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SWIOFP C5 - Satellite Tagging of Marine Turtles

Field Report

Compiled by Lindsey West, Sea Sense Coordinator

1. Study Site: Temeke District

Temeke District is the southernmost of three administrative municipalities in Dar es Salaam, the

commercial capital of Tanzania (Figure 1). Although the city is one of the fastest growing cities in sub-

saharan Africa, of the three municipalities, Temeke is the least populated (population of 768,541; National

Population and Housing Census, 2002) and is largely rural.

The majority of the 60km coastline is undeveloped with only a few, small scale tourist lodges. Beaches are

relatively pristine and are mostly bordered by coastal vegetation including coastal shrubs, Miombo

woodland, coastal swamps and mangrove forests.

Figure 1: Location of Temeke District, Tanzania

Temeke District

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2. Sea Turtle nesting activity in Temeke District

Nesting density is relatively low in Tanzania compared to other countries in the region. However, within

Tanzania, Temeke District is one of the most important nesting sites for green turtles (Chelonia mydas).

There are 13 known green turtle nesting beaches in Temeke District which total approximately 45 km

(Figure 2).

Figure 2: Location of green turtle nesting beaches in Temeke District

Green turtles nest all year round in Temeke District although there is a noticeable peak in nesting activity in

April and May. A nest monitoring programme was implemented towards the end of 2004. Since then

annual nest counts have ranged from 68 in 2005 to 147 in 2010 (Figure 3). The mean number of nests

recorded per year is 92 (SD±44).

Figure 3: Nesting activity in Temeke District, 2004 – 2011

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The most popular nesting site is near to Amani Gomvu village in central Temeke. There are two small

sections of beach totaling 5.5 km. Over a third (38%) of all nests recorded in Temeke District are laid on

these two beaches. Annual nest counts at this site range from 11 to 72 (between 2004 and 2011).

3. Sea turtle monitoring in Temeke District

In 2004, Sea Sense NGO established a community based sea turtle nest monitoring and protection

programme in Temeke District. Beach surveys were undertaken to identify potential nesting beaches and

interview surveys were conducted with local fishers to gain additional information about the status of sea

turtles in Temeke.

Seven key sites were identified and a number of Community Conservation Officers (CO’s) were

democratically elected by their communities to participate in the monitoring programme. A network of 12

CO’s now exists in Temeke District. All CO’s received training from Sea Sense in practical sea turtle

conservation techniques including nest identification, nest relocation protocols, monitoring of incubation

periods, nest excavations and data recording.

CO’s undertake daily foot patrols of nesting beaches in their vicinity. Upon locating a nest, the CO allocates

the nest an individual identification number and records important data including species, date of laying

and clutch size if relocated. Any nest under threat from poaching, predation by wild animals or tidal

inundation is moved to a safer area. Where the risk of predation from mongoose, monitor lizards and

honey badgers persists, nests are covered with a net which is removed prior to hatching. All nests are

monitored closely during the incubation period. Following hatching, the CO excavates each nest to assess

hatching success.

Data are submitted to the Sea Sense office on a monthly basis and entered into a nesting database.

4. Species targeted: Green turtles

Only two species of sea turtle (green and hawksbill) are known to nest in Tanzania. Green turtles are the

most common nesting species and represent 99% of all recorded nests in Tanzania.

5. Description of the protocol used to capture the turtle

In order to maximise the chances of intercepting a nesting sea turtle, patrolling effort was concentrated on

the two beaches near to Amani Gomvu village. Prior to deployment of the first tag, nesting data from

Amani Gomvu site were analysed and a specific turtle was identified for tagging. The date of her nesting

event was noted and using an average inter-nesting interval of 10 – 15 days, the expected date of the next

clutch was calculated. A team of three Sea Sense Conservation Officers were deployed to the field to

conduct nightly patrols of the nesting beaches during the 10 – 15 day period.

Due to the low nesting density in Temeke District, it is very rare that more than one turtle is encountered

on the same night. Therefore, it was considered likely that an encountered turtle would be the specific

turtle targeted for tagging. Upon encountering a nesting female, the team waited for egg deposition and

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nest covering to be completed and then applied a titanium flipper tag to each of the fore flippers (tag series

prefix TZ). This was counted as the second clutch.

10 days later the same team were deployed to the field to intercept the same turtle a second time. This

was counted as the third clutch. Once the tag number was confirmed and egg deposition was verified, the

satellite tagging team were contacted and joined the patrol team for attachment of the satellite tag.

After completion of the nesting event, the turtle was captured and a wooden box was placed around her.

