Humpback whales interfering when mammal-eating killer whales attack other species: mobbing behavior and interspecific altruism?

Pitman, Robert L., Deecke, Volker B., Gabriele, Christine M., Srinivasan, Mridula, Black, Nancy, Denkinger, Judith, Durban, John W., Mathews, Elizabeth A., Matkin, Dena R., Neilson, Janet L., Schulman-Janiger, Alisa, Shearwater, Debra, Stap, Peggy and Ternullo, Richard (2016) Humpback whales interfering when mammal-eating killer whales attack other species: mobbing behavior and interspecific altruism? Marine Mammal Science, 33 (1). pp. 7-58.

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Official URL: https://doi.org/10.1111/mms.12343

Abstract

Humpback whales (Megaptera novaeangliae) are known to interfere with attacking killer whales (Orcinus orca). To investigate why, we reviewed accounts of 115 interactions between them. Humpbacks initiated the majority of interactions (57% vs. 43%; n=72), although the killer whales were almost exclusively mammal-eating forms (MEKWs, 95%) vs. fish-eaters (5%; n=108). When MEKWs approached humpbacks (n=27), they attacked 85% of the time and targeted only calves. When humpbacks approached killer whales (n=41), 93% were MEKWs, and >87% of them were attacking or feeding on prey at the time. When humpbacks interacted with attacking MEKWs, 11% of the prey were humpbacks and 89% comprised 10 other species, including 3 cetaceans, 6 pinnipeds, and 1 teleost fish. Approaching humpbacks often harassed attacking MEKWs (>55% of 56 interactions), regardless of the prey species, which we argue was mobbing behavior. Humpback mobbing sometimes allowed MEKW prey, including nonhumpbacks, to escape. We suggest that humpbacks initially responded to vocalizations of attacking MEKWs without knowing the prey species targeted. Although reciprocity or kin selection might explain communal defense of conspecific calves, there was no apparent benefit to humpbacks continuing to interfere when other species were being attacked. Interspecific altruism, even if unintentional, could not be ruled out.

Item Type: Article
Journal or Publication Title: Marine Mammal Science
Publisher: Wiley / Society for Marine Mammalogy
ISSN: 1748-7692
Departments: Centre for Wildlife Conservation
Faculty of Health and Science > Science, Natural Resources and Outdoor Studies > Forestry, Conservation & Applied Science
Additional Information: This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.
Depositing User: Volker B. Deecke
Date Deposited: 10 Jun 2016 15:48
Last Modified: 24 Jul 2017 10:05
URI: http://insight.cumbria.ac.uk/id/eprint/2239

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