HABITAT DESCRIPTION Beach Morphology: The beach can be divided into three major zones based upon the levels of low tide and high tide (Fig. 43). The area below low tide is subtidal, between low and high tide is the intertidal, and that above high tide is supratidal. Geologists often divide the beach into a backbeach area and the foreshore area, separated by the high tide line which may be marked by a change in sand texture and a wrack zone. The actual height of the high tide line varies throughout the tidal cycle and with meteorological conditions. Fig. 43 - Morphology of the Beaches showing different zones (modified after Rodriques and Shimizu, 1995). The backbeach and backshore areas are used by loggerhead sea turtles for nesting. We can categorize habitats in which nests are deposited in order to maximize our information about nesting. Because beaches are dynamic areas they can change rapidly and catastrophically for turtle nests. The boundary between the land and beach is usually marked by a spring high tide and/or storm scarp or a berm. Landward the beach may be backed by a bluff, a scarp, back beach dune ridges, dune field, marsh, or a washover fan. Active beach processes include movement of sand by water currents and waves resulting in erosion, deposition, or stasis. During storms this activity is dramatically enhanced resulting in rapid and significant movement of sand and the formation of erosional beach scarps, runnels, or deposition of sand. When such conditions occur on a high spring tide the scarp or dunes forming the boundary between land and the beach can rapidly change. At this time sand in suspension can be carried over the low areas behind the beach and result in washover fans or interdune swale flooding. The mobilized sand is sorted by density, size, and shape resulting in the deposition in the back beach deposits of interlaminated layers of quartz and heavy mineral sand (Fig. 44). The return to normal quiescent conditions slowly heal and obliterate these more dramatic effects. Figure 44 - Heavy mineral deposit on the Beach underlying loggerhead nest deposited in front of scarp. As wind blows across the beach, sand is picked up and carried in traction or suspension and dropped in wind shadows behind beach obstructions (Fig. 45). This normally results in a series of ephemeral back beach dunes being built on the boundary between the land and the beach. On areas backed by marshes or sand flats, there may be a berm-like sandy spit which is built by water and wind currents. These spits form a low, continuous dune-like deposit which slope gently onto the beach and onto the backbeach marsh or sand flat. Washover fans are commonly found in these areas and can be recognized by tongues of sand, often with inverted density stratigraphy, washed into the marsh and which often are bordered by rafts of wrack. Figure 45 - Dunes building in the wind shadows of vegetation on South Beach. You will try to categorize your description of nesting habitat in terms of this discussion. Describe the habitat selected in some detail. The parameters described will not cover all nesting habitats, so you will have to decide how much detail is necessary. Topography: One of the parameters that will affect the success of a nest is the height above normal sea level and relief around the nest. Although we are not 34
sure of what these parameters are nor how they affect nesting success, it seems prudent to attempt to measure them. This can be done by profiling to either the base of a storm scarp or to the last high tide level (and recording the date). This will allow us to evaluate nest success against elevation and flooding events. If nests are clearly in poor habitat [laid low on the back beach, laid in an interdune swale prone to flooding, or deposited adjacent to a permanent swale pond] they should be moved to better habitat nearby. (See section on Moving Nests). Erosion/Deposition/Inundation: Sea turtle nests laid on the back beach are in a dynamic system. After storms occur, it would be wise to immediately patrol your beach to assess damage to each nest, noting its condition in your notebook, and repairing level in which the nest chamber is exposed or within a few centimeters of the surface, loose sand may be shoveled to cover the nest and protect it from predators. If such a nest is low on the back beach, it may be inundated by several successive spring tides. Try to keep it covered and hope for hatching success. Stratigraphy: The stratigraphy of the beach depends upon what processes have been active in moving the sediment. The intertidal zone is characterized by quartz sands with ghosty laminations of heavy mineral sands and occasional scour and fill structure, ripple marks, and biogenic