Presentation on theme: "00-014. Verifying the Presence of Eggs Once the egg chamber discontinuity is located by patient digging and scraping, the presence of eggs is confirmed."— Presentation transcript:
Verifying the Presence of Eggs Once the egg chamber discontinuity is located by patient digging and scraping, the presence of eggs is confirmed by gently digging into the neck of the egg chamber with fingers until eggs are seen. The sand is replaced to continue to protect the ping-pong sized eggs and the excavation back- filled. Loggerhead clutches on St. Catherines average 113 eggs per clutch. After validating the egg chamber, the position of the clutch is marked and the body pit is refilled to the level and contour of the beach surface.
Probing Problems Other methods of locating clutches of eggs are employed in other sea turtle programs. One of these, probing, is a technique using a rod or stick to gently probe the bottom of the nest to locate the typically softer sand of the egg chamber neck. Although effective, this technique has been found to be extremely hazardous as the eggs may easily be broken by probing too vigorously. This technique is used only as a last resort in our program and only by experienced personnel.
Screening to Protect from Predators Once the clutch is validated it is protected from predators by screening. A wire screen is placed directly over the egg chamber and held in place with steel stakes made from iron reinforcing rods called "rebar." This protects the eggs from being dug and eaten by raccoons or pigs. A second screen with a 1 x 2 mesh may be used on top of the flat screen. In areas liable to depredation we also place a Cumberland Cage over the other one or two screens. A painted stake is then marked with the nests number and placed near the screened nest.
Predation Management Management of predators involves l 1. Covering of nests l 2. Trapping l 3. Targeted Hunting
Relocating Nests Some areas of the beach are prone to be eroded or inundated by storm-driven tides. Some nests deposited during neap tides are deposited on the back beach in areas certain to be inundated by the higher spring tides. Such nests are moved to safer, nearby areas within twelve hours of their deposition. New egg chambers are dug to conform to the actual egg chamber, the eggs are carefully removed one or two at a time and cradled in a bucket on a cushion of sand, carefully transported to the nearest safe area, and redeposited one or two at a time, then covered as if an in situ nest.
Locating the Nest on Beach Grid The nest is then surveyed in onto a beach grid survey to locate the nest within a meter of its geographic position on St. Catherines Island. A beach grid can be established either by direct measurement with a 100m tape or measuring wheel or by geographic positioning system (GPS).
Notebook Documentation Data on the nests, its date of deposition, photographic documentation, geographic location, position of the beach, nature of the local habitat, and other unique aspects of the nest are then recorded in each scientists notebook. Other observations made during the days work are also entered to make a permanent record of each scientists activity each day. Data on nest dimensions and morphology was collected in 1994 to document relative size of egg chambers and nests to determine the chance of a randomly digging predator discovering the egg chamber.
Computerization of the Data The data taken in the field is transcribed onto a computerized data base and onto computerized data forms. These data can then be manipulated by computer to analyze patterns and attributes and to generate required reports. Daily work efforts, an up-to-date monitoring list, and cumulative nest data were recorded on a spreadsheet.
Conservation Research Each year we initiate a line of research to study and enhance the production of Loggerhead sea turtles on the Georgia coast. During 1993 and 1994 we monitored temperature of the sand above, within, and below nests, during 1994 we studied learned behavior in predators, during 1995 we studied the effects of ground water on nesting habitat, in 1996 we continued the ground water study and initiated a study of moving nests to small areas called "nurturies." Research is important because it allows us to experiment with techniques to enhance hatchling production to help conserve threatened Loggerhead sea turtles.
Daily Monitoring From the time the first nest is deposited on St. Catherines Island until the last nest hatches every nest is monitored every day, except at the very end of the season. Daily observations allow us to recover screens eroded by blowing winds, to exhume nests buried by blowing sand, and to expediently deal with predators who are learning depredation techniques too rapidly. Tracks of predators and other significant nest events are recorded as a code on daily monitoring lists which list all nests in location sequence on the beach.
Emergence of Baby Turtles After days, the eggs hatch and the hatchling turtles begin wiggling their way toward the surface. As they do, the sand falls below them and they work their way to a location just below the surface. In the dark of the evening, the hatchlings suddenly become active and emerge as a group onto the beach and scurry into the ocean. Once in the ocean they enter a swimming frenzy which lasts for many hours which assures that they become widely dispersed in the ocean. The large clutch size, night time emergence, and swimming frenzy are mechanisms which have evolved to assure survival of some individuals from the ravages of predation. Evidence of an emergence includes an emergence crater or hole and a myriad of small crawlways made as the turtles scamper to the sea.
Stoping After hatching the mass of baby sea turtles begin digging their way to the surface. As they dig upward, sand falls around and under them. This process, called stoping in the mining industry, allows the turtles to loosen sand above them and pack it in beneath them, forming a floored chamber, a stope. Occasionally a rain will occur as the baby turtles are stoping their way to the surface. When this happens, the sand becomes cohesive and does not easily fall from the ceiling, but forms an arch across the top of the nest. In extreme circumstances, this arch will not allow the sea turtles to touch the ceiling, stopping the stoping and exposing the turtles to death by drowning (if the rain continues) or by desiccation (if the conditions last too long). St. Catherines protocols mandate digging nests which are hatching and have been inundated by heavy rains (3" or more).
Hatchling The baby sea turtles are small 2-3 inch replicas of adults which often reach pounds and 3-4 feet in length at maturity. The baby sea turtles normally crawl across the beach at night enter the ocean and then enter an instinctive swimming frenzy for about 36 hours which acts as a dispersal mechanism to protect them from predators. Conservationists believe that 1 in 1,000 hatchlings may survive to reproductive age.
Real-World Experience! Three to five days after the last hatchlings emerge, each nest is carefully dug to find any hatchlings remaining in the egg chamber. Eggs are sorted into categories in stacks of 10 hatched eggs, unhatched eggs, and dead sea turtles to be counted. Whatever the condition of the eggs in the nest, it must be dug; leading to interesting sounds, smells, and sights.
Hands-On Science! Interns particularly enjoy finding live baby sea turtles remaining in the egg chamber. The babies are carried back to the Turtle House in insulated coolers to await release during the darkness of night by the interns and faculty. The St. Catherines Island Sea Turtle Conservation Program protocol calls for their release in as natural a way as is feasible; involving crawling across the beach, no artificial lights, and as little noise as is feasible.