Sea Turtle Populations Turning Female?
December 15, 2018
The number of threats against sea turtles keeps on increasing as climate change progresses. Climate change is causing currents to change, sea levels to rise, and air and water temperature to increase. Rising temperatures are affecting the sex ratios in juvenile hatchlings which is causing the number of sea turtles to decline.
Unlike mammals, when the gender of the offspring is determined by what chromosome the father passes on, sea turtles use temperature dependent gender determination (NOAA). Temperature-dependent gender determination is when the deciding factor for the gender of the offspring is based off the temperature that the eggs are kept in. In order for a hatchling to be female, the temperature of the egg must be hotter than 85℉ and anything cooler than 85℉ makes the hatchling male. With climate change causing the air temperature to increase the female sea turtle population is increasing and the male population is decreasing. The journal of Current Biology did a study on the sea turtle populations on Raine Island.
It was found that 99.1% of the juveniles, 99.8% of subadults, and 86.8% of adults were female (Smithsonian). A juvenile is a turtle that is not full size, strength, or sexually mature.
A subadult is very similar to a juvenile but, they are approaching sexual maturity (WIDECAST). Current Biology also took surveys of the sand temperature and they found “analysis suggests sand temps have been climbing since the 1960s”(Smithsonian).
It is obvious that the male sea turtle population is suffering, but both male and females are finding ways around the small male populations. One of the things that males are able to do when breeding is to breed with multiple females during a single breeding season. Females can also breed with multiple males and then fertilize multiple clutches of eggs (Conservation Magazine).
Sea turtles don’t reach adulthood until 10 to 15 years after hatching. Scientists David Owens stated, “We won’t see the effects of what’s happening today for several decades” in an interview with The New York Times. The fact that scientists are aware of the decline in males in turtle populations now allows them more time to find a solution for the population ratio problems.