traces left by ghost shrimp and other organisms. The back beach is characterized by distinctly laminated alternating quartz and heavy mineral sands with occasional scour and fill structures and abundant biogenic burrow structures left by ghost crabs. Heavy mineral layers become more abundant and thicker as the back beach scarp is approached forming a condensed heavy mineral zone about 8-10 meters wide. In this zone heavy mineral sands may attain thicknesses of 15 to 20 cm. Because this sand is finer grained than the quartz sand, it seems to retain ground water in its porosity and may cause problems for incubation of eggs. This condition can be tested by taking a piston core several meters further along the beach. If you think eggs are deposited in a thick heavy mineral sand contact a colleague for a consultation. Vegetation: The identity and degree of vegetative cover for each nesting site ought to be recorded with the habitat description. NEST MONITORING General Information Figure 46 - Erosion of nest on north end of South Beach on 9/11 Nor-easter in 2006 [06-119]. any damage possible. If nests erode, screens have to be dropped to the surface and secondarily covered with small mesh raccoon squares (Fig. 46). If heavy wrack or sand covers the nest, it should be removed especially if there is danger of flooding by wrack dams or in interswale depressions. We would recommend cleaning down to the level of the screen or slightly above it. In the case of wrack, it should be completely removed from above the nest so emerging hatchlings will not be impeded. If erosion occurs to a When monitoring beaches for evidence of nesting sea turtle populations, the two most obvious things you should recognize are crawls and strandings. Crawls of course are easily denoted by their almost tractor tire track-like form evident in the sand above the lowest or most recent tide line. Crawlways: The presence of a crawl does not necessarily indicate that a nest cavity with eggs is present. A crawl without a nest having been deposited is referred to as a false crawl or, preferably a non-nesting crawl. The date, location, size, and a sketch of all crawlways, including non-nesting crawlways, should be recorded in your notebook and on the daily and weekly logs. Different species of sea turtles make different significantly appearing crawlways (Witherington, 1992). Size of the crawlway can be measured between the inner V s left 35
by the turtles claws. The direction of travel is indicated by the V s apex pointing backward on the crawlway (Fig. x). Information on date, location, and frequency of non-nesting crawlways is very valuable when assessing the affects of tide height, beach topography, presence of bright lights, and other factors that might affect when and where a female turtle might deposit her nest. The survey period for all beaches should span from mid-may through mid- August. If possible, all nests should be recorded, covered, and marked within a few hours after they have been deposited. Early morning surveys, before or after high tide, diminish the risk involved with moving nests imperiled by tides, erosion, or poor nest site selection. Erosional events such as strong northeasterly winds and/or strong storms can truncate or obliterate sediments containing nest cavities in a span of several hours, making them easy to overlook or misinterpret. Researchers must take care to avoid nesting shorebird areas often located just above the high tide line. Surveys should be scheduled so that vehicular traffic remains below the high tide line. Also, if possible, monitoring should continue until all hatching activity of nests has been recorded. Nest Validation: Remember, the presence of a crawlway, or even a nesting depression, does not always mean that a clutch of eggs is present. Crawlway Identification: Witherington has summarized the crawlways and sign of nesting for Florida sea turtles (Witherington, 1992). He has defined crawlway and nesting terms. We include these terms, or their synonyms in the glossary. The pattern different species of sea turtles make as they crawl across the beach are quite different and species specific. Sea turtle crawlways are typically bilaterally symmetrical across the center of the crawlway. Loggerhead crawlways are characterized by a distinctive offset of right and left flipper marks. The flipper marks are generated by an alternating use of left and right flippers in crawling which results in an offset pattern across the crawl way (Fig. 47). Crawlways of Green and Leatherback turtles are also bilaterally symmetrical and have individual flipper marks directly across from one another due to pushing simultaneously with both flippers during crawling. Leatherback crawlways often exhibit