The sea turtle rookery at Gnaraloo Bay, Western Australia: using nocturnal observations to validate diurnal track interpretations

Thomson, Jordan, Hajnoczky, Nora and Hattingh, Karen 2016, The sea turtle rookery at Gnaraloo Bay, Western Australia: using nocturnal observations to validate diurnal track interpretations, Chelonian conservation and biology, vol. 15, no. 2, pp. 187-196, doi: 10.2744/CCB-1219.1.

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Title The sea turtle rookery at Gnaraloo Bay, Western Australia: using nocturnal observations to validate diurnal track interpretations
Author(s) Thomson, JordanORCID iD for Thomson, Jordan
Hajnoczky, Nora
Hattingh, Karen
Journal name Chelonian conservation and biology
Volume number 15
Issue number 2
Start page 187
End page 196
Total pages 10
Publisher Chelonian Research Foundation
Place of publication Lunenberg, Mass.
Publication date 2016-12
ISSN 1071-8443
Keyword(s) Cape Farquhar
detection probability
Gnaraloo Turtle Conservation Program
green turtle
loggerhead turtle
Summary Critical gaps remain in our understanding of many sea turtle nesting aggregations inremote or undeveloped regions. Here, we summarize the first 8 yrs of systematic monitoring of therookery at Gnaraloo Bay, Western Australia. Diurnal track surveys on this approximately 7-kmmainland beach were conducted daily during nesting seasons 2008/09 to 2015/16. The totalnumber of emergences (i.e., nests and failed nesting attempts) recorded per season ranged from480 to 813 (mean = 679.0, SE = 49.1), whereas the number of nests ranged from 305 to 522(mean = 376.0, SE = 26.7). Peak nesting activity occurred between mid-December and lateJanuary, with approximately 70 emergences and 35 nests recorded on average per week duringthis time. The majority (97%) of emergences and nests were from loggerhead turtles (Carettacaretta), whereas the remainder (3%) were from green turtles (Chelonia mydas). The number ofloggerhead turtle emergences recorded per season declined significantly over the course of thestudy, wheras the number of nests did not, although we suspect that nest detection errorscontributed to the difference between trends. We conducted nocturnal surveys (i.e., directobservations) during parts of seasons 2010/11 to 2015/16 to validate diurnal track interpretationsand assess potential biases in the diurnal data set. Diurnal nest counts for loggerhead turtles wereunderestimates in all seasons but one, with an average nest detection bias of !13.0% (SE = 3.0).After accounting for this bias, we estimate that approximately 405 nests are dug by 85 femaleloggerhead turtles in the Gnaraloo Bay survey area annually. A similar or slightly lower amountof loggerhead turtle nesting activity occurs at the Cape Farquhar survey area, also located on theGnaraloo coast; thus, this region contains previously underreported nesting aggregations of thisspecies. The Gnaraloo rookeries may play an important role in the dynamics of the southeastIndian Ocean loggerhead turtle subpopulation and may still be depleted relative to historic levelsdue to historical predation by introduced foxes. Monitoring, research, and the protection ofGnaraloo beaches are, therefore, critical at this juncture.
Language eng
DOI 10.2744/CCB-1219.1
Field of Research 060201 Behavioural Ecology
050205 Environmental Management
05 Environmental Sciences
06 Biological Sciences
07 Agricultural And Veterinary Sciences
HERDC Research category C1.1 Refereed article in a scholarly journal
ERA Research output type C Journal article
Copyright notice ©2016, Chelonian Research Foundation
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Document type: Journal Article
Collection: School of Life and Environmental Sciences
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