Population‐level declines in Australian predators caused by an invasive species

  title={Population‐level declines in Australian predators caused by an invasive species},
  author={J. Sean Doody and Brenna Green and David W. Rhind and Christina M. Castellano and Rebecca Sims and Thomas Robinson},
  journal={Animal Conservation},
The cane toad Bufo marinus has been migrating westward across northern Australia since its introduction as a biological control agent in 1935. It has been implicated in the widespread decline of many native frog‐eating predators. To investigate the impacts of this invasive species on native predatory reptiles, annual surveys were conducted from 2001 to 2007 to document variation in the relative abundances of three varanid lizards (Varanus mertensi, Varanus mitchelli and Varanus panoptes) and… 

The impact of invasive cane toads on native wildlife in southern Australia

The invasion of cane toads through temperate‐zone Australia appears to have reduced populations of at least four anurophagous predators, facilitated other taxa, and decreased rates of scavenging.

The Ecological Impact of Invasive Cane Toads (Bufo Marinus) in Australia

  • R. Shine
  • Environmental Science
    The Quarterly Review of Biology
  • 2010
A review of these studies suggests that a single pathwaylethal toxic ingestion of toads by frog-eating predators is the major mechanism of impact, but that the magnitude of impact varies dramatically among predator taxa, as well as through space and time.

Long‐term monitoring reveals declines in an endemic predator following invasion by an exotic prey species

Declines in an Australian freshwater crocodile Crocodylus johnstoni population following invasion of a toxic prey species, the cane toad Rhinella marina, highlight the importance of long-term monitoring programmes for quantifying the impacts of novel and unforeseen threats.

Invasive toads shift predator-prey densities in animal communities by removing top predators.

The consensus of the original and published long-term data is that invasive cane toads are causing predators to lose a foothold on top-down regulation of their prey, triggering shifts in the relative densities of predator and prey in the Australian tropical savannah ecosystem.

Divergent long-term impacts of lethally toxic cane toads (Rhinella marina) on two species of apex predators (monitor lizards, Varanus spp.)

The impact of cane toads on apex predators has been exacerbated and prolonged by a scarcity of alternative prey, and multiple anthropogenically-induced changes to natural ecosystems may have synergistic effects, intensifying the impacts beyond that expected from either threat in isolation.

Behavioural responses of reptile predators to invasive cane toads in tropical Australia

Intraspecific variation in responses means that even in taxa that apparently are unaffected by toad invasion at the population level, some individual predators nonetheless may be fatally poisoned by invasive cane toads.

Why does vulnerability to toxic invasive cane toads vary among populations of Australian freshwater crocodiles?

It is suggested that spatial variation in the availability of alternative prey (and thus the willingness of crocodiles to attack a novel toxic prey item) may have contributed to that variation in impact.

Chronic effects of an invasive species on an animal community.

Results indicate a system still in ecological turmoil, having not yet reached a "new equilibrium" more than a decade after the initial invasion, and suggest that recovery of impacted predators must occur unassisted by evolutionary means: dispersal into extinction sites from surviving populations with alleles for toxin resistance or toad avoidance.

Invasive species-driven trophic cascades: Are cane toads indirectly contributing to small mammal collapses across tropical Australia?

A novel conceptual model is postulate linking recent mammal declines with trophic cascades following toad invasion, where the loss of large, anurophagous (toad-eating) reptilian apex predators allowed increases in mammal-eating meso-predatory snakes and large lizards.

A review of ecological interactions between native frogs and invasive cane toads in Australia

  • R. Shine
  • Environmental Science, Biology
  • 2013
Information on ecological interactions between cane toads and Australian anurans is reviewed to offer a cautionary tale about the difficulty of predicting the impact of an invasive species, even with a clear understanding of mechanisms of direct interaction.



Cane toads reduce the abundance and site occupancy of Merten’s water monitor (Varanus mertensi)

There has been demonstrable change in the abundance and proportion of sites occupied by V. mertensi following the colonisation of cane toads, but the population has been able to persist.

Indirect impacts of invasive cane toads (Bufo marinus) on nest predation in pig-nosed turtles (Carettochelys insculpta)

Data and observations indicate that cane toads arrived at the study sites during the wet seasons of 2003–04 and 2004–05, and the lizard V. panoptes has been reduced to such low numbers that it is currently no longer a significant predator of pig-nosed turtle eggs.

Colonizing Cane Toads cause population declines in native predators: reliable anecdotal information and management implications

This paper presents compelling, anecdotal evidence of severe population declines in five predator species, Dasyurus hallucatus, Varanus gouldii, V. mertensi, V. panoptes, and V. timorensis similis,

Assessing the Potential Impact of Cane Toads on Australian Snakes

Overall, the analysis suggests that cane toads threaten populations of approximately 30% of terrestrial Australian snake species, with a similar low ability to tolerate toad toxins.

Does intraspecific niche partitioning in a native predator influence its response to an invasion by a toxic prey species

It is suggested that cane toads may negatively affect populations of northern death adders in the Darwin region, and it is predicted that different size and sex classes of A. praelongus will experience differential mortality rates over different timescales.

Feral pigs facilitate hyperpredation by golden eagles and indirectly cause the decline of the island fox

It is shown that the introduction of feral pigs to the California Channel Islands has sustained an unnaturally large breeding population of golden eagles, a native predator, and hypothesize that this interaction ultimately stems from human-induced perturbations to the island, mainland and surrounding marine environments.

Toxic tucker: the potential impact of Cane Toads on Australian reptiles

It is concluded that toads pose a real and ongoing threat to the majority of Australian reptile species and all of Australia's crocodiles and freshwater turtles are potentially at risk from toads.

Changes in mammal populations in relatively intact landscapes of Kakadu National Park, Northern Territory, Australia

Observations suggest that the biota of the vast relatively undisturbed tropical savannas of northern Australia can no longer be assumed to be intact nor safe.

Spawning site selection by feral cane toads (Bufo marinus) at an invasion front in tropical Australia

C cane toads broadly resemble previously studied toad species in other parts of the world, as well as conspecifics within their natural range in South America.

Rapid expansion of the cane toad (Bufo marinus) invasion front in tropical Australia

Surveys of the location of the toad invasion front in 2001 to 2005, and radiotracking of toads at the front near Darwin in 2005, reveal much faster westwards expansion than was recorded in earlier stages of toad invade through Queensland.