June 16th 2018 is World Sea Turtle Day. Sea turtles are among the most majestic and charismatic marine animals and Love The Oceans doesn’t want to miss the opportunity to celebrate these beautiful creatures! In recognition of these awesome animals, this blog will be about sea turtles in Mozambique, their nesting ecology and LTO efforts to minimise disturbance.
Seven species of marine turtles exist around the globe. They are all grouped in the superfamily Chelonioidae. Six species, the Loggerhead, Green, Hawksbill, Olive Ridley, Kemp’s Ridley and Flatback turtle, belong to the family of Cheloniidae. The Leatherback turtle belongs to another family, the Dermochelyidae, of which it is the only living representative.
An overview of marine turtles and their conservation status:
- Leatherback (Dermochelys coriacea) – Vulnerable
- Green (Chelonia mydas) – Endangered
- Hawksbill (Eretmochelys imbricata) – Critically Endangered
- Loggerhead (Caretta caretta) – Vulnerable
- Kemp’s Ridley (Lepidochelys kempii) – Critically Endangered
- Olive Ridley (Lepidochelys olivacea) – Vulnerable
- Flatback (Natator depressus) – Data Deficient
Five species of turtles occur along the coast of Mozambique. Only the Kemp’s Ridley (restricted to the Gulf of Mexico and the Atlantic coast of the USA) and the Flatback (restricted to the tropical coastal waters of Australia) cannot be found in Mozambique waters. Two species even have a ‘local’ conservation status that is different from the global one. The South-West Indian Ocean subpopulation of Loggerheads is considered Near Threatened, a more favourable status compared to its global one, while the subpopulation of Leatherbacks is Critically Endangered in the South-West Indian Ocean.
All five species nest along the coast of Mozambique, but there is spatial variation in nesting behaviour, with certain areas favoured by certain species. Southern Mozambique is the preferred nesting area for Loggerheads and Leatherbacks. Guinjata Bay, the area where LTO operates, lies central in the depicted Loggerhead nesting range and close to the Northern limit of Leatherback nesting. Given the unfavourable conservation status of Leatherbacks in the area and their nesting range, it is, although possible, rather unlikely that nesting females or hatchlings will be observed in Guinjata Bay.
Adult turtles spend most of their lives in their foraging ground, an area usually separated and often miles away from mating and nesting areas. During the reproductive season, adult turtles travel to the nesting beach and both males and females can be found in the vicinity of this beach. Mating takes place along the migration route at courtship stations and in the area surrounding the nesting beach. Females usually nest more than once per reproductive season, but seldom in consecutive years.
Females construct their nest on a dry part of the beach, initially digging a body pit with her front flippers. Then, the rear flippers are used to dig the egg chamber. When the egg chamber is dug, the female is already in position and starts laying eggs. After depositing the eggs, the turtle again uses her rear flippers to cover the egg chamber after which she uses her front flippers to cover the body pit again and doing so disguising the nest.
Although the actual nesting is a similar event for each species of turtle, differences exist between species regarding egg size, clutch size, preferred beach type, incubation period, etc. Once a female turtle has laid a clutch of eggs, she leaves the beach and the eggs remain unprotected. There is also no maternal care for the hatchlings. Many natural factors threaten the survival of the incubating nest and hatchlings such as beach erosion, storm and tidal inundation and native predators. Devastating natural impacts are uncommon and not always predictable. However, there is a continuous threat of anthropogenic impacts on nesting beaches, nests and hatchlings that threaten the survival of all seven species of sea turtles around the world. Shore development, artificial lighting, beachfront structures, vehicle and foot traffic, sand compaction and pollution are all factors degrading nesting habitats globally. Nests and hatchlings are threatened by persistent poaching, predation by feral animals and pets, exotic pests, reduced chemical and physical sand quality for embryonic development, beach lighting and obstruction of hatchlings’ path towards the sea.
Even in rural areas such as Guinjata Bay there are threats to nesting turtles and hatchlings. LTO aims to minimise disturbance to turtles in Guinjata Bay by setting up guidelines for volunteers as well as running workshops with the local communities. Protocols for beach patrols during nesting season have been developed and our programs encompass these. The main goal is to secure the survival of turtles and hatchlings, while at the same time, collecting valuable baseline data on turtle presence, nesting and hatchlings in Guinjata Bay. Apart from the LTO’s general Don’t Touch, Don’t Tease, don’t Take policy with respect to any marine life, a few important guidelines have been developed to reduce disturbance to sea turtles, especially during nesting season. These guidelines are communicated to all our volunteers at the start of every program and LTO also spreads the word in the local community through presentations and posters. Some of the guidelines:
- Reduce number of outdoor lamps
- Shield or redirect outdoor lamps to reduce direct light on beach
- Close curtains or blindings during nesting season
- Use red light as much as possible
- Do regular beach cleans, especially bigger pieces of thrash can obstruct path of nesting females or hatchlings
- Don’t leave sun beds, chairs, tables etc out on the beach at night
- No driving on the beach, ESPECIALLY at night
- No fires on the beach during nesting season
Our July program is starting soon and even though nesting season is over, we will hopefully observe many turtles on our coral reef survey dives. We’ll keep you posted on our efforts and turtle encounters! Stay tuned and watch this space!