Occurrence of false killer whales (Pseudorca crassidens) and their association with common bottlenose dolphins (Tursiops truncatus) off northeastern New Zealand |
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Authors: | Jochen R Zaeschmar Ingrid N Visser Dagmar Fertl Sarah L Dwyer Anna M Meissner Joanne Halliday Jo Berghan David Donnelly Karen A Stockin |
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Institution: | 1. Coastal‐Marine Research Group, Institute of Natural and Mathematical Sciences, Massey University, , North Shore, Auckland 0745, New Zealand;2. Orca Research Trust, , Tutukaka 0153, New Zealand;3. Ziphius EcoServices, , Plano, Texas 75025, U.S.A;4. , Opua 0200, Bay of Islands, New Zealand;5. , Kerikeri 0230, Bay of Islands, New Zealand;6. Australian Marine Ecology, , Kensington, Victoria 3031, Australia |
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Abstract: | On a global scale, false killer whales (Pseudorca crassidens) remain one of the lesser‐known delphinids. The occurrence, site fidelity, association patterns, and presence/absence of foraging in waters off northeastern New Zealand are examined from records collected between 1995 and 2012. The species was rarely encountered; however, of the 61 distinctive, photo‐identified individuals, 88.5% were resighted, with resightings up to 7 yr after initial identification, and movements as far as 650 km documented. Group sizes ranged from 20 to ca. 150. Results indicate that all individuals are linked in a single social network. Most observations were recorded in shallow (<100 m) nearshore waters. Occurrence in these continental shelf waters is likely seasonal, coinciding with the shoreward flooding of a warm current. During 91.5% of encounters, close interspecific associations with common bottlenose dolphins (Tursiops truncatus) were observed. Photo‐identification reveals repeat inter‐ and intraspecific associations among individuals with 34.2% of common bottlenose dolphins resighted together with false killer whales over 1,832 d. While foraging was observed during 39.5% of mixed‐species encounters, results suggest that social and antipredatory factors may also play a role in the formation of these mixed‐species groups. |
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Keywords: | false killer whale
Pseudorca crassidens
bottlenose dolphin
Tursiops truncatus
mixed‐species groups interspecific associations photo‐identification foraging seasonality New Zealand |
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