Welcome to /r/science!
You may see more removed comments in this thread than you are used to seeing elsewhere on reddit. On /r/science we have [strict comment rules](https://www.reddit.com/r/science/wiki/rules#wiki_comment_rules
) designed to keep the discussion on topic and about the posted study and related research. This means that comments that attempt to confirm/deny the research with personal anecdotes, jokes, memes, or other off-topic or low-effort comments are likely to be removed (Yes, we all get that you want to be male sea turtles now).
Because it can be frustrating to type out a comment only to have it removed or to come to a thread looking for discussion and see lots of removed comments, please take time to review our comment rules before posting.
If you're looking for a place to have a more relaxed discussion of science-related breakthroughs and news, check out our sister subreddit /r/EverythingScience.
I study sea turtles. First, a minor clarification to the title - sex ratio is highly female-skewed *at certain beaches.*
It has always been the case that some beaches closer to the equator (warmer beaches) produce predominantly females, while other beaches farther from the equator, especially the “polar-most” beaches at the very fringe of the nesting range for certain species, produce mostly males. For instance in the US it has long been the case that southern Florida beaches produce mostly females while the North Carolina area produces most of the males (for loggerheads & greens).
What’s happening now is a sudden skew in ratios at both types of beaches, the mostly-female beaches going to all-female and the mostly-male beaches going to approx 50:50. The question is, can sea turtles alter nest depth or shift “polarward” to establish new male-producing nest sites, i.e. colonizing new beaches that haven’t been used before. Some recent studies have found that females at the “hot” beaches are indeed digging deeper (cooler) nests, apparently in a response to sand temperature, but that this is only partially effective (i.e. even the deep nests produce mostly females. Those deeper nests do produce a couple more males, but not enough to ensure optimum fertility of all females).
However, sea turtles are also shifting their range. For instance in the US, Assateague Island (Maryland) just had its first loggerhead nest, which produced 100 hatchlings, likely predominantly males. Kemp’s ridleys too are coming out of the Gulf of Mexico & starting to move up the eastern seaboard, and encouragingly Texas had a record number of Kemp’s nests last year (they usually nest in Mexico).
But a considerable problem here is that turtles are moving into areas that have not historically had them and that therefore don’t have basic protections set up to help nesting turtles. Cape Cod has been overwhelmed by a huge influx of young Kemp’s ridleys that end up stranded on the northern shore, in enormous numbers recently. Re nest habitat generally though, sandy beaches are usually intensely developed for human recreation and baby sea turtles don’t fare well with the “coastal roads + strip of houses + strong street lights” setup that we humans tend to put along most beaches.
This is one (of many) examples of species trying to shift their range in response to climate change, but in the process leaving the southern wildlife refuges & policies that had been set up to help them, and moving into more northern areas where no such protections yet exist. There is an interesting issue here of species moving faster than wildlife policy can keep up. (Same issue is occurring w N Atlantic right whales btw, which have just moved out of fisheries/shipping zones that were carefully arranged to not overlap w the whales, and into Canadian waters with no such regulations, the result being the worst die-off ever recorded, last summer. Ships smashing into them left & right, whales with horrific entanglements washing up dead. The Canadians have not had right whales up there before so it just took them all by surprise.)
Anyway, sea turtle survival may eventually depend on residents of mid-latitude beaches that have not historically had turtles being willing to rapidly change beach lighting/traffic policy to encourage sea turtle nesting. These mid-latitude beaches are the ones that can produce the males in the future. For example, US coastal residents in Maryland, Virginia & Long Island can help by watching for turtle nests & reducing lighting when nests occur. Though... the pace of change may become so rapid that we may need to move eggs, physically, to northern beaches so that those individual hatchlings will imprint on northern beaches. This is known as “assisted migration” and it may become essential, especially when the beaches themselves start moving/flooding as sea level really begins to change.
tl;dr - This is solvable if turtles can move to different nest sites, but we may need to help them move.
Oh I can see the puns and commentary about this already.
I'm sorry to sound ignorant but how is it that temperature determines sex? What is the science behind this?
And what does this mean, collectively, with such a wide ratio between female:male?
Would it mean that we could theoretically engineer an environment (lower sand temps) to increase the male population?