Common name: loggerhead turtle
Scientific name: Caretta caretta
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 elongated 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 Queensland Marine Turtle Field Guide shows how to differentiate between loggerhead turtles and other marine turtles.
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.
Life history and behaviour
Loggerhead turtles 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. Nesting finishes 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.
Hatchlings from Queensland disperse as far as South America, spending around 16 years at sea before returning to the south-west Pacific.
Diet: Loggerhead turtles are carnivorous, feeding mostly on shellfish, crabs, sea urchins and jellyfish. They appear to forage in deeper water (Cogger 1994).
Loggerhead turtle recovery
Despite the fact that more than 80% of nesting occurs within protected areas in Australia, the loggerhead turtle population in the early stages of decline for the south-west Pacific stock though stable in Western Australia. There has been a marked reduction in the number of turtles recruiting to Australian foraging grounds following the long oceanic phase, which could be due to fisheries bycatch or marine debris entanglement. Since the compulsory introduction of turtle excluder devices into trawl fisheries of northern Australia and eastern Queensland in 2000, there has been a rebound in nesting turtle abundance. Fox control measures have also increased hatchling production.
At Mon Repos Conservation Park, 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.
Major threats to loggerhead turtle populations include climate change, marine debris -entanglement and ingestion, chemical and terrestrial discharge, light pollution and fisheries bycatch. Other threats include feral animal predation, habitat modification and boat strike.
- Climate change impacts appear to be affecting nesting sand temperatures with changes in hatchling sex ratios and emergence success and increased extreme weather events resulting in erosion of nesting sites.
- 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.
- 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.
- Invest in climate change research and monitoring programs to assist adaptive management of likely climate change impacts.
- Reduce the impacts from marine debris through improved source reduction, collection and management.
- Minimise chemical and terrestrial discharge through best practice industrial, urban and agricultural run-off and stormwater management.
- 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.
- Maintain feral predators control programs on nesting islands, and encourage landholders near the coastline to control feral predators on their land.
- Support the fishing industry to develop turtle-friendly crab-pots.
What can you do 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, control 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.
- 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 firstname.lastname@example.org.
- Marine wildlife strandings
- Boat strike impact on turtle and dugong in Moreton Bay
- Queensland Parks and Wildlife Service 2016. Queensland Marine Turtle Field Guide . Department of National Parks, Sport and Racing, Brisbane.
- Commonwealth of Australia 2017. Recovery plan for marine turtles in Australia. Department of the Environment and Energy, Canberra.
- Turtle and dugong ‘go slow’ areas in Moreton Bay Marine Park
- Turtle watching
Cogger, HG 1994. Reptiles and Amphibians of Australia. Fifth Edition. Reed Books, Chatswood, NSW.