continuous tail drags while those of Green and Loggerhead turtles often exhibit more or less discrete push marks made by the tail. Turtles with injured flippers often produce asymmetrical crawl ways. An attempt to photographically document an identify individual turtles by their crawlways was made in 1992 on St. Catherines Island but not carried to completion due to time constraints. This technique was attempted again in 1993. Figure 47 - Crawlway of loggerhead sea turtle (from GaDNR). Table 7. Key to Common Sea Turtle Crawlway Identification a. Crawlway with alternating pattern of flipper marks = Loggerhead b. Crawlway with synchronous pattern of flipper marks, prominent tail push and drag: 1. Small size, about 1 m = Green 2. Large size, more 1.2 m = Leatherback Witherington (1992) set forth criteria to assess the probability of a nest being associated with sea turtle crawlways. He cited evidence of sand covering by 36
front flippers, including the production of a secondary body pit or scarping, sand flipped or misted over the entrance crawlway, and, for Leatherbacks, sand thrown in multiple directions. Slides observed of Leatherback crawlways indicate that they are immense and look a lot like a caterpillar tractor trackway. If you think you have a crawlway of a Green turtle or a Leatherback, please notify us immediately. Evidence of nesting often includes one or more of the following lines of evidence (Fig. 48): 1. An elliptical covering pit or nest-like area. 2, Thrown sand scattered across the beach. 3. Exit crawlway longer than entrance crawlway. The presence of a nest cavity must be validated for each and every suspected nest. Nest cavities are usually located at the topmost turning point or apex of a crawl (Figure 12C). A shallow, wallowed out area at the apex of a crawl usually indicates where a female has been actively digging a nest. Because of sand and beach conditions, Georgia turtles often wander along the dune or scarp face before nesting. Once finished nesting the turtle immediately returns to the ocean. The most probable location for the egg chamber is at the apex of the exit crawlway (Figure 12D). Egg chambers have an upside down lightbulb like shape with a narrow throat and a bulbous base. Dimensions of egg chambers will vary but they will usually have an average depth of about twenty five to thirty centimeters and a diameter of about twenty centimeters (Figure 8; 12E). Any sea turtle researcher must be familiar with basic egg chamber morphology so as to be better prepared when doing anything to a possibly viable nest. Digging and scraping are the best ways of validating a nest if positive evidence is found. However, these methods should only be used in cases where screening protection is needed, as on most Georgia beaches. Figure 48 - Nest of loggerhead sea turtle with short entrance crawlway to right, elliptical nest in foreground, and longer exit crawlway to left. Note raccoon tracks in foreground and thrown sand around covering pit. If digging or probing is required, there are certain guidelines that should be followed. Digging is the recommended protocol. The objective is to locate the bottom of the body pit dug by the turtle. This is done by carefully scraping the disturbed, bioturbated sand out of the body pit with a small shovel until the underlying firm, laminated sands of the beach are encountered. 37
nest can be detected by some predators up to four or five days after it was deposited. Because of this it is important to dig within several hours after the nest has been laid. At this point, opening the nest will not compromise its integrity because the scent is going to be detectable by predators for the next couple of days anyway. However, opening a nest cavity after the scent has dissipated would once again enable predators to locate it by smell and dig it up. Figure 49 - Egg chamber discontinuity showing bioturbated egg chamber fill as target bullseye against laminated beach sediments. Then this surface is very carefully scraped using a small trowel to attempt to locate the neck of the egg chamber by its circular discontinuity pattern where it penetrates the laminated patterned sands of the undisturbed beach (Fig. 49). Once the egg chamber neck is located, carefully dig into the soft sand filling its neck to confirm the presence of eggs. Backfill with loosely packed sand to the body chamber pit floor. Figure 50 - Searching for an egg chamber in a dune nest using a flat-edged sand shovel very carefully is not always a black and white situation. When probing is absolutely necessary, a long antennae-like tool is used by inserting it into the sand in an area where a nest cavity is thought to be located. As the probe is inserted and pushed into the sand it