What I learned from Limpus, Carter. Quantifying a Nesting Season. and Hamann (2001) and. Sussing out. Identifying

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1 What I learned from Limpus, Carter and Hamann (2001) and Quantifying a Nesting Season Identifying Sussing out Michael Guinea School of Environment Charles Darwin University Darwin 0909

2 Whole of season monitoring Bramble Cay Track counts Nesting success Tagging of individuals Marking nests Hatching success

3 Figure 5 Nightly successful nesting and unsuccessful tracks

4 Figure 6 Cumulative arrivals and departures of nesters with available nesters at any time

5 Nesting Season at Scott Reef Location Sahul Shelf Previous reports Bob Prince early 1990s Kellie Pendoley early 1990s and 2000s Nesting numbers highly variable seasonality poorly defined Mick Guinea 1994, 2006, 2008, 2009, 2010, 2012

6 Sandy Islet, Scott Reef, Indian Ocean

7 Genetic Stocks of Australian Breeding Green Turtles : 1 = southern GBR; 2 = Coral Sea; 3 = northern GBR; 4 = Gulf of Carpentaria; 5 = Ashmore Reefs; 6 = Scott Reef; 7 = Northwest Shelf.8 = The Aru Islands Indonesian breeding stock (Dutton et al. 2002).

8 Sandy Islet (300 m x 70 m)

9 Sandy Islet Structures

10 Population of greens and hawksbills

11 Time Line of Green Turtle Tagging at Sandy Islet, Scott Reef Cumulative Number of Green Turtles tagged May- 90 Sep- 91 Jan- 93 Jun- 94 Oct- 95 Mar- 97 Jul- 98 Dec- 99 Apr- 01 Sep- 02 Jan- 04 May- 05 Oct- 06 Feb- 08 Jul- 09 Date Nov- 10 Number of Tagged Turtles

12 Surveys (WEL Surveys) Date Number of nights Time Ashore (hr) #Green Turtles tagged Feb Sep Nov Aug Sep- 3 0ct Dec Jan 1 Feb Jan 11 Feb 2010 Total Mean # of tracks /night ± sd 16.2 ± ± ± ± ± ± ± 5.43

13 Maximum information is gained by a 14 day survey in the middle of the nesting season When is the middle of the season? Which turtles are the new arrivals? ? Percentage Day of Nesting Season New Arrivals Departures Available Nesters Hatched Nests

14 Need to suss out the Nesting Season Cumulative Frequency Distributions Normal curve Sigmoid curve Logistic equation Which data sets are useful? How best to do it?

15 Solver (add in) Excel

16 Scott Reef Season Scott Reef 2008/ Jul-08 9-Sep Oct Dec-08 6-Feb Mar May-09 6-Jul-09 Date Cum Nest Logistic Predicted Values Cumulative Number of Nests

17 1/02/2009 8/02/ /01/ /01/ Track and Nest Data Scott Reef /09/ /09/ /09/2008 5/10/ /10/ /10/ /10/2008 2/11/2008 9/11/ /11/ /11/ /11/2008 7/12/ /12/ /12/ /12/2008 4/01/ /01/2009 Date Tracks + Nests Total Tracks 31/08/2008 7/09/ /08/2008 Number of tacks

18 Delambre Island, Pilbara, WA

19 Pronounced summer nesting Flatback population Delambre Nests 2010/ /09/2010 9/10/ /10/ /11/2010 8/12/ /12/ /01/2011 6/02/ /02/2011 Date Cum Nest Logistic Predicted Values Cumulative Number of Nests

20 Flatbacks Delambre Nests 2011/ /09/2011 4/10/ /10/ /11/2011 3/12/ /12/ /01/2012 1/02/ /02/2012 Date Cum Nest Logistic Predicted Values Cumulative Number of Nests

21 Bare Sand Island, NT

22 Protracted winter nesting population Bare Sand Island Apr May Jul-05 5-Sep Oct-05 Date Cum Nest Logistic Predicted Values Number of nests

23 Flatback (average nesting numbers) Bare Sand 2011 Nests Cumulative Numbers 26-Feb Apr-11 6-Jun Jul Sep-11 3-Nov Dec-11 Date observed turtles Logistic

24 Flatback (low nesting numbers) Bare Sand Island /04/ /04/ /05/ /05/ /06/ /07/ /07/ /08/ /09/20 12 Date Cum Nest Logistic Predicted Values Cumulative Number of Nests

25 Estimating the nesting population Number of nests per female per season Inter seasonal changes in internesting interval warm years vs cool years Intra seasonal changes in internesting interval early vs middle vs late in season Weather conditions warm calm seas = short interval (10 days) cool choppy seas = longer interval (21 days)

26 Is the logistic equation a useful descriptor of the nesting population? How much noise is in this metric? # Tracks > # nests > # turtles And what are we trying to measure? Is it the number of tracks? - crude metric Or number of nests? less crude metric Or number of turtles? better metric but difficult Or the contribution the nesting beach makes to the population i.e. nesting, hatching and emergence success?

27 My final 2 cents worth Change is inevitable! Keep on recording (record heaps) Be alert to changes Move off your patch once and a while If every nesting season was the same we would learn nothing new.

28 Thank You and thanks to The authors Col Limpus, Dave Carter and Mark Hamann, The late Daryl Riseley who left his delightful scribbles of the logistic equation on serviettes, table napkins, backs of envelopes and on my mind Volunteers, beach walkers, turtle whispers, and flatback fondlers of Bare Sand and Delambre Islands Rio Tinto Ltd Cape Lambert Woodside Energy Limited AusTurtle Inc