Marine Creature: Hawksbill Turtle
Kindly compiled by Kate Walker of Vava’u Turtle Monitoring Program
Hawksbill Turtle – Eretmochelys imbricate. Can be distinguished from other marine turtle species by the sharp ‘hawk-like’ beak, the overlapped pointed or jagged scutes on the carapace and the four square prefrontal scutes between the eyes.
Food: Hawksbills diet mainly consist on sponges, their sharp beak being used to tear at sponges and reach into crevices in the reef.
Size: The average carapace length for a hawksbill turtle is 65-70cm but can reach up to 1m.
Distribution: Hawksbill sea turtles have a wide range, found predominantly in tropical reefs of the Indian, Pacific, and Atlantic oceans.
Lifespan: The life span of marine turtle species in general is unknown but estimates for hawksbills range from 30-50 years
All turtle hatchlings head out to the open ocean straight from hatching. These early pelagic years of all turtle species are known as the ‘lost years’ as very little is known about their life history, feeding, distribution or recruitment methods to tropical reefs.
The carapace (shell) of marine turtles is made from keratin, the same materials as our hair and nails. This material grows over the spine and between the ribs to form a solid shell which the spine and ribs are encased in.
Female hawksbills turtles breed every 2-3 years, migrating from their foraging grounds to beaches near to their original place of hatching. Upon reaching the breeding grounds, females will mate with multiple males storing their sperm within their body and fertilizing clutches of eggs internally. Once the eggs have developed enough to be laid, the female comes ashore (generally during the night), selects a nesting site towards the back of steep beaches amongst the vegetation, digs an egg chamber and lays between 80-140 eggs. She then covers the eggs and returns to the sea. Hawksbills nest approximately 4 times in each breeding season so once the female has returned to the sea, she will fertilise a new clutch of eggs with the stored sperm from her earlier mating and being the process again.
Feeding & Hunting
During their post-hatching pelagic years, juvenile hawksbills float in the ocean currents at the surface amongst Sargassum macro-algae patches. While much of this life stage is unknown, recent studies suggest that they are feeding on small marine animals that area also associated with these drift communities.
When hawksbills reach about 35cm in carapace length they switch to a coral reef associated life stage and recruit into the tropical reefs of nearby land masses. Once this switch occurs, hawksbills change their diet to sponge, with small quantities of algae and jellyfish also being consumed. When feeding on stinging jellyfish, hawksbills close their unprotected eyes which are the only part of their body susceptible to the venom.
As with all marine turtles, there are many anthropogenic threats to their survival. The IUCN Red List records the Hawksbill turtle as critically endangered and much of this decline is due to harvesting for the jewellery trade. The carapace of a hawksbill can be polished to reveal a beautiful mottled pattern which has been popular for decoration for over a hundred years.
In many small island nations there still exists a demand for turtle meat and eggs with legal and illegal harvesting of adults and their nests leading to declines in localised populations. Marine debris also causes much damage to the hawksbill turtle. Plastic bags in the ocean look very similar to jellyfish and are often ingested by Hawksbills leading to an obstructed gut and starvation. In addition to this, coastal development threatens the integrity and suitability of nesting beaches with artificial lights leading to disorientation of hatchlings and in some cases, coastal development leading to their erosion of the beaches.
There are also indirect threats to the survival of this species through climate change and rising sea levels. Hawksbills nest on fringing beaches of tropical islands, in the zone which will be most directly impacted with rising sea levels leading to a loss of nesting habitat. An additional potential threat to survival from climate changes is the associated rising temperatures. The sex ration of turtle nests are determined by temperature and with rising temperatures leading to hotter sand, there is a risk of a turtle population skewed towards females emerging leading to a lack of potential mates.
