Document ID: chunk:federal_register_of_legislation:F2017L00641:body:0:p13
Version: federal_register_of_legislation:F2017L00641
Segment Type: other
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Character Range: 34806–37817

may not exhibit the same behaviours and have been observed nesting at locations up to 460 km apart within a season[108, 211]. The number of females nesting can fluctuate widely between years. In the case of green turtles this variation has been attributed to environmental conditions and food availability[143].

Eggs
For successful incubation, marine turtle eggs must be buried in ventilated, high humidity, sandy sites that are not subjected to flooding or erosion, and have a temperature range that persists within 25‑35⁰C for the duration of incubation[1, 109]. Marine turtles have temperature dependent sex determination. This means that the temperature during incubation determines the sex of hatchlings, with higher temperatures producing predominantly females[166]. There are also upper and lower temperature thresholds for successful incubation. The time frame for incubation differs across species, but is typically about two months. Adult turtles provide no parental care of eggs or young.

Figure 2. The generalised life cycle of marine turtles
 (adapted from Lanyon et al. (1989)[130]).

Hatchlings
Hatchlings emerge from the nest and orient towards the sea using the low elevation light horizon[258]. After entering the water, hatchlings use a combination of cues (wave direction, current, and magnetic fields) to orient themselves and travel into deeper offshore waters[150-152]. Crossing and swimming away from the beach is thought to imprint the hatchlings with the cues that allow individuals to return to their natal region for breeding as adults[153]. Hatchlings do not feed for the first few days of life relying on the remains of internalised yolk resources[257].

Pelagic juvenile
The life stage after a hatchling leaves its natal beach and swims offshore, until it returns to coastal waters some years later as a small juvenile, is referred to as the post-hatchling or pelagic juvenile stage. In general, hatchlings disperse into oceanic currents and gyres where they will stay in these pelagic environments until large enough to settle in coastal feeding habitats[21, 27, 257]. There is limited information on the distribution and biology of pelagic juvenile turtles for most species, with the exception of south-west Pacific loggerhead turtles. Loggerhead turtle pelagic juveniles in the south-west Pacific migrate from eastern Australian rookeries to South America and back[21]. Migrations are most likely made in conjunction with the predominant surface currents where young turtles can use the natural floating debris and biota that congregate along the current fronts to provide protection and food[257]. There is high natural mortality during this pelagic life stage. One exception to oceanic migrations by post-hatchlings is found in the flatback turtle, whose hatchlings are thought to spend this life phase within the continental shelf waters of Australia[136].
While in pelagic habitats, all species are primarily carnivorous, feeding on a range of macro-zooplankton[133]. The