The box was dug into the sand to prevent the turtle escaping. The GPS location of the capture point was

recorded. The curved carapace length (CCL) and curved carapace width (CCW) were measured and two

tissues samples were taken from the posterior flippers (one left and one right) for genetic analysis.

Capturing the turtle Collection of tissue samples

The same procedure was used for deployment of a second satellite tag. However due to logistical

constraints, the third satellite tag was deployed on a nesting turtle that had not been intercepted on any

previous occasion. However, analysis of nesting data suggested that she had already laid two clutches.

6. Description of the protocol used to attach the satellite tags

The carapace of the turtle was sanded and cleaned with acetone in preparation for attachment of the

satellite tag. The bottom and sides of the tag were also sanded and cleaned and the wet/dry sensors

covered with tape for protection.

The epoxy resin was mixed and a small amount applied to the cleaned area of the carapace. Further resin

was applied to the base of the tag and the tag was then placed in position on the second central scute.

The position of the tag was checked and adjusted to ensure alignment with the head of the turtle. The

remaining epoxy resin was applied to all sides of the tag and shaped into a hydrodynamic mould as much as

possible. The tape was removed from the wet/dry sensors and the epoxy was left to set for 5-6 hours.

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Attachment and positioning of the satellite tag

Tag position: rear view Tag position: from left side

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Tag position: from right side

Tag position: dorsal view

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Tagged turtle returns to the sea

7. Summary table

Molly Lulu Rosie

Site name Ras Kutani

(Mindadi beach)

Kimbiji

(Mlonge beach)

Amani Gomvu

(Mfuguni Beach)

GPS coordinates S06.93056

E39.50278

S06.97000

E39.52026

S06.95139

E39.51139

Date 29/03/2012 05/05/2012 22/07/2012

Species Chelonia mydas Chelonia mydas Chelonia mydas

Behaviour Nesting Nesting Nesting

Size CCL : 104cm

CCW: 94cm

CCL : 102cm

CCW: 92cm

CCL : 109cm

CCW: 102cm

Metallic tag number TZ049 (lt) TZ059 (rt) TZ066 (rt)

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TZ060 (lt) TZ067 (lt)

Satellite tag series

Number

647925 657917 647918

Satellite tracking ID

number

112304 112302 112303

Transmission

duration

26 days 36 days 24 days

Genetic sampling

number

(Posterior flippers)

TZ049 (Lt) 29/03/12

TZ049 (Rt) 29/03/12

TZ059/TZ060

05/05/12

Lt and Rt

TZ066/TZ060

21/07/12

Lt and Rt

Observation

8. Results

All three tagged turtles remained in Tanzania. Two of the turtles went on to lay further nests after tagging.

Therefore the tags provided valuable data on behaviour during the inter-nesting interval and identified the

location of an important foraging ground for gravid females. Both utilized a reef known as Sukuti in

Mkuranga District. Sukuti reef is approximately 6km wide and 7km long and is located within 30km of the

nesting beaches where both turtles were tagged. Both individuals showed high site fidelity, returning to

the reef during each of their inter-nesting intervals. Unfortunately both tags stopped transmitting after 26

and 36 days respectively at which point neither turtle had commenced a post nesting migration.

The third turtle commenced a post nesting migration soon after tagging and traveled north to Pemba Island

(Figure 4) where she continued to forage. Her tag stopped transmitting after 24 days so it was not possible

to determine how long she remained at this location.

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Figure 4: Satellite tracks of migrating turtle, August 2012

9. Discussion

The SWIOFP sea turtle satellite tracking project is the first of its kind in Tanzania and has provided

invaluable data on inter-nesting behaviour and the location of important foraging grounds for gravid

females. As a result of the satellite tracking, the first ever migratory corridor for a green turtle with natal

origins in Tanzania has been identified. However, the transmission durations were very disappointing, most

likely due to the use of Telonics tags which are poorer quality than the recommended Wildlife Computer

tags that have been widely used in previous studies in the region.

Green turtles nesting in other parts of the Western Indian Ocean (eg; Mayotte, Glorieuses Island) have also

been tracked along the Tanzanian and Kenyan coasts, indicating that the East African coast is an important

migratory corridor. This highlights the importance of the work being done at a regional level to identify

high risk areas for migrating sea turtles in the Western Indian Ocean. Furthermore, the presence of an

important migratory corridor along the East African coast supports the need for a region wide sea turtle

conservation strategy.

10. Acknowledgements

Sea Sense is grateful for the financial support provided by SWIOFP to conduct this project. Thanks also to

Sea Sense Conservation Officers for their patrolling efforts and assistance in deploying the tags.