6 June Turtle Exped

Download the full report here: June 2018 BIOT turtle expedition report (PDF)

Executive summary
This scientific expedition to Diego Garcia, British Indian Ocean Territory (BIOT) from 25 June to 18 July 2018 builds on previous conservation research on the ecology of hawksbill and green turtles in the archipelago. The primary objectives were to increase understanding of breeding green turtle movements within and outside of BIOT, to expand existing knowledge of the immature turtle population within the Diego Garcia lagoon, to update nesting population data via an island-wide beach survey and to continue monitoring of incubation conditions in BIOT.

1. A presentation on sea turtle conservation research in BIOT took place to a packed audience of about 100 military and civilian residents of Diego Garcia. Volunteers signed up for day- and night-time patrols to assist the science team with surveys of sea turtles.

2. Patrols of a 4 km beach section in south east Diego Garcia to survey nesting activities were carried out between sunset and sunrise for 9 consecutive nights. Scientists were assisted by 49 volunteers from all sectors of the community. Fastloc-GPS-Argos satellite tags were attached to 12 nesting green turtles bringing the total sample size of tracked turtles by the team from Diego Garcia to 35 nesting green turtles.

3. The long-term mark-recapture study of immature foraging turtles in Turtle Cove (commenced in 1996, and following on subsequent work conducted in 1999, 2006, and 2012) continued during the June-July 2018 visit. A total of 97 turtles (including 91 hawksbills and 6 green turtles) were tagged, measured, weighed and released back into the Cove. Of the 91 hawksbills, 23% had been tagged in previous years (some as early as 1996).

4. In order to study habitat use by immature turtles within the Diego Garcia lagoon, and whether individuals depart from BIOT to other distant sites, high resolution Fastloc-GPS-Argos satellite tags were used for the first time to assess their movements. During the expedition, 10 satellite tags were attached to eight hawksbill and two green turtles captured at Turtle Cove. Larger individuals (measuring over 50 cm curved carapace length) were selected for this study. The Sea Turtle Expedition Report: Diego Garcia, BIOT, June-July 2018 science team were assisted by 69 volunteers during nine days of survey at Turtle Cove.

5. Temperature loggers were deployed at two sites on the Index Site at a range of
turtle nesting depths and in shaded and unshaded beach zones. The data will be
recovered in 18 months.

6. Monitoring surveys of sea turtle nesting activities on the Diego Garcia index beach
and all along the 60 km outer coastline of Diego Garcia were conducted on 8 days
and assisted by 13 volunteers. Survey data will provide an updated assessment of
available nesting habitat, distribution of nesting activity along the perimeter of Diego
Garcia, estimated green turtle and hawksbill nesting numbers and patterns of

7. By the end of the expedition, initial satellite tracking locations showed that all of the
nesting green turtles remained just offshore of the nesting beach with haulout
locations indicating that individuals were returning to nest within the expected internesting interval of approximately 12 days. The immature turtles remain close to
Turtle Cove with some forays up the lagoon.

8. Ongoing sea turtle nesting surveys by the Natural and Cultural Resources Program
Manager (on Diego Garcia) and by the Senior Fisheries Patrol Officer (SFPO) (on
remote islands) were organised. Data files (six sites) were exchanged for the
ongoing Baited Remote Underwater Video (BRUV) study conducted by the SFPO
on the Great Chagos Bank.

9. Updates throughout the expedition were posted on Twitter (links to @BIOTscience)
and on the Facebook site Chagos Turtles. Membership has reached almost 200
followers and updates of sea turtle locations will be posted in the forthcoming