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False killer whale (Pseudorca crassidens) sightings in continental shelf habitat off Gabon and Côte d'Ivoire (Africa)

Published online by Cambridge University Press:  29 May 2013

Caroline R. Weir ,
Tim Collins ,
Terry Cross ,
Alison Gill ,
Simon Elwen ,
Michael Unwin  and
Richard J. Parnell
Caroline R. Weir*
Affiliation:
Ketos Ecology, 4 Compton Road, Kingsbridge, Devon, TQ7 2BP, UK Department of Zoology, School of Biological Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen, AB24 2TZ, UK
Tim Collins
Affiliation:
Wildlife Conservation Society, Ocean Giants Program, Global Conservation, 2300 Southern Boulevard, Bronx, NY 10460, USA Environment Society of Oman, PO Box 3955, PC 112, Ruwi, Sultanate of Oman
Terry Cross
Affiliation:
c/o Ketos Ecology, 4 Compton Road, Kingsbridge, Devon, TQ7 2BP, UK
Alison Gill
Affiliation:
c/o Ketos Ecology, 4 Compton Road, Kingsbridge, Devon, TQ7 2BP, UK
Simon Elwen
Affiliation:
Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria
Michael Unwin
Affiliation:
c/o Ketos Ecology, 4 Compton Road, Kingsbridge, Devon, TQ7 2BP, UK
Richard J. Parnell
Affiliation:
c/o Agence Nationale des Parcs Nationaux (ANPN), Batterie 4, BP 30 379, Libreville, Gabon
*
Correspondence should be addressed to: C.R. Weir, Ketos Ecology, 4 Compton Road, Kingsbridge, Devon, TQ7 2BP, UK email: Caroline.Weir@ketosecology.co.uk
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Abstract

The false killer whale Pseudorca crassidens is currently documented from only six eastern tropical Atlantic (ETA) range states, five of which are evidenced by strandings, by-catch or skeletal remains rather than at-sea sightings and consequently provide no information on habitat or behaviour. Here we report six false killer whale records from cetacean surveys carried out off Gabon (four records) and Côte d'Ivoire (two records) between 2002 and 2012, providing the first at-sea sightings in those two existing range states. All six sightings were located in continental shelf waters (≤103 m depth) and in relatively nearshore (mean = 13.9 km) habitat. Forty-three false killer whales were photo-identified during three encounters on the Gabonese shelf; seven individuals were matched between 2002 and 2006, including two individuals that were present during all three sightings. Observations included predation of Atlantic sailfish Istiophoms albicans and two occurrences in proximity to humpback whales Megaptera novaeangliae. Whistles recorded during one sighting had simple structure, short duration and a mean fundamental frequency of 7.8 kHz. These are the first verified records of false killer whales using continental shelf waters in the ETA, indicating that the species occupies neritic habitat in the region in addition to its previously-documented oceanic habitat. The re-sightings of marked individuals between sightings and years suggest that at least some individuals exhibit a degree of site fidelity to Gabonese shelf waters. Further information on distribution, abundance, movements, population structure and mortality rates are required for effective management of the species in the ETA.

Keywords

Gulf of Guineadistribution rangephoto-identificationvocalizationsdietsite fidelitywater depthcontinental shelfhabitatmarine debris
Type
Research Article
Information
Marine Biodiversity Records , Volume 6 , 2013 , e65
Copyright
Copyright © Marine Biological Association of the United Kingdom 2013 

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Footnotes

7

Present address: Iziko South African Museum, 25 Queen Victoria Street, Cape Town, 8000, South Africa

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