Paradoxical population resilience of a keystone predator to a toxic invasive species
J. Sean Doody
A B E , David Rhind C and Simon Clulow B D
+ Author Affiliations
- Author Affiliations
A Department of Biological Sciences, University of South Florida – St Petersburg, FL 33701, USA.
B School of Environmental and Life Sciences, University of Newcastle, Callaghan, NSW 2308, Australia.
C School of Biological Sciences, Monash University, Clayton, Vic. 3800, Australia.
D Department of Biological Sciences, Macquarie University, Sydney, NSW 2109, Australia.
E Corresponding author. Email: jseandoody@gmail.com
Wildlife Research 47(3) 260-266 https://doi.org/10.1071/WR19150
Submitted: 24 August 2019 Accepted: 23 November 2019 Published: 13 May 2020
Abstract
Context: The invasive cane toad (Rhinella marina) has decimated populations of a keystone predator, the yellow-spotted monitor (Varanus panoptes), causing trophic cascades in Australian animal communities. Paradoxically, some V. panoptes populations coexist with toads. Demonstrating patterns in heterogeneous population-level impacts could reveal mechanisms that mediate individual effects, and provide managers with the ability to predict future impacts and assist in population recovery.
Aims: The aim of the present study was to search for spatial patterns of population resilience of V. panoptes to invasive cane toads.
Methods: Published literature, unpublished data, reports and anecdotal information from trained herpetologists were used to test the emerging hypothesis that resilient predator populations are mainly coastal, whereas non-resilient populations are mostly inland.
Key results: Post-toad invasion data from 23 V. panoptes populations supported the idea that toad impacts on V. panoptes were heterogeneous; roughly half the populations could be designated as resilient (n = 13) and half as non-resilient (n = 10). Resilient populations had longer times since toad invasion than did non-resilient populations (39 versus 9 years respectively), supporting the idea that some recovery can occur. Non-resilient populations were exclusively inland (n = 10), whereas resilient populations were split between inland (n = 5) and coastal (n = 8) populations. Resilient inland populations, however, were mainly confined to areas in which decades had passed since toad invasion.
Conclusions: The findings suggest that coastal V. panoptes populations fare much better than inland populations when it comes to surviving invading cane toads.
Implications: Unambiguous recovery of monitor populations remains undemonstrated and will require long-term population monitoring before and after toad invasion.
Additional keywords: abundance, behaviour, ecology, invasive species, pest management.
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