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The red fox (Vulpes vulpes) as a potential invasive predator in a Critically Endangered sawfish nursery

David Morgan , Karissa Lear, Jack Ingelbrecht, Travis Fazeldean, Patricia Fleming

Abstract

Although the red fox (Vulpes vulpes) is considered one of the most damaging and adaptive invasive carnivorous mammals, consuming a wide variety of vertebrate and invertebrate taxa, there are surprisingly few reports of red foxes hunting fish. We observed evidence of an attempted predation event by a red fox on a neonate green sawfish (Pristis zijsron) within a deltaic island in the Ashburton River estuary, a remote desert river in Western Australia. The site is a globally important nursery where newborn sawfish arrive annually in spring. Injuries to the sawfish included paw/claw marks on the head, damage to the rostrum, which is a formidable tool that is used for both defence against predators and for detecting and attacking prey, as well as a major hole in the head and damage to the gills, which are vital for respiration, osmoregulation, nitrogenous waste excretion, pH regulation and hormone production. A series of tracks suggests at least one fox parades the shallow tidally influenced banks, with evidence of a green mud crab (Scylla serrata) having also been predated on. There have also been reports of red fox predation of sea turtle nests nearby. This is the first record of a red fox hunting in marine waters and one of the few identifying fish as prey. We suggest that a monitoring program for foxes, and possibly a control program, is warranted prior to the annual seasonal colonisation of this habitat by neonate green sawfish and nesting turtles which may in turn reduce predation of sympatric species.

PC24009  Accepted 19 December 2024

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