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As we looked out over the salt marsh creek the rounded shape of a gray mud bank glistened in the early morning light: then it moved. At this point I could see it was a huge manatee. Not often are the native animals mistaken for geographical features but because of their size; up to fifteen feet long and nearly three thousand pounds; these slow moving aquatic mammals can sometimes be confused with the landscape. More often though, they are not seen at all as they lie just below the surface of the water and only bring their heads up momentarily to get a breath of air.
At first glance the head of a manatee has a likeness to that of a walrus, but that’s where the similarities end. These warm water herbivores are a class of animal more closely related to elephants than seals.
As one might suspect, manatees have big appetites and can consume between sixty to one hundred pounds of aquatic vegetation every day. Around Cumberland they feed mostly in salt marsh creeks where they find Spartina grasses and algae. Manatees can live in both fresh and salt water as long as it is above sixty-four degrees. However sixty-eight degree water will start them moving south to warmer areas in the winter; like the spring fed rivers in Florida where seventy-two degree water comes up from underground to create these waterways.
In the salty waters around Cumberland, manatees are attracted to any areas that have fresh water draining into them. Many times they will gather around docks while people are washing their boats to drink the fresh water run off.
In recent times boats have become a major problem for these large slow moving animals. Of course, manatees evolved in an environment without boats and few if any other threats from above. After man arrived though, things started to change. The early native Americans hunted them for food: spearing them from above the surface of the water. Naturalist and explorer, William Bartram, in the late 1700’s gave a vivid account of a native American manatee hunt in Florida. As Europeans took over the region, harvesting manatees for meat continued but with more sophisticated equipment, like harpoons and fire arms. But even with this relatively new form of predation, these surface dwelling animals managed to maintain a significant population. Now modern man has outlawed manatee hunting but also has brought with him that technological wonder, the powerboat. As a result: most all wild manatees today have prop scars and many have been killed by powerboats. When boaters approach a dock on Cumberland, the first signs they see are usually the ones that warn them to slow down for manatees In other areas, mostly in Florida, speed limits and refuges excluding boats have been established. Some of these areas are controversial and much has been written and debated about them especially in heavily developed locals where of course, there are large numbers of power boaters that want quick access to fishing areas and other water related activities. Fortunately, Georgia does not yet have the Coastal human density problems that are found in Florida so boat traffic is much lighter. In the future though; if this type of development should occur; especially with large marines that attract powerboats, the natural behavior patterns and physical well being of the manatees around Cumberland Island could be in jeopardy.
If you have never seen them before, the ghosts can be startling on the summer beach at night as they race across the illuminating beam from your flash light. After sunrise they are still there, but blend well with the beach and are often overlooked. If actively pursued though, they can move swiftly, changing directions instantly; and should these evasive actions not be enough; they can quickly disappear into a burrow already dug some where.
With a carapace of only two inches wide the ghost crab is well named and well adapted to its environment. Like other crabs with gills, the ghost must return to the sea to breathe, but they also have the ability to store enough oxygen in their bodies to spend most of their time on shore. Along with speed and amazing agility, ghost crabs have eyes on vertical stalks which allows for a 360 degree range of vision; also equipped with two strong claws the ghost crab is a formidable predator for an animal its size. On the beach and in the dunes of Cumberland Island they eat just about any type of small land or sea animal they can capture. However they are also scavengers and will feed on the decomposing bodies of larger animals. Ghost crabs are significant predators of baby sea turtles; they will often burrow into turtle nests and eat the eggs, but will also capture the hatchlings on the beach as they make their way from the nest to the sea. It’s not uncommon to see the remains of several baby turtles at the entrance to a ghost crab burrow. Of course there are larger predators about that will eat ghost crabs; sea gulls, raccoons and feral hogs will all make a meal of them. The crabs try to avoid these larger animals by digging burrows three to four feet deep. This works most of the time but a large hungry hog will dig them up and may excavate a huge hole in the process.
The beach on Cumberland Island attracts a lot of animals from both land and sea. This is a place where the life and death struggles of many species can be observed. During the warmer months the ghost crab is a major player in this drama. But as the weather turns cooler in the fall the ghost will disappear into its burrow where it becomes dormant for the winter. It doesn’t take long for wind blown sand to cover the entrance of a crab burrow and for at least half a year there are no signs of these animals at all. But when temperatures once again rise in the spring, the ghost will re-appear.
