Title

Impacts of the Invasive Cane Toad on Aquatic Reptiles in a Highly Modified Ecosystem: The Importance of Replicating Impact Studies

Department

Natural Sciences

Document Type

Article

Publication Source

Biological Invasions. Volume 16, Issue 11, Pages 2303–2309.

Publication Date

2014-11

Abstract

Invasive species can have dramatic and detrimental effects on native species, and the magnitude of these effects can be mediated by a plethora of factors. One way to identify mediating factors is by comparing attributes of natural systems in species with heterogeneity of responses to the invasive species. This method first requires quantifying impacts in different habitats, ecosystems or geographic locations. We used a long-term, before-and-after study to quantify the impacts of the invasive and toxic cane toad (Rhinella marina) on two predators in a highly modified ecosystem: an irrigation channel in an agricultural landscape. Survey counts spanning 8 years indicated a severe population-level decline of 84 % in Merten’s Water Monitor (Varanus mertensi) that was coincident with the arrival of cane toads. The impact of cane toads on V. mertensi was similar to that found in other studies in other habitats, suggesting that cane toads severely impact V. mertensi populations, regardless of habitat type or geographic location. In contrast, a decline was not detected in the Freshwater Crocodile (Crocodylus johnstoni). There is now clear evidence that some C. johnstoni populations are vulnerable to cane toads, while others are not. Our results reinforce the need for the replication of impact studies within and among species; predicting impacts based on single studies could lead to overgeneralizations and potential mismanagement.

Keywords

lethal toxic ingestion, heterogeneity in responses, agricultural landscape, monitor lizard, crocodile, rhinella

DOI

10.1007/s10530-014-0665-6

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