will normally hit the bottom of the body pit indicated by increased force to penetrate the sand beneath the body pit. When the probe enters the egg chamber neck, it will become noticeably easier to push the probe into the sand and to a depth obviously beneath the depth at which the bottom of the body pit is being encountered. This type of search method can be helpful in locating elusive nest cavities, but if the probe does enter an egg chamber there is always the strong chance of penetrating one or more eggs and destroying them. Also, the penetrated eggs can become a breeding ground for microbes and bacteria which could possibly destroy the whole nest. Thus, probing should only be used in cases where no other methods are applicable. If any eggs are broken during probing, they should be removed from the nest and disposed of in the ocean. When digging down into a freshly deposited nest remember to proceed with great care (Fig. 50). Only a small tunnel like opening is needed. The nest chamber is commonly situated in the center of the wallowed out area at the crawl apex. These signs will help pinpoint the location of the nest chamber. Also, keep in mind that when a female sea turtle covers up a nest that she has just deposited, she does not pack down the sand too tightly. The sand in the throat like tunnel leading down to the actual nest cavity must be just loose enough to allow the hatchlings to tunnel up and out through the slightly less compacted substrate. So, if digging is needed, think like a female sea turtle and remember to duplicate everything she would do when digging or covering up a nest cavity. Valuable insight into sea turtle behavior and nest morphology can be gained by going out at night and actually watching living turtles as they perform the arduous task of nesting. Digging by shovel or trowel is really the only sure way of positively validating the presence of a nest cavity, but painstaking care must be used to insure the integrity of the nest. The scent of a freshly laid LOCATING NESTS All nest site positions must be marked by the presence of a numbered and dated flagging stake. So 38
as not to reveal the exact location of the nest cavity on developed islands, all stakes may be placed in a predetermined position a couple of meters away from the nest proper. This prevents any unauthorized persons from tampering with a nest. On nonurbanized islands (Fig. 51), flagging and stakes are used for easy spotting of nest sites for research personnel so they can easily check for the daily status of all nests. Mapping Nest Location: The positioning of nests along the island beaches is a significant parameter of sea turtle nesting behavior. In order to accurately map the positions of all nests, it is necessary to tie the nest positions to a pre-surveyed beach grid or locate them by GPS. Beginning at the south end of the island, kilometer posts were erected in the dunes behind the beach every kilometer along the shoreline. Every hundred meters, between the kilometer markers, stake flags and fluorescent strip flagging was affixed to an easily seen tree, stump, or some other stationary object to mark intermediate grid points. Each nest location can be identified as to its position relative to the last designated kilometer station + the last designated 100 meter stake + however many meters it is from the last nest stake. All distances can be determined with the use of a hundred meter tape measure or a metric measuring wheel. All new nests can be marked with a stake and the crawlways erased daily so as to avoid duplicate counts on subsequent survey days. Also, all nest positions as related to surrounding dune topography can be accurately recorded. This information should indicate whether the nest is located on the berm of the beach or somewhere anterior, on top of, or posterior to the primary dune bedding. The use of GPS allows for more or less accurate mapping of nest positions (depending upon resolution), but is a more rapid technique. Be sure you have read the previous section pertaining to the use of the beach grid. Table 8. Checklist for Nest Documentation Location Nest Number Photo Frame Number(s) Measure Crawlway (total and between V s) Describe Crawlway Validate Egg Chamber Screen Nest Stake Nest Describe Habitat Position on Beach Beach background Beach Obstructions Document Predation Count Shells (Estimate %) Identify Predator(s) Describe Remediation Figure 51 - Proper conservation of a St. Catherines loggerhead nest involves screening, rebarring, and staking. NEST MOVING PROTOCOL Extreme care and caution should be exercised at all times when moving sea turtle nests and the proper procedures must be precisely adhered to. When to move a nest: All nests will be left in situ and only moved when imperiled by tidal inundation, erosion, deposition, or general poor nest site. Presence of large quantities of heavy minerals can also warrant the movement of a nest, and the decision to move a nest should preferably be made the morning after the nest was laid. This is because the eggs begin developing soon after deposition. If possible, discuss moving the nest with a colleague to reach a consensus. If still in doubt, call your supervisor to request a consultation. Moving Eggs: As always, be extremely careful when digging into a nest. [Think like a turtle!]