Whale carcass scavenging by sharks

Abstract

Sharks are well known to scavenge whale carcasses, but observations are rare. Here we (1) describe new observations of whale carcass scavenging behaviour by white (Carcharodon carcharias) and tiger (Galeocerdo cuvier) sharks, and (2) review the scientific and grey literature on the topic. Our new observations are from the east coast of New South Wales, Australia and include a sperm whale (Physeter microcephalus) carcass in 2015, a humpback whale (Megaptera novaeangliae) carcass and fin whale (Balaenoptera physalus) carcass in 2018. Analysis of these observations revealed that feeding preferences differed among whale species for each species of shark. Feeding behaviour (including test biting, head shaking, palatoquadrate protrusion, ocular rotation and nictitating membrane use) were employed by both tiger and white sharks, with little inter or intraspecific aggression. Behaviour of sharks scavenging whale carcasses differs in the primary literature depending on whale carcass and species of shark present. Most of our results support past observations regarding feeding behaviours and little inter or intraspecific aggression. However, our results differed from past events. We observed increased palatoquadrate protrusion by white sharks and avoidance of flukes or pectoral fins feeding by tiger and white sharks. Review of the literature demonstrates that scavenging events are more commonly reported in grey literature than in scientific documents.