Welcoming the New Generation of Pacific Ridley Sea Turtle
Tara A. Spears
As twilight envelopes the beach giving much needed relief from the heat of the summer sun, only the whoosh of the receding waves can be heard. Through the deepening dusk a dark shape emerges from the sea, lumbering silently over the warm sand. Finally, when she senses she is above the high tide line, the sea turtle begins to gorge out a hole in the sand and lay her eggs.
This is the miracle of sea turtle nesting, one of the summer season’s greatest events. Along the Mexican Pacific coast near Jaltemba Bay, the most likely species is the Pacific Olive Ridley. It is the smallest of the sea turtles yet it has the most abundant population of any of the seven sea turtle species; sadly, all sea turtles throughout the world are classified as vulnerable (numbers decreasing) or endangered.
Witnessing the labor of these giant sea animals is so powerful, truly an experience that isn’t forgotten. After laying her eggs, the sea turtle appears to shed tears, but that is just the turtle secreting salt that accumulates in her body. Nonetheless, it is very emotional to watch.
Once all the eggs are in the chamber, the mother turtle uses her rear flippers to push sand over the top of the egg cavity. Gradually, she packs the sand down over the top and then begins using her front flippers to refill the body pit and disguise the nest. By throwing sand in all directions, it is much harder for predators to find the eggs. After the nest is thoroughly concealed, the female crawls back to the sea to rest before nesting again later that season or before beginning her migration back to her feeding ground. After leaving a nest, the female never returns to tend it.
Incubation typically takes about 60 days, but since the temperature of the sand governs the speed at which the embryos develop, the hatching period varies with conditions. Essentially, the hotter the sand surrounding the nest, the faster the embryos will develop. Cooler sand has a tendency to produce more males, with warmer sand producing a higher ratio of females. One would expect the recent hot summers to have produced more females.
While many people believe that a nesting sea turtle cannot be distracted from her task, this is not entirely true. I personally have witnessed times when a nest was dug and even a couple of eggs released, and a noisy bunch of people come running up to watch; the turtle aborted the process, returning to the sea instead of completing the birth. It is crucial to never disturb the nesting turtle with noise or sudden light. In areas monitored by conservation agencies, professionals will mark the nest site to help prevent human interference.
Sea turtles face many hazards in the water, including plastic pollution and accidental harm or death in encounters with commercial fishermen. According to sea turtle researcher, Pamela T. Plotkin (Texas A&M University), “Nesting season is an important opportunity for scientists to collect data on turtle abundance and trends.” To monitor population trends, scientists count the number of nests made on a beach during an entire nesting season. They estimate how many times an individual female turtle nests during one nesting season, and use simple arithmetic to calculate the estimated number of females that nested that year. Sea turtles typically nest every two, three or four years, so biologists need long-term data over multiple decades to track population trends.
According to some projections, by 2050 the oceans will contain more plastic than fish. Ocean plastic can kill marine animals when they are ensnared by it or ingest it in large quantities. Scientists have found many species feeding on ocean plastics, from fish living in the deepest ocean trenches to seabirds feeding at the surface. Since the early 1980s, turtle researchers have studied sea turtle diets and have found plastic in the stomachs and intestines of virtually all sea turtle species from the Gulf of Mexico to Pacific Ocean.
Overfishing also threatens sea turtles and other non-target animals, such as marine mammals and seabirds. Researchers believe that fishing pressure in the Pacific Ocean is the primary cause of a recent collapse of the leatherback sea turtle (Dermochelys coriacea) population in the eastern Pacific.
Climate change is triggering changes in ocean temperature, chemistry, circulation and sea levels. These shifts also threaten sea turtles, but there is little quantitative research so far on how significantly climate change will negatively affect any species.
Today, most coastal areas in North America protect beaches during nesting season. Government agencies, researchers and volunteers monitor many beaches and help hatchlings make it to the water. These measures have helped turtle populations increase. It would seem that the next urgent step needs to be reducing the use of plastic throwaway containers and eliminating the trash in the ocean.
For those who want to do something for turtle conservation in Riviera Nayarit, you can donate or volunteer with a group in San Pancho, Grupo Ecológico de la Costa Verde.
Within Mexico telephone: (311) 258-4100 From outside Mexico: 011-52 (311) 258-4100 or visit their website: www.project-tortuga.org