One Size Does Not Fit All for South African Turtles
By Ronel Nel , George Hughes , and Jenn Tucek
The tell-tale notchings on an adult turtle’s shell decades after she received them. © Mariuns De Jager;
In the summer of 1963, the first conservation officers set foot on the beaches of Maputaland, northern KwaZulu-Natal, South Africa, where they discovered two species of nesting sea turtles, as well as an active turtle harvest under way in local communities. It was quickly determined that direct intervention was necessary to ensure that these species would be around in the future, and that while researchers actively pursued protection on the ground, it would be possible to simultaneously accomplish important research and monitoring goals. Today, after nearly five decades of patrolling the South African coastline, we researchers have now learned a good deal more about these turtles and how to conserve them.
“Over 30 years’ time, about 350,000 loggerhead hatchlings were “tagged” by having marginal scutes removed in a particular pattern that corresponded to the year in which they entered the ocean.”
During those first few years, conservation patrols were initiated to protect and document all nesting loggerhead and leatherback females that came ashore. Conservation officers still walk and drive along the beaches to count, measure, and tag all turtles encountered. Indeed, one of the keys to South Africa’s sea turtle conservation success has been the long-term commitment to continuous monitoring. Moreover, efforts are run from within a committed and stable government body—the Natal Parks Board, now Ezemvelo KZN Wildlife—and through longstanding partnerships with WWF–South Africa and others.
In the early seasons, much of the activities were based on trial and error. Turtles were turned on their backs so as not to escape as officers continued their patrols, returning later to tag them with cattle or sheep tags. Attempts were even made to use shark tags! Over time, it became clear that such tags were inappropriate for turtles, as was turning them over on their backs, but where we researchers did get it right was to be clear in our objectives from early on. For instance, we collectively maintained that harvesting needed to stop while populations were in recovery, but it could be considered again in the future should the turtle populations reach a threshold size.
If we were to measure population growth over the years, monitoring needed to be consistent and quantitative. It is with some pleasure that we can now say that nesting loggerhead numbers have increased threefold since conservation efforts began more than 40 years ago. On the one hand, although the threshold of 500 nesting females per annum has been reached, the issue of resuming the harvest of loggerheads has not surfaced again because the interest of the community has since shifted to sustainable tourism.
On the other hand, leatherbacks started—and remain—at low numbers (fewer than 100 females nesting per annum). The question is why two species that have received absolutely equal protection have not recovered at the same rate. Because there is no indication that offshore threats are specifically targeting leatherbacks, we suspect that conditions on the beach, such as the influence of nest temperatures on leatherback sex ratios, are hampering recovery. With leatherback numbers in South Africa still low and with other global leatherback populations in a perilous state, our local population merits continued care. We are investigating this disparity between species in hopes of replicating our loggerhead success with leatherbacks.
The Natal Parks Board staff displayed particularly good foresight by initiating mutilation tagging of hatchlings in 1970 to eventually be able to estimate age to maturity, one of the most important yet elusive biological traits of sea turtles. Over 30 years’ time, about 350,000 loggerhead hatchlings were “tagged” by having marginal scutes removed in a particular pattern that corresponded to the year in which they entered the ocean. The only similar program for loggerheads exists in Mon Repos, Australia, under Colin Limpus’s leadership. Today, 15 to 30 years after these programs were begun, some peoples’ heads have greyed and other people have retired, yet adult loggerheads bearing telltale notches in their carapaces are returning to their natal shores in substantial numbers to nest for the first time. Using these tagging codes and a bit of tricky statistics, researchers are able to estimate the ages of first-time nesters. It seems that females reach maturity at about 20 years (or a shell length of 84 centimeters [33 inches]), but age at reproductive maturity does vary broadly (10 to 35 years). We expect to refine these results in the near future as more data become available.
Combining these two experiences—monitoring efforts and notching experiments—we can offer some lessons learned. To begin, one must have clear objectives for a monitoring program from the start! Flipper tagging in isolation is not research, conservation, or monitoring; although counting nesting females is fundamental, additional information is necessary to evaluate the success of conservation and monitoring. Next, if monitoring, research, or conservation protocols work, don’t change them! And just because a protocol works for one population does not mean that it will work for all populations. Each country, each population, and each rookery is unique in its challenges. One should use the local strengths, which are often found in individual champions, to make conservation work. Most important, we have learned from the slow and steady turtles that slow and steady really is a good strategy for long-term success in conservation as well.
Government researchers in KwaZulu-Natal, South Africa, have been using a unique tagging system to mark hatchling loggerhead turtles since 1970. Hatchlings are marked by removing marginal scutes in a specific pattern that corresponds to their year of hatching. If the turtles return to nest as adults, scientists are able to determine their age—an otherwise impossible task. © Stephen Nash / CI adapted from George Hughes
This article originally appeared in SWOT Report, vol. 6 (2011). Click here to download the entire article as a PDF.