in the ocean instead of the sand.
