Drivers of change in the relative abundance of dugongs in New Caledonia
C. Cleguer A B C F , C. Garrigue B C , M. M. P. B. Fuentes A D , Y. Everingham E , R. Hagihara A , M. Hamann A , C. Payri B and H. Marsh A
+ Author Affiliations
- Author Affiliations
A College of Science and Engineering, James Cook University, Townsville, Qld 4811, Australia.
B Unité Mixte de Recherche (UMR) ENTROPIE (Institut de Recherche pour le Développement, Université de La Réunion, Centre National de la Recherche Scientifique), Laboratoire d’excellence LabEx, CORAIL, Nouméa, BP A5, New Caledonia.
C Opération Cétacés, BP 12827, Nouméa, 98802, New Caledonia.
D Department of Earth, Ocean and Atmospheric Science, Florida State University, Tallahassee, FL 32306, USA.
E Centre for Tropical Environmental and Sustainability Science, James Cook University, Townsville, Qld 4811, Australia.
F Corresponding author. Email: christophe.cleguer@murdoch.edu.au
Wildlife Research 44(4) 365-376 https://doi.org/10.1071/WR16133
Submitted: 18 July 2016 Accepted: 30 May 2017 Published: 4 July 2017
Abstract
Context: Sound understanding of temporal changes in the abundance of wildlife species is required for assessing their status and for effective conservation and management. In New Caledonia, a single baseline aerial survey of dugongs in 2003 estimated a population of 2026 (± 553 s.e.) individuals. A second, similar survey in 2008 produced a lower estimate of 606 (± 200 s.e.) individuals, leading to concerns that the dugong population was experiencing a decline.
Aims: This study used data collected from additional aerial surveys with the aim of updating information on the current size of the dugong population in New Caledonia and investigating the drivers of change in the estimates.
Methods: Four additional surveys were conducted: one in each of the cool (June) and warm (November) seasons of 2011 and 2012 around the main Island of New Caledonia. Dugong relative abundance and density were calculated and compared among survey years and survey regions. Drivers of change in the dugong population size were then investigated.
Key results: The abundance estimates obtained from our four surveys ranged from 649 (± 195 s.e.) to 1227 (± 296 s.e.) dugongs. These new results were not significantly different to the 2008 estimate but were significantly lower than the 2003 estimate. There was no significant variation in the proportion of calves throughout the entire time series of surveys.
Conclusions: The dugong population of New Caledonia was relatively stable between 2008 and 2012. We could not find sufficient evidence to show whether the discrepancy between 2003 and the remainder of the time series is due to a real decline in the population or the result of the confounding effects of variation in environmental conditions, animal behaviour and sampling biases.
Implications: The stability of the dugong population between 2008 and 2012 is a positive outcome for local conservation and management of dugongs. This study also highlights the advisability of replicating baseline surveys to enable robust interpretation of temporal variation in population size estimates, and in turn, to improve the management of wildlife species.
Additional keywords: abundance, aerial survey, dugong, wildlife management.
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