. Nests can be moved (Fig. 52) within 12 hours of deposition and after 12 days. If moved within the first 12 hours, they should be handled gently and redeposited as rapidly as is possible. If relocated after 12 days, they need to be handled carefully and kept in their original orientation during the move. This can be done without marking on the shells. Procedure: 1. Remove all sand on top of nest cavity so all the topmost eggs can be clearly seen. 2. Place the eggs into a partly filled bucket of sand or cooler. [ After 12 days, The developing embryos are cradled in a permanent position at this point and must 39
not be turned upside down. Orienting the eggs upside down may prove fatal to the developing embryos. 3. Choose a new nest site above the highest high tide mark with a smooth slope down to the beach and little or no heavy minerals present in the subsurface. Also, try to choose a location within a hundred yards or so of the original spot, and with similar exposure to sunlight and/or shade. Amount of exposure to sunlight affects the average temperature within the nes,t which in turn affects the sex of the hatchlings. recorded and mapped as usual. Data concerning the old nest site should note reasons for moving the nest. PREDATION PROTECTION There are several methods that may be used when protecting sea turtle nests against possible predation, including screening, trapping, and extermination. Figure 53 - Have-a-Hart traps are a viable option to humanely capture small predators. Figure 52 - Relocation of a loggerhead sea turtle nest with eggs being counted into a ridid bucket with sand in its bottom. 4. Dig a new nest cavity and make sure the shape and dimensions are within acceptable parameters. 5. Now, pay special attention to orientation of the eggs as they are redeposited into the new nest cavity. The top of the eggs MUST remain on the top. Proper orientation plays a crucial role in further development of the eggs. 6. After the eggs have been properly oriented and redeposited, the remaining empty portion of the cavity and the throat-like tunnel leading down to it can now be filled in with sand. DO NOT pack in the sand too tight. The sand in the passageway leading down to the cavity must be just loose enough to allow the newly hatched young to tunnel up and out through the slightly less compacted substrate. 7. After everything has been properly covered, data on the new nest site and the old one should be Screening: This method involves securing sections of screen directly over nest cavities to prevent predators from digging down into the nest. The square sections should be secured at each corner with a rebar stake that has been driven into the sand. Only wire with openings in the screening large enough to allow the hatchlings to crawl through can be used [i.e. mesh sizes of 2 x 4 size]. If the openings are too small the hatchlings will be trapped or possibly injured as they attempt to pass through the openings. Sometimes a second screen with smaller mesh (1 x 2 ) is placed over the center of the egg chamber neck to keep raccoons from digging. When predation pressure is extreme, cages are often set on top of these screen to build a distance barrier between raccoons and the eggs. All screening should be removed if positive signs of nest emergence is evident. Positive sign of immanent emergence include the development of a slight depression abound the egg chamber. This will make it easier for any other hatchlings to dig out if a second emergence occurs the next night. Traps: In cases of predation involving raccoons (Procyon lotor) and/or pigs (Sus scrofa), live traps can be used (Fig. 53) to catch these animals and relocate them to areas where they will no longer pose a threat to nesting sea turtles. Always be extremely careful when dealing with any live animal, and 40
remember that raccoons can carry rabies. If a ghost crab burrows down into a nest cavity the scent of the breached cavity may once again be detectable by predators. Any incidence of this type can be taken care of by first removing the ghost crab from its burrow and then filling in the burrow with fresh sand a few feet away from the hole. 41