Conservation Status & International Protection
Hawksbill turtles are recorded as critically endangered on the IUCN Red List and this has led to their listing on the appendices of many international conventions:
- Convention on Migratory Species (CMS): Listed on appendix 1 and 2
- Convention on International Trade in Endangered Species (CITES): Prevents unregulated trade in listed species
- Specially Protected Areas and Wildlife (SPAW) program of the Cartagena Convention
- Inter-American Convention for the Protection and Conservation of Sea Turtles (IAC)
While all of these treaties and conventions do require a level of protection and conservation of marine turtles, they only apply to countries which have elected to ratify them. Countries who have chosen not to ratify are not internationally obliged to protect sea turtles in any way
How can people help?
Some simple steps that you can take to help protect hawksbill turtles:
Say no to any tortoise or turtle shell jewellery or decoration. If we can cut off the demand for these products then we can reduce the supply. In addition to this, the CITES convention is ratified by a very large number of countries and while it may be legal to buy turtle shell products within country, there are very few countries from which you can export it from or import it to.
Say no to plastic bags. If you are not using plastic bags then you can’t be responsible for your bag ending up in the ocean. Marine debris is a huge threat to many marine species and this simple step can help reduce the significant number of plastic bags finding their way into our oceans.
Report a sighting to a local NGO. For example if you see a turtle in Tonga you can contact Vava’u Turtle Monitoring Program
Best places in the world to see these creatures:
Hawksbill turtles can be seen on reefs throughout the tropical seas but are more commonly observed in the Caribbean and Gulf of Mexico region where their numbers are thought to be higher. There are many turtle conservation NGOs in this region, some are very well established and reputable such as St Eustatius National Parks Foundation (STENAPA), Sea Turtle Conservation Bonaire, St Maarten Nature Foundation, Tortuga Aruba and many others associated with the WIDECAST network.
If you are a marine operator here are some simple guidelines you should follow:
- Do not crowd or touch a turtle. Turtles breathe air and they regulate their breaths depending on their activity level. If you threaten or startle a turtle then they are liable to dive without taking the appropriate breaths and this can cause great stress and in extreme circumstances, drowning.
- Hawksbill turtles can be quite interactive in some part of the world. If you are quiet, still and non-threatening there is a chance that a curious hawksbill will come to check out your dive mask in very close quarters. In the Maldives, hawksbills are regularly observed climbing up a diver and staring them straight in the mask.
- Bring in any fishing lines when approaching reefs – you might hook a turtle.
Scientist Profile: Kate Walker
Description/Background of work
In Tonga there exists a demand for turtle meat as it is considered a delicacy to be served during cultural celebrations and harvesting is common during the open season. Live exports of turtles between island groups have been recorded, with most of these animals being sent for private and commercial sale/consumption. Turtle consumption was thought to be sustainable during past decades, however demand has increased, closed seasons are, reportedly, no longer being respected and traditional sustainable practices are being lost leading to a decline in the number of turtles in the local waters.The turtles of Vava’u have not been studied since 1974, and then only 4 of the smallest southern islands were investigated. Nesting was found on 3 of those 4 but no formal data has been collected since this time. One of the first things that we need to establish is where the turtles are nesting now and to do this we are working with communities and resorts on the outer islands to collect sighting data. With this data we are starting to build a picture of turtles in Vava’u as the baseline from where we start.
Importance of work
In specific regard to Vava’u, four main problems have been locally identified as the basis for establishing this conservation project. These are:
1. Illegal harvesting of nests and turtles during closed season
2. Lack of enforcement of legislation during the closed and open seasons on size limits, sex, etc
3. Lack of outreach to communities for protecting nesting and foraging grounds
4. Placement of static nets for fishing leading to turtle by-catch
The mission of this newly formed project is to address the loss of these traditional practices and to use proven community led models from Fiji and Vanuatu to develop capacity within communities environmental leaders with a focus on turtle conservation and education.
Web link: www.tongaturtles.weebly.com
Report a turtle sighting to Vava’u Turtle Monitoring Program
It is estimated that only 1 in 1000 hatchlings make it to breeding age so every single one is important for the conservation of this critically endangered species