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Inferring diet, feeding behaviour and causes of mortality from prey-induced injuries in a New Zealand fur seal

journal contribution
posted on 2023-05-20, 22:12 authored by Hocking, DP, Marx, FG, Parker, WMG, Rule, JP, Cleuren, SGC, Mitchell, AD, Hunter, M, Bell, JD, Fitzgerald, EMG, Evans, AR

ABSTRACT: New Zealand fur seals Arctocephalus forsteri are the most abundant of the 4 otariid (eared seal) species distributed across Australasia. Analyses of stomach contents, scats and regurgitates suggest a diet dominated by bony fish and squid, with cartilaginous species (e.g. sharks and rays) either absent or underrepresented because of a lack of preservable hard parts. Here we report on a subadult specimen from south-eastern Australia, which was found ashore emaciated and with numerous puncture wounds across its lips, cheeks, throat and the inside of its oral cavity. Fish spines embedded in the carcass revealed that these injuries were inflicted by chimaeras and myliobatiform rays (stingrays and relatives), which matches reports on the diet of A. forsteri from New Zealand, but not South Australia. Shaking and tearing of prey at the surface may help to avoid ingestion of the venomous spines, perhaps contributing to their absence from scats and regurgitates. Nevertheless, the number and severity of the facial stab wounds, some of which led to local necrosis, likely affected the animal’s ability to feed, and may account for its death. Despite their detrimental effects, fish spine-related injuries are difficult to spot, and may be a common, albeit cryptic, type of trauma. We therefore recommend that stranded seals be systematically examined for this potentially life-threatening pathology.

History

Publication title

Diseases of Aquatic Organisms

Volume

139

Pagination

81-86

ISSN

0177-5103

Department/School

Institute for Marine and Antarctic Studies

Publisher

Inter-Research

Place of publication

Nordbunte 23, Oldendorf Luhe, Germany, D-21385

Rights statement

Copyright 2020 Inter-Research

Repository Status

  • Restricted

Socio-economic Objectives

Expanding knowledge in the biological sciences

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