Monitoring of tracks on nesting beaches is required to establish a baseline of how many turtles there are and to detect changes into the future. Monitoring will provide more information on the North West Shelf flatback population as well as increasing understanding of the conservation status of the species. Monitoring the North West Shelf population over time will also inform conservation managers whether the Gorgon Project is having a significant effect on the North West Shelf flatbacks.
Chevron monitor the turtle nesting beaches on Barrow Island and those nesting on the mainland at Mundabullangana Station. DBCA established two additional sites for monitoring flatbacks – at Thevenard Island and Delambre Island (in partnership with Rio Tinto). These sites are all within the same breeding population of flatbacks known as the North West Shelf flatbacks. DBCA also collects monitoring data from reference sites in partnership with local, community groups to compare neighbouring flatback populations with the trends in population of the North West Shelf flatback population. These sites are Karratha, Port Hedland, 80-Mile Beach, Eco Beach, Cable Beach and Cape Domett.
Most monitoring occurs at nesting sites, as we can predict where and when the turtles will be there. It is also easier to find and approach turtles when they are on land. Beaches have marked, patrolled sections that are patrolled at the same time of year each year. Two main techniques can be used:
Morning after surveys
These surveys involve walking the designated beaches first thing in the morning to record:
- the total number of crawl tracks per species and a GPS location for each one
- the number of successful nests per species and a GPS location for each one
- the number and location of disturbed nests
- potential causes of nest disturbance
- presence of predators
- the number of hatched nests
Capture-mark-recapture survey techniques
These surveys involve walking sections of beach whilst turtles are nesting (usually overnight) to record:
- the number and position of turtles, which species, and whether they successfully lay a nest
- tagged turtle sightings
Additional survey techniques involve:
- applying flipper tags and PIT tags on nesting females (to identify them when re-encountered)
- measuring nesting females
- collection of skin biopsies on nesting females
- deployment of satellite tags/ loggers on nesting females
- excavating nests
- taking egg or hatchling measurements
- counting eggs per clutch
- recording clutches per season
- recording intervals between clutches
Some key indicators are compared, such as the annual nesting abundance (how many nests each year); nesting success (whether the female successfully lays eggs when she comes up on to the beach); hatching success (how many of the eggs laid hatch) and emergence success (how many hatched turtles successfully leave the nest chamber). Other environmental factors may also be recorded such as sand temperature.
Monitoring locations map
Click on the locations below for more information about each monitoring site.