Emergence of Hatchlings

Hatchling sea turtles generally start to emerge at night from underground nests, then immediately crawl to the sea and then begin swimming towards open water. Not all the hatchlings of a nest travel to the surface at the same time. Most commonly, a large batch one night is followed by a smaller batch the following night. Some nests were recorded as producing small batches of young on as many as five different nights. Nests were excavated 7 to 10 days after hatching, because the climbing of hatchlings to the surface requires from 3 to 7 days after hatching (Quiescence of hatchlings). The period of quiescence results from the hatchlings being confined in a subterranean chamber where their carapaces are flattened. During this period, the yolks are resorbed and the muscles are prepared for a long swim. Alternatively quiescence may be obligatory when the oxygen demand of the emerging hatchling exceeds the rate of oxygen diffusion into the chamber. An inhibition of many activities by warmth might help explain why it takes turtles several days to reach the surface after hatching. Upon encountering temperatures much above about 30 ^oC., the hatchlings cease to avoid coming to the surface during the day. Hatchlings which reach the surface have a dampening effect on the activity of those below, because experimental removal of individuals at the surface led to activity within the nest and emergence of the turtle brood within minutes. Hendrickson (1958) has suggested that during the day heat inhibits activity and keeps the turtles below the surface until the cool of the night. A tropical beach often becomes extremely hot by day and there may be little or no shade available to the hatchlings; exposure to the intense heat of day could easily be fatal to them. There exists therefore a direct pressure for the development of thermal inhibition of activity. Emerging under cover of darkness also provides better protection from terrestrial and airborn predators. The longer the time to reach the sea the more chance predators have of making a catch. Daytime temperatures slow the hatchlings down, if they can not reach the sea; either they are caught by predators or killed under the sun. Upon emerging from the nest, the hatchling turtles risk encounters with numbers of predators on their way to the water. Foxes, dogs, jackals and ghost crabs are common predators of nests and hatchlings on the beaches of Turkey. Cages over nests can be used in order to avoid fox predation.

Sand extraction, vehicular pressure, beach erosion, litter, tar and oil, and high tides can all affect nest excavation, incubation, development of embryos and hatching. Most beaches in Turkey and Cyprus have on the high beach a conspicuous strip of oil and tar, carried by storms. Tar bars are also present under the surface of the sand. It has been suggested that turtles may mistake marine debris for edible items: plastic bags appear like jellyfish in the water, and jellyfish are more common in the diet of some marine turtles. That is why sublethal effects of debris ingestion have an unknown but probably negative effect on the demography of sea turtles.

Excessive rainfall and / or inundation can indirectly affect natural turtle nests by lowering the ambient sand temperature, thereby increasing the incubation period. Inundation can also harden upper sand layers, slowing the digging efforts of emerging sea turtle hatchlings.

Fishing nets, speed boats and lines cause trouble to adult turtles in the sea as they may become entangled and drown. In the whole Mediterranean, an estimated 50,000-100,000 mature and young turtles are caught each year on longline hooks and in nets set to catch fish. There is clearly a need for better data on fishing related mortality, especially concerning adults. In the absence of reliable data, it would be sensible to minimise risks especially to adult turtles, by restricting fishing close to known turtle feeding grounds, and nesting beaches.

Among the newer threats to turtles is the increasing incidence of fibropapilloma disease. Affected turtles exhibit large external tumours which may impair movement or grow across the eyes or mouth inhibiting feeding, breathing and vision. This disease is documented mainly in the green turtle in which it is common and is thus commonly known as "green turtle fibropapilloma disease" (GTFP).

^{Life cycle of Sea Turtles and Negative effects to the Population in the Mediterranean.}