Choose your meals carefully if you need to coexist with a toxic invader

Lachlan Pettit,Georgia Ward-Fear,Richard Shine

doi:10.1038/s41598-020-78979-8

Lachlan Pettit, Georgia Ward-Fear + Show 1 more

Open Access

https://doi.org/10.1038/s41598-020-78979-8

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Journal: Scientific Reports	Publication Date: Dec 1, 2020
Citations: 7	License type: open-access

Affiliation: Macquarie University, University of Sydney

Abstract

Vulnerable native species may survive the impact of a lethally toxic invader by changes in behaviour, physiology and/or morphology. The roles of such mechanisms can be clarified by standardised testing. We recorded behavioural responses of monitor lizards (Varanus panoptes and V. varius) to legs of poisonous cane toads (Rhinella marina) and non-toxic control meals (chicken necks or chicken eggs and sardines) along 1300 and 2500 km transects, encompassing the toad’s 85-year invasion trajectory across Australia as well as yet-to-be-invaded sites to the west and south of the currently colonised area. Patterns were identical in the two varanid species. Of monitors that consumed at least one prey type, 96% took control baits whereas toad legs were eaten by 60% of lizards in toad-free sites but 0% from toad-invaded sites. Our survey confirms that the ability to recognise and reject toads as prey enables monitor lizards to coexist with cane toads. As toxic invaders continue to impact ecosystems globally, it is vital to understand the mechanisms that allow some taxa to persist over long time-scales.

Highlights

Vulnerable native species may survive the impact of a lethally toxic invader by changes in behaviour, physiology and/or morphology
A vulnerable native species may evolve shifts in physiology or morphology that render an individual less vulnerable to an encounter with the invader[7,8]. All three of these pathways have been reported in the case of native species impacted by the spread of cane toads (Rhinella marina) through Australia
It seems likely that monitors survive toad invasion by developing taste aversion rather than by shifts in morphology or physiology

Summary

Introduction

Vulnerable native species may survive the impact of a lethally toxic invader by changes in behaviour, physiology and/or morphology. A vulnerable native species may evolve shifts in physiology (e.g., toxin tolerance) or morphology (e.g., relative head size, and maximum ingestible prey size) that render an individual less vulnerable to an encounter with the invader[7,8] All three of these pathways (changes in behaviour, physiology and morphology) have been reported in the case of native species impacted by the spread of cane toads (Rhinella marina) through Australia. We recorded behavioural responses of monitor lizards (Varanus panoptes and V. varius) to legs of toxic cane toads and non-toxic control meals along 1300 and 2500 km transects, encompassing the toad’s 85-year invasion trajectory across Australia as well as yet-to-be-invaded sites to the west and south of the currently colonised area. We hypothesised that lizards in areas long colonised by toads would avoid eating toxic prey items

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