1. It’s Raining Male Hatchlings: But At What Cost To Emergence Success?
Jill Schmid1 and Dave Addison2
1Rookery Bay National Estuarine Research Reserve
2The Conservancy of Southwest Florida
ABSTRACT
Incubation temperature of loggerhead turtle nests have been recorded on Keewaydin Island, Collier County, Florida since Over the course of the study, decreases in incubation temperature were observed in association with rain events but precipitation amounts were not recorded. Many of the nests impacted by rainfall were predicted to produce male hatchlings based on average incubation temperature during the thermosensitive period. However, these nests had reduced emergence success due to the detrimental effects of storm events (i.e., high tides and erosion). An automated rain gauge was incorporated into the study during the 2010 nesting season, in order to gain a better understanding of the effect of precipitation on incubation temperatures and hatching success. During the past 4 years of the study, there were 316 HOBO temperature data loggers deployed in situ nests which recorded hourly temperatures for the duration of the incubation period. The past 4 years have had very different weather scenarios. The 2010 and 2011 sea turtle nesting seasons were uneventful in terms of storm impacts and precipitation. The 2012 nesting season was severely impacted by Tropical Storm Debby and Hurricane Isaac which washed out many of the nests. The 2013 season was very wet but lacked tropical storm impacts. These efforts will be continued in the future in order to gain a better understanding of the effects of precipitation on incubation temperatures, hatchling sex ratios, and emergence success under different weather scenarios.
Figure #. Average sand temperature and daily precipitation totals during the 2012 nesting season. 6/23 = Tropical Storm Debby, 8/26 = Hurricane Isaac.
Figure 1. Location of Keewaydin Island, Florida.
Figure #. Average sand temperature and daily precipitation totals during the 2013 nesting season. No name storms but frequently daily rain.
MATERIALS AND METHODS
Study Area
Keewaydin Island is an unbridged, 12 kilometer long primary barrier island, located south of Naples, Collier County, Florida (Figure 1). Approximately 85% of the island is owned and managed by the Florida Department of Environmental Protection (FDEP) and is within the Rookery Bay National Estuarine Research Reserve (RBNERR).
Incubation Temperature and Rainfall Data
A HOBO® (Onset Computer Corporation, Pocasset, MA) rain gauge data logger (Figure 2) was deployed on Keewaydin Island in 2010 to record rainfall events and air temperature for the duration of the sea turtle nesting season. HOBO® H8 and Pendant temperature data loggers were deployed opportunistically in situ nests on Keewaydin Island to record hourly incubation Additionally, six reference temperature data loggers were deployed at 30 cm along the dune to record sand temperature throughout the nesting season. *
Figure #. Average Incubation temperature and Total Precipitation by Year
Figure #. Average Emergence Success and Total Precipitation by Year
2010
7/23 – Tropical Storm Bonnie
8/9 – Tropical Depression
2011
8/23 – Hurricane Irene
2012
6/23 – Tropical Storm Debbie
8/26 – Hurricane Isaac
2013
No Named Storms – Frequent daily rain