Reading group: Toxic Trojans

At QAECO we have a fortnightly reading group where we get together and discuss a paper, blog or piece of research – anything from seminal papers in ecology, new research, ideas from related fields, or just something we find interesting.

This is the first in a series of blog posts where we will be describing the papers we cover and the main points that come from our discussions.

This week’s paper was Toxic Trojans: can feral cat predation be mitigated by making their prey poisonous? which was recently published in Wildlife Research by John Read and colleagues.

This paper was chosen because it presents a novel idea for controlling feral predators. Predation by feral cats is a huge concern for conservation of Australian wildlife, as even low numbers of cats can drive population declines of native fauna and thwart reintroductions. However cat control is notoriously difficult as cats will rarely consume baits or enter baited traps when live prey are available.  There are also potential ethical concerns, such as the negative impacts of baiting on non-target species.

Feralcat_CMildwaters

Feral cat, Otway Ranges (image: C. Mildwaters)

 

John Read and colleagues (2015) present a novel strategy to add to the current arsenal of control methods: the use of Toxic Trojans — live prey that that appeal to the hunting instincts of cats but are lethal when consumed. They describe how Trojans have the potential to bolster reintroduction programs where predation by feral cats is the main impediment to population viability, and could be deployed as part of monitoring or management programs.

These Trojans could be created by fitting prey animals with collars that have a toxic attachment, inserting toxic implants under the skin of the prey (which do not harm the prey animal), or by supplement feeding toxin-tolerant prey with foods that render their tissues toxic to cats. The outcome is that the individual cats that target and consume the Trojans will be poisoned and thereby prevented from killing further individuals.

We were impressed by this innovation in feral cat control that aims to exploit the intrinsic hunting behaviour and biology of cats, while also capitalizing on the propensity of some wildlife to become poisonous to cats after consuming native plants. The method warrants further development and investigation. An important first step is to test some of the methods that could render prey toxic to find out if they could be safe for the Trojans and also effective in cat eradication. Ethical considerations also need to be more fully explored, for instance, could non-targets still be poisoned by consuming Trojans? And at what predation risk is it ethical to reintroduce species even with toxic Trojans?

A further step we discussed was using modelling to assess whether populations of threatened species would be viable under different scenarios of Trojan use. Comparisons could include the use of Trojans in strategic (the prey to protect is toxic) versus non-strategic (secondary prey toxic) ways, and under different patterns of territory re-invasion and varying likelihoods of individual cats becoming hunters of the target prey. The outcome of employing taste-aversion Trojans could be similarly modelled, as this seemed to us to be a particularly promising way of circumventing some of the previous issues with cat control, because the trained predator would remain within its territory and thereby exclude other non-trained individuals from killing the threatened prey.

With novel ideas on our minds, we took the opportunity to briefly touch on other innovative ideas in ecology including drones, gene-drive, and image recognition and its use in cat grooming-traps and star-fish eradication!

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