Loggerhead turtle
Common name: Loggerhead turtle
Scientific name: Caretta caretta
Conservation status: The loggerhead turtle is 'Endangered' in Queensland (Nature Conservation Act 1992) and 'Endangered' nationally (Environment Protection and Biodiversity Conservation Act 1999).
Description: The loggerhead turtle is dark brown above, sometimes irregularly speckled with darker brown. The top of the head is dark brown, becoming pale on the sides with irregular darker blotches and white, cream or yellowish below. Hatchlings are rich reddish-brown above, dark blackish-brown below. The head of old adults is large. The shell is somewhat elongate and more or less heart-shaped with five costal scales on each side of the carapace (shell). Its head and body length can reach 1.5m. The identification key (PDF, 328K)* shows how to differentiate between loggerheads and other marine turtles.
Adult loggerhead turtle. Photo: C. Limpus (DERM)
Habitat and distribution:
The loggerhead turtle has a worldwide distribution in coastal tropical and subtropical waters. In Australia, loggerheads occur in coral reefs, bays and estuaries in tropical and warm temperate waters off the coast of Queensland, Northern Territory, Western Australia and New South Wales.
Behaviour and life history:
Loggerheads will travel vast distances from their nesting beaches. Females originally tagged near the south-east Queensland rookeries have been recaptured in Indonesia, Papua New Guinea, the Solomon Islands, New Caledonia, the Northern Territory, New South Wales and other parts of Queensland. Loggerheads tagged in Western Australia have been recaptured in the Northern Territory, Western Australia and Indonesia and Queensland.
In Queensland, loggerheads nest on the southern Great Barrier Reef and adjacent mainland coastal areas, including Bundaberg, Wreck Island, Erskine Island, Tryon Island, Wreck Rock beach and Pryce Cay. In south-eastern Queensland, mating starts about late October, reaching a peak in December and finish nesting in late February or early March. About 125 ping-pong ball sized, round parchment-shelled eggs are laid. Hatchlings emerge from the nests from late December until about April with most emerging from February to early March.
Loggerhead turtle recovery:
In Queensland the loggerhead turtle population is showing signs of recovery because a high proportion of loggerhead nests occur within national parks, and because Queensland Government staff have worked hard to declare marine protected areas and develop sound fisheries regulations to reduce by-catch.
Since the compulsory introduction of turtle excluder devices into trawl fisheries of northern Australia and eastern Queensland in 2000, the significant decline in loggerhead turtle nesting numbers in eastern Australia has ceased. Eight years later, we are seeing the beginnings of a population recovery. These successes in marine species conservation are a direct result of long-term commitment by the Queensland Government to strong species conservation, strong habitat protection, and management for sustainable fisheries.
At Mon Repos Conservation Park, DERM staff protect turtle nests during the nesting season, carry out research and monitoring, and raise public awareness through guided tours where visitors can have the unique experience of watching turtles lay their eggs.
In order to reduce the impacts of trawler fishermen on all marine turtles, the Queensland Government has initiated a rebate scheme until 2010 to help fishermen start using more effective bycatch reduction devices on their nets. These devices include turtle exclusion devices (TEDs), which are a grid of bars at the neck of a trawl net that catches turtles and allows them to escape through an opening at the top or bottom of the net.
Hatchling. Photo: Kate Winter.
Threatening processes:
Although the loggerhead turtle population is showing signs of recovery, they are still threatened by light pollution, boat strike, feral predators, and crab pots.
- Light pollution: Lights from coastal development results in changed light horizons, which causes increased mortality of hatchlings when they move towards stronger light sources inland instead of the low horizon out at sea. There is also a decline in the recruitment of new adults to nesting populations on lit beaches as they avoid brightly illuminated beaches.
- Boat strike: Boat strike can kill loggerhead turtles especially in estuaries, sandy straits and shallow inshore areas, and damage increases with boat speed. Damage to the shell may lead to death or disruption to feeding or breeding regime.
- Feral predators: Feral predators, such as foxes, eat loggerhead turtle eggs and hatchlings. Although the Department of Environment and Resource Management (DERM) are controlling feral predators on islands and mainland sites where loggerheads nest, the control of feral predators are still an ongoing issue as they continue to invade from adjacent habitat.
- Crab pots: Loggerhead turtles get tangled and drown in commercial and recreational crab pots and their float lines. Trap types that cause an impact include round crab pots, collapsible pots, and spanner crab traps.
Recovery actions:
- Increase public awareness about the effect of light sources around nesting sites and promote the use of alternative lighting and protection of nesting sites to local councils through the ‘Cut the Glow to help Turtles Go’ campaign;
- Encourage boat users to ‘Go Slow for those Below’ and slow their boat speed in estuaries, sandy straights and shallow inshore areas;
- Maintain the work by DERM staff to control feral predators on nesting islands, and encourage landholders near the coastline to control feral predators on their land; and
- Support the existing work by the Queensland Government who is working with the fishing industry to develop turtle-friendly crab-pots.
What can be done to help this species?
To help this species you can:
- If you live within 5km of beaches in south Queensland, support the ‘Cut the Glow to help Turtles Go’ campaign by turning off all non-essential lighting during the summer turtle breeding season;
- Decrease your boat speed in estuaries, sandy straights and shallow inshore areas, and remember to ‘Go Slow for those Below’;
- If you are a property owner within 10km of south Queensland beaches, remove feral animals such as foxes, dogs and cats from your land to prevent them eating the eggs of loggerhead turtles;
- Remember that rubbish you throw away can find its way to the sea, where turtles can mistake things such as plastic bags for jellyfish. Plastic swallowed by mistake can cause blockages of the stomach and intestines of marine animals such as turtles; and
- If you live adjacent to beaches in south Queensland, join your local Community Turtle Monitoring group and assist in protection and monitoring of turtle nests. For more information contact michelle.jones@derm.qld.gov.au
Further information:
A Biological Review of Australian Marine Turtles: 1. Loggerhead turtle Caretta caretta (Linnaeus)
A number of Queensland Turtle Conservation Project studies at different islands can be downloaded from DERM’s Caring for Wildlife web-page
Turtle and dugong ‘Go Slow’ areas in Moreton Bay Marine Park
Environment Australia and Marine Turtle Recovery Team. 2003 . Recovery plan for marine turtles in Australia. Department of the Environment and Heritage, Canberra.
Spotila, J.R. 2004. Sea turtles. The John Hopkins University Press, London.
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Last updated: 03 September 2009