October marks the start of the nesting season, which means that from anytime now onwards along the sandy beaches of Mozambique we can expect to see nesting female turtles arriving to lay their eggs.
In the evenings and all through the night, adult females, haul themselves ashore. Females will return to their natal beaches, or the region of the coast where they were born. An amazing navigational feat, as they migrate back to a beach they spent only a few minutes on during the hatching process, some 20 or more years later. The most common species to nest along the shores here in Southern Mozambique are the Loggerhead and Leatherback.
During the nesting season Oct- Feb the turtles will lay multiple clutches of eggs approximately every 16 days. The loggerhead commonly lays 100 or so ping pong ball sized eggs into a cylindrical nest with a bulbous chamber at the bottom. The eggs will incubate over the following 5-8 weeks, their developmental rate controlled by the environmental temperature. During the middle third of the incubation period the developing embryos are highly sensitive to environmental temperatures (i.e. the beach sand) which determines their sex. Warmer temperatures >29.5 degrees C will produce females and <29 will produce males. Its around 29.5 degrees C that a combination of both sexes can be produced, a temperature known as the pivotal temperature.
As the nesting season continues, females will hang around in coastal waters adjacent to the nesting grounds, while the next set of eggs develop in their oviducts. During this time the females may forage for food and have been known to selectively feed on certain types of calcareous algae to help them gain the nutrient necessary to produce the eggshells.
Remember during the nesting season, females coming ashore to lay and emerging hatchlings are highly sensitive to artificial light, particularly the brighter white, blue and purple end of the spectrum. Once ashore on the nesting beach the turtles use the brightest source of light and horizon level, to orientate themselves towards to ocean, which in a natural environment is usually the moon or stars reflecting off the ocean. If an artificial light source is present, this will always appear brighter than the moon and stars, and thus the turtles will directly crawl towards these sources. To prevent stress on the animals and disorienting them landwards rather than sea wards, switch off any unnecessary lights or switch light globes those with a red colour, as the turtles eyes are not as sensitive to this colour.
If you see any nesting turtles or their tracks in Mozambique please contact Jess: