Sex, Depth, and Temperature: An Analysis of Sea Turtle Nesting Temperature by Depth and the Use of Fabricated Eggs on the Upper Texas Coast

Abstract

Sea turtles exhibit temperature dependent sex determination where higher temperatures produce a greater number of female hatchlings. This leaves them vulnerable to climate change where an increase global temperatures can skew their populations sex ratios towards female potentially leading them to collapse. Sea turtles already face many anthropogenic and natural threats including habitat destruction, incidental fisheries bycatch, nest predation, tidal inundation and plastic pollution. With six of the seven extant species listed as endangered in at least one of their distinct population segments (DSP) any added strain to these species could be detrimental. Currently all sea turtle nests on the Upper Texas coast are excavated and sent to an incubation facility at Padre Island National Seashore (PAIS) on North Padre Island, Texas where they are kept until they hatch and are released. This study was conducted to provide a base line of the nesting temperatures of the three most common sea turtle species on the Upper Texas coast to test the hypothesis that temperatures are elevated in this region. We also set out to determine if the use of fabricated sea turtle eggs is beneficial in temperature studies involving sea turtle nest and the effect of nest depth on temperature. Here we show that the temperature in nests is significantly impacted by depth and the presence of fabricated eggs. We found that mean temperatures in nest with fabricated eggs was significantly lower (27.7℃) than those without (27.82℃). Mean temperatures at 25cm and 42 cm were lower when fabricated eggs were present while nests at 80 cm were higher indicating depth was the more important variable on temperature. During the data collection period there were three tidal inundation events that lowered mean temperatures of all nests and could potentially have been lethal to any real sea turtle nest present. Overall, we determined the use of fabricated eggs in future studies is unnecessary, and any nest left in-situ on the Upper Texas coast have a high probability of mortality.