Factors affecting the frequency and outcome of platypus entanglement by human rubbish

Abstract

The platypus’s tapered shape and benthic foraging habits predispose it to becoming entangled in encircling rings or loops of plastic, rubber or metal rubbish. Based on 54 cases of litter entanglement recorded in Victorian live-trapping surveys, items may encircle the neck (68%), torso (8%), jaw (2%) or be wrapped bandolier-fashion from in front of a shoulder to behind the opposite foreleg (22%). Entanglement frequency was eight times higher in the greater Melbourne region than in regional Victoria, and was significantly greater in first-year juveniles than in older animals and also in adult/subadult females compared with adult/subadult males. Items recovered from carcasses or from rescued animals that were unlikely to have survived without human intervention included elastic hair-ties, fishing line, a hospital identification wristband, an engine gasket and a plastic ring seal from a food jar; all of these items had cut through skin and (in most cases) deeply into underlying tissue. Up to 1.5% of the platypus residing in the greater Melbourne area and 0.5% of those living in regional Victoria are estimated to be at risk of entanglement-related injuries or death at any point in time.