The Numbers Are In!
The 2017 Season Adds Intrigue to the Nesting Trends
The 2017 Season Adds Intrigue to the Nesting Trends
Lawrence Wood, Ph.D.
Research Coordinator, National Save The Sea Turtle Foundation
Research Coordinator, National Save The Sea Turtle Foundation
Every year, the Florida Fish and Wildlife Conservation Commission (FWC) compiles the Statewide sea turtle nesting data that are collected by nearly three thousand environmental professionals, students, and volunteers from almost every Florida beach where sea turtles are known to nest. This virtual army of observers come from varied backgrounds and life experiences, but play a critical role in the management and recovery of Florida’s sea turtle populations.
Though five species of sea turtle are typically found in Florida’s waters, only loggerheads, greens, and leatherbacks nest regularly enough on Florida’s beaches to sustain meaningful reproductive populations. Amazingly, sea turtles are known to navigate to and reproduce in the same region their parents and grandparents (and so on) did, thus developing a multi-generational ‘lineage’ that can be very useful in making the link between nesting activity and actual population estimates. For example, genetic fingerprinting has revealed four distinct lineages of loggerhead turtles in Florida, one representing each of the four ‘corners’ of the State. Collectively, they represent the vast majority of the whole region’s nesting population, and as a result it is estimated that Florida’s beaches produce 90% of the loggerheads that reside in the entire North Atlantic basin.
But, there’s a catch...nesting effort is only a proxy for estimating changes in sea turtle populations over long periods of time for both obvious and not-so-obvious reasons. First, the obvious one is that only females emerge to nest, so that leaves all the males out of the count. Less obvious are the various quirks of sea turtle biology: any given female only nests every few years, and when she does, she may produce from 1-8 nests that season. So, for example, if you were to count 100 nests, you wouldn’t know if it was 100 turtles that nested once, 50 that nested twice, 25 that nested four times... and so on, you get the point; nor would you know what proportion of the total female population was in that year’s ‘cycle’ of nesters. Nonetheless, when nesting activity is carefully and consistently documented over long periods of time (decades), the data are the best available for identifying trends in either population decline or growth.
Good thing, then, that FWC started a network of careful and consistent nest counters back in the 1980’s, which continue to provide increasingly meaningful and interesting clues concerning the most common question asked of any sea turtle biologist... “How are the turtles doing?” Being a really hard question to answer quickly and easily, we often turn to our latest nesting ‘numbers’ to provide a quick and simple response like “good year” or “bad year”; but that unfortuntaly falls well short of the big picture. So, you ask, how ARE the turtles doing? To be honest, nobody can say for sure, but there are enough data to make two primary conclusions: first, loggerhead turtles (Florida’s ‘bread-and-butter’ species) seem to be maintaining fairly stable populations; and second, both green and leatherback turtles have demonstrated consistent and significant increases in nesting activity in Florida over the last 30 or so years. A cautionary note, however, even though 1988 seems like a while ago, the data barely cover one sea turtle generation.
Still, just as we become justifiably alarmed by declines in nesting activity (as we were in the early 2000’s), we are justifiably encouraged by the current trends. Florida’s coastal communities have, in large part, become accustomed to the annual arrival of the turtle season, and though big challenges remain, many have participated in programs intended to minimize their impact on the nesting habitat. Programs that reduce disruptive light pollution and predation are increasingly common, and beach/dune restoration projects are often choreographed to offset their activities with the nesting season. Thirty or so years of coordinated conservation efforts coupled with an ever-increasing number of sea turtle ‘fans’ in the State appears to be working, and its nice to know that there’s a relatively safe haven in the region for the continued reproductive success of these three species. Thanks and congratulations to the hundreds and hundreds of hard-working volunteers who have been out there every morning collecting these valuable data!
But, there’s a catch...nesting effort is only a proxy for estimating changes in sea turtle populations over long periods of time for both obvious and not-so-obvious reasons. First, the obvious one is that only females emerge to nest, so that leaves all the males out of the count. Less obvious are the various quirks of sea turtle biology: any given female only nests every few years, and when she does, she may produce from 1-8 nests that season. So, for example, if you were to count 100 nests, you wouldn’t know if it was 100 turtles that nested once, 50 that nested twice, 25 that nested four times... and so on, you get the point; nor would you know what proportion of the total female population was in that year’s ‘cycle’ of nesters. Nonetheless, when nesting activity is carefully and consistently documented over long periods of time (decades), the data are the best available for identifying trends in either population decline or growth.
Good thing, then, that FWC started a network of careful and consistent nest counters back in the 1980’s, which continue to provide increasingly meaningful and interesting clues concerning the most common question asked of any sea turtle biologist... “How are the turtles doing?” Being a really hard question to answer quickly and easily, we often turn to our latest nesting ‘numbers’ to provide a quick and simple response like “good year” or “bad year”; but that unfortuntaly falls well short of the big picture. So, you ask, how ARE the turtles doing? To be honest, nobody can say for sure, but there are enough data to make two primary conclusions: first, loggerhead turtles (Florida’s ‘bread-and-butter’ species) seem to be maintaining fairly stable populations; and second, both green and leatherback turtles have demonstrated consistent and significant increases in nesting activity in Florida over the last 30 or so years. A cautionary note, however, even though 1988 seems like a while ago, the data barely cover one sea turtle generation.
Still, just as we become justifiably alarmed by declines in nesting activity (as we were in the early 2000’s), we are justifiably encouraged by the current trends. Florida’s coastal communities have, in large part, become accustomed to the annual arrival of the turtle season, and though big challenges remain, many have participated in programs intended to minimize their impact on the nesting habitat. Programs that reduce disruptive light pollution and predation are increasingly common, and beach/dune restoration projects are often choreographed to offset their activities with the nesting season. Thirty or so years of coordinated conservation efforts coupled with an ever-increasing number of sea turtle ‘fans’ in the State appears to be working, and its nice to know that there’s a relatively safe haven in the region for the continued reproductive success of these three species. Thanks and congratulations to the hundreds and hundreds of hard-working volunteers who have been out there every morning collecting these valuable data!
Let’s take a look...
Loggerheads (Caretta caretta): Florida is a very important rookery for this species, often hosting 50,000+ nests per year. Though ‘down’ from 2016, last year’s count reinforces a fairly consistent 10-year pattern of bi-annual “highs and lows” in nesting activity, and may also reflect larger decadal trends that are just being revealed. Interestingly, though the numbers are relatively small, the Florida Panhandle has seen a strong reversal of a downward trend in nesting activity since 2010.
Leatherbacks (Dermochelys coriacea):
Florida has experienced a gradual increase in leatherback turtle nesting since 2000, reaching impressive highs (by Florida’s standards) between 2010 and 2015. The last three years have halted the impressive trend, however, making the next five years all the more important to determine if the recent increases can be sustained.
Greens (Chelonia mydas): Florida’s green turtle nesting trends have been nothing less than remarkable. In the year 2000, folks were impressed that there were, for the first time on record, more than five thousand nests in Florida. If you had bought stock in green turtle nesting then, you’d be happy with your returns;
last year just under forty thousand nests were tallied on the same amount of beach. There is, however, quite a fluctuation from year to year.For reasons still unknown, female green turtles have synchronized their nesting intervals in such a way that a dramatic bi-annual pattern of very active nesting seasons alternates with very low ones. The most intriguing aspect of the green turtle trend is where the future equilibrium may lie; the population can’t grow exponentially forever as competition between themselves and the other species that share the beach grows alongside. Either way, it looks like our Florida greens are mounting a strong and sustained comeback, which is great news for us all.