It is June and the terns have returned to Cumberland: two species in particular are most noticeable this time of year. The Least tern is only here during the summer and will nest on the Island. As their name implies, they are the smaller terns, only about nine inches long but feisty little birds that defend their nests against intruders. Least terns form loosely defined rookeries near both ends of the Island; being ground nesting birds they require broad areas of undisturbed high beach for this purpose. Many beaches located in the Least terns nesting range have been developed or otherwise impacted by man so suitable rookery sites and feeding areas are disappearing; making this fish eating bird an endangered species, and also making Cumberland’s beach a more valuable asset for their survival.
The much larger Royal tern is nearly a permanent fixture to Cumberland’s beach with a resident population in the area of almost year round. These elegant looking birds are also breeding this time of year but they do not nest on Cumberland: instead they will form large, dense and noisy rookeries on smaller islands or high sandbars where there are fewer nest raiding raccoons.
Cumberland’s beach however is a good place to observe the courtship process of both Least and Royal terns which can be a drawn out affair with a lot of posturing and body language. Finally when a male thinks he has a prospective mate he will present her with a fish; if she accepts the offer there is a good chance they will mate. Over the years though, I have seen a number of these guys standing around with dried out looking fish in there bills; apparently not all of the girls respond. To some this may sound more like a singles bar than a sandbar, but it is all part of the natural selection process where only one good tern deserves another.
May is when the sea turtles start nesting on Cumberland Island. At the end of the month, forty three nests had already been located. By the end of the summer there will be approximately two hundred nests on the beach if it is a normal year. These are loggerhead turtles that average two to three hundred pounds. They prefer the upper beach and foredunes as nesting sights; most of them will come ashore on the last hour of an incoming tide so they won’t have to crawl a long way to a suitable location; also, more turtles nest on moon lit nights when they can see the silhouette of the shorline.
Female turtles will dig a deep round hole with their back flippers and deposit anywhere from fifty to over one hundred and fifty eggs in the cavity. After covering the nest with sand the mother turtle returns to the sea and the eggs are left alone to hatch which takes about sixty days of incubation time. The sex of the young will be determined by the temperatures in the nest. For example: warmer nests in the high 80’s will produce mostly males.
Turtle nests are targets for predators. On Cumberland, raccoons, feral hogs and ghost crabs would all like to feed on the nutrient rich eggs. The National Park Service conducts a turtle research program that locates and covers nests with wire cages that will usually keep out raccoons and hogs. Crabs however are harder to guard against. After a nest hatches the baby turtles dig their way to the surfact and easily crawl through the protective wire cages to the open beach. Predation on young turtles from the beach to the open sea is heavy as they try to reach the large floating rafts of sargassum weed that can be hundreds of miles from shore in an area known as the Sargasso Sea. If a young turtle can make it that far it has a much better chance of survival as sargassum weed provides plenty of hiding areas from large predators. Once a sea turtle gains some size there is less chance of it becoming a meal for another sea animal. However, Loggerhead turtles develop slowly, at least they keep their close association with the protective Sargassum for up to ten or twelve years; it’s sometime between twenty and thirty years when Loggerheads become sexually mature. At this point in their lives they will return to the beaches where they were hatched; this time to nest themselves and repeat a process that has been occurring on wild beaches around the world for over 150 million years. In recent times though sea turtles have become threatened and endangered by man; a relative new comer with high impact on ocean eco-systems. Sea turtles now face a gauntlet of entanglement devices put into the sea by man such as nets and fish line. Plastic bags floating in the water also kill turtles as they mistake them for jellyfish; a favorite food source. Biological and chemical toxins from polluted waters have a damaging effect on turtles as well as other marine species.
Probably the single largest threat to sea turtles alone is the loss of suitable nesting habitat. These ancient reptiles evolved on wild undisturbed beaches; more and more of these areas now are becoming obstructed with human development; much of which is not compatible with sea tutle nesting activity. Cumberland Island however still has over seventeen miles of wild beach available to nesting turtles. This, along with help from the turtle research team is a positive development in favor of these endangered animals.
