Relocating turtle nests: Why is this done? Is it justified? August 2009
By Bob Klotz
CEA Volunteers observing turtle nesting
One frequently asked question is why a nest should be moved.
Under ideal conditions, they should not be moved. Sadly, the presence of tourists or local visitors on the beach frequently leads to less than ideal conditions. In addition, preservation efforts are occasionally at odds with “natural” practices.
With respect to managing new marine turtle nests, standard practices recognized by the Mexican federal government offer four options to authorized tortugueros. In order of preference, these are:
(1)leaving the nests where they are;
(2) moving the eggs to an ostensibly safer position near the nesting site;
(3) moving the eggs to a protected area, called a “corral;” or
(4) moving the eggs to an artificial incubation facility.
Leaving the nests where they are is generally the optimal situation, since natural nests have a higher level of hatching success. When left in place, however, they do face some natural threats. If nests are deposited very close to the shoreline, as they frequently are, the eggs face the risk of over-saturation by seawater during high tides or storms, which leads to the drowning of the embryos. Many nests are naturally lost when sea turtles, especially Green Turtles (Chelonia mydas), lay their nests in “popular” nesting spots. In these cases, the eggs laid previously are left scattered on the surface, where the embryos die almost immediately. Some nests are subject to predation by local animals, including raccoons. And of course, many hatchlings are lost to predators as they make their way to the sea. Under ideal conditions—where there is absolutely no human presence—these are all natural, and ecologically sustainable losses. As is the occasional total destruction of all existing nests when a hurricane strikes. Obviously, none of these natural occurrences has deterred the survival of sea turtles over millions of years.
Human presence, however, adds a number of un-natural risks to nesting and to nests left in place. Depending upon the level of use by tourists and visitors, nests left where they are deposited are at risk for compaction. If compacted by foot traffic or mechanical compression by objects placed on the surface, the sand above the eggs—which lie between about 25 and 50 centimeters below the surface—can be pressed to the point of crushing the eggs. Or the sand itself can lose its natural porosity, limiting the flow of air and/or hindering or preventing the eventual escape of the hatchlings from the nest. Other risks include pollution of the nests by alcohol, sunscreens and other chemicals introduced accidentally into the sand; or by urine: both human, and that of dogs brought to the beach.
Unsupervised pets, especially dogs, also potentially pose a threat to the eggs, and then later, to newly emerging hatchlings.
Another risk to eggs left in natural nests is poachers. Although the collecting, selling and eating of marine turtle eggs—usually raw, for their supposed enhancement of men’s sexual performance—is a crime under federal law, the practice still persists. Unfortunately, most nesting beaches are not under federal surveillance. And the presence of tortugueros—and other observers of this illegal activity—only serves as a possible deterrent.
In heavily utilized areas, the generally accepted practice is to leave nests in place that are out of harm’s way, high on the dune. If a nest is believed to be at risk, it can be relocated to a more sheltered spot nearby as a second-best option—although any movement of the eggs usually leads to a drop in the survival rate.
The third alternative is to move eggs to a corral, a protected section of beach where there is no danger of trampling or poaching. This also results in a drop in survival rates, however.
The fourth option—moving eggs to an artificial incubation facility—is almost never practiced, because the cost is very high: both in terms of extremely poor survival rates—often as low as 0%—and the prohibitive operating and maintenance costs of such facilities.
Ultimately the decision to move nests to corrals, which is a common practice on heavily used public-access and hotel beaches, is driven by two factors: fear of loss of nests to tourist traffic and pollution, and pressure from environmental groups and the government to closely monitor and increase nesting and hatching results.
The managers of federally authorized marine turtle protection programs, including all of those administered by private hotels, constantly have to weigh the advantages of leaving nests in place against the losses of productivity. For example, while moving eggs to corrals almost always results in a partial loss of viability, hundreds of nests are potentially at risk each year to both human and natural causes. Even if the human risk is not taken into account, natural nesting behaviors portend the loss of many nests. Although Green turtles are late-season nesters that seem to prefer spots high on the dune, they and the Loggerheads (Caretta caretta) frequently deposit their eggs near the tide line—even as natural, seasonal beach erosion occurs toward late summer—making the nests more vulnerable to destruction by high and storm tides. Moreover, observation of nesting patterns reveals that certain sections of the beach are highly favored, leading to repeated nesting in the same spots. Moving just these nests in theory—although not yet scientifically confirmed—saves thousands of eggs and hatchlings, outweighing the losses due to the moving process itself. Under pressure from governmental and private monitors to promote high levels of hatching, managers may make “unnatural” decisions, opting for the safer, and more convenient, practice of moving eggs to corrals and monitoring more closely their progress.
Is moving marine turtle nests the “natural” thing to do? Absolutely not. Is it a better option for overall promotion of higher rates of survivability? On its face of it, this appears to be the case. But this needs to be investigated systematically at local beaches, taking into consideration the relative rates of turtle nesting and site selection on the one hand, and nesting beach utilization by tourists and local visitors on the other.
Bob Klotz is a resident of Aventuras Akumal, who works as a consultant to hotels and NGOs regarding environmental issues and environmental project development and monitoring. He has been trained as a tortuguero by Flora, Fauna y Cultura de México, A.C. and participates in daily beach inspections to evaluate the frequency and location of nesting sites.