Behavioural transition probabilities in dugongs change with habitat and predator presence: implications for sirenian conservation

2012 ◽  
Vol 63 (11) ◽  
pp. 1069 ◽  
Author(s):  
Aaron J. Wirsing ◽  
Michael R. Heithaus

Although not widely appreciated, prey can manage predation risk by modifying the sequence of their behavioural states. We explored this phenomenon in dugongs (Dugong dugon) subject to spatially and temporally variable risk of tiger shark (Galeocerdo cuvier) predation in Shark Bay, Australia. Dugong behaviour was assayed using focal follows and organised into sequences of foraging, resting, and travelling bouts. We used log-linear analysis to test for sequence differences in relation to habitat (deep, shallow) and predation danger (sharks present, largely absent). Dugongs modified their behavioural sequences between periods of high and low shark abundance: those at risk alternated more frequently between foraging, which constrains anti-predator vigilance, and travelling, which facilitates predator detection. Dugongs also avoided continuous series of resting bouts, during which awareness is reduced, when sharks were present. These changes were only observed in relatively dangerous shallow habitat, which is hunted disproportionately by tiger sharks; behavioural responses to sharks in deep habitat were modest. We conclude that dugongs in risky habitat resort to safer behavioural sequences in response to sharks. Given that human disturbance and predators are perceived similarly by many species, some forms of vessel interaction could compromise the fitness of sirenians by eliciting similar behavioural adjustment.

1988 ◽  
Vol 2 (4) ◽  
pp. 377-384 ◽  
Author(s):  
Mariko Miyajima ◽  
Noriaki Hamada ◽  
Etsuro Yoshimura ◽  
Akira Okubo ◽  
Sunao Yamazaki ◽  
...  

2021 ◽  
Author(s):  
Alice Manuzzi ◽  
Belen Jiménez-Mena ◽  
Romina Henriques ◽  
Bonnie J. Holmes ◽  
Julian Pepperell ◽  
...  

Abstract Over the last century, many populations of sharks have been reduced in numbers by overexploitation or attempts to mitigate human-shark interactions. Still, there is a general perception that populations of large ocean predators cover wide areas and therefore their diversity is less susceptible to local anthropogenic disturbance. Here we report retrospective genomic analyses of DNA using archived and contemporary samples of tiger shark (Galeocerdo cuvier) from eastern Australia. Using SNP loci, we documented a significant overall change in genetic composition of tiger sharks born over the last century. The change was most likely due to a shift over time in the relative contribution of two well differentiated, but hitherto cryptic populations. Our data strongly indicate a dramatic shift in relative contribution of the two populations to the overall tiger shark abundance of the east coast of Australia, possibly associated with differences in direct or indirect exploitation rates.


2022 ◽  
Author(s):  
Neil Hammerschlag ◽  
Laura H. McDonnell ◽  
Mitchell J. Rider ◽  
Garrett M. Street ◽  
Elliott L. Hazen ◽  
...  

2014 ◽  
Vol 161 (11) ◽  
pp. 2645-2658 ◽  
Author(s):  
Bonnie J. Holmes ◽  
Julian G. Pepperell ◽  
Shane P. Griffiths ◽  
Fabrice R. A. Jaine ◽  
Ian R. Tibbetts ◽  
...  

2017 ◽  
Vol 101 (3) ◽  
pp. 403-415 ◽  
Author(s):  
Alexandra C. Aines ◽  
John K. Carlson ◽  
Andre Boustany ◽  
Alyssa Mathers ◽  
Nancy E. Kohler

2006 ◽  
Vol 149 (4) ◽  
pp. 961-968 ◽  
Author(s):  
Aaron J. Wirsing ◽  
Michael R. Heithaus ◽  
Lawrence M. Dill

2008 ◽  
Vol 154 (3) ◽  
pp. 423-434 ◽  
Author(s):  
Jeff Kneebone ◽  
Lisa J. Natanson ◽  
Allen H. Andrews ◽  
W. Hunt Howell

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