Source document: https://docs-lawep.s3.us-east-2.amazonaws.com/1697643831530.pdf (Australia)
Submission to House of Representatives Standing Committee on the Environment and Energy Inquiry into controlling the spread of cane toads Prof Lin Schwarzkopf, College of Science and Engineering, James Cook University, Douglas, QLD 4811 ‘ “Control Methods for Toads Should Avoid Unintended Consequences” Summary — Toads are an increasing threat to the Australian environment, given their high reproductive rate, high movement and dispersal rates, and their ability to persist in wilderness areas where they have significant impacts on vertebrate predators and invertebrate prey.
Their ability to poison native predators that attempt to consume them is well-known.

Perhaps less appreciated is their ability to consume significant numbers of invertebrates, with negative impacts on both invertebrates directly, and other insectivorous species that need to eat insects to survive.

Through their impacts on predators, and especially on invertebrates and insectivores, cane toads may have significant, but underappreciated impacts on a wide range of threatened species in Australia.
Because of their impact on wildlife, it is critical to reduce toad numbers, and to avoid control methods which include potential unintended consequences that may increase numbers of toads.

Trapping of reproductive females provides a method that reduces cane toad numbers (Muller et al.

2018a) before they reach water bodies as tadpoles, and although it is expensive and requires expertise, support for research to allow improvement of traps could reduce these negatives.
Term of Reference 1: The effectiveness of control measures to limit the spread of cane toads in Australia.

Because they are relatively small, disperse quickly and easily when the ground is wet (Muller et al 2018b), and reproduce in very large numbers, cane toads are difficult to control.

There are a variety of methods that have been suggested for their control (most recently summarised in Tingley et al.

2017).
2017).

Cane toads are present all across the tropics of Australia, and continue to spread westwards and southwards.

They are very numerous, they occur in very hard-to-reach and remote areas, and the ‘front’ areas are very wide, and therefore they are very difficult to manage.

Realistically, eradication of toads in Australia is unlikely, no matter the method, and most proposed control measures are likely to provide suppression of numbers.
Suppression of numbers is an important aspect of cane toad control, I would strongly recommend that any method of control that is supported include suppression of numbers.

Why is suppression of numbers of toads important?

Cane toads have toxic glands that cause mortality in many predators in the Australian environment.
The mortality of native predators is the most visible aspect of their impact, and some of the control measures that have been recommended involve reducing the toxicity of toads using gene editing (Tingley et al.

2017).

Similarly, there have been recommendations to release small toads ahead of the front.

Such methods are designed to reduce harm by reducing toad threats to predators.
It is important, 1 Inquiry into controlling the spread of cane toadsSubmission 21 however, to remember that toads also have impacts on invertebrate prey and on their competitors, which are also negative, and are much harder to measure (Greenlees et al.

2007).
2007).

Methods that reduce toad threats to predators but do not reduce numbers reduce some of the threats posed by toads, but do not reduce numbers (and may actually increase numbers, in some cases), thereby potentially increasing the other threats of toads.

The committee should consider the impact of control measures carefully in their deliberations.

It will be necessary to use a variety of measures to control toads, and I recommend an integrated control approach, using a variety of methods.
Such methods should include mechanical means of removal, such as traps.

Traps should target reproductive individuals, especially gravid females (Yaeger et al.

2014; Davis et al.

2015; Muller & Schwarzkopf 2017; 2018).

Traps using a acoustic lure in combination with a food lure (Yaeger et al.
2014) target gravid females and remove them from the breeding population (Muller & Schwarzkopf 2017) before tadpoles appear in the environment, obviating the negative impacts of tadpoles on other tadpoles and fish (Crossland 2001; Crossland & Shine 2010).

There are other reasons why trapping adult females, at least at the same time as tadpole trapping, is necessary.
Tadpole trapping in the absence of trapping of adult females could, counterintuitively, cause more cane toad juveniles to emerge from a water body than if no tadpole trapping was conducted.

This could occur because cane toad tadpoles can reach very high numbers in water bodies, and cane toad tadpoles (like many tadpoles) compete most strongly with other cane toad tadpoles, limiting their growth (Crossland & Shine 2010).
Thus, trapping tadpoles could have the unintended consequence of not changing, or even increasing, numbers of juveniles emerging from water bodies, because competitive success of cane toad tadpoles is increased if most other cane toad tadpoles are removed.
I recommend trapping adults in the same locations when trapping tadpoles, to ensure that females are removed before breeding, as well as removing tadpoles after breeding, to ensure that numbers of toads are reduced, rather than not changed, or, worse, increased.

Traps of any kind cannot be deployed over very wide areas, because of the difficulty of monitoring them, and therefore they are best deployed in urban and peri-urban locations where they can be monitored closely.
In addition, to reduce numbers in less accessible areas, it will be necessary to conduct research on other methods of controlling toads that will reach a broad area.

If such a method is discovered, traps could be used to collect toads to help disseminate any sort of genetic disease or parasite that future research finds.

Term of Reference 2: Additional support for cane toad population control measures.

Additional support is definitely needed for cane toad population control measures.
Many present government pest control initiatives have focussed on pests of both agriculture and the environment, and as cane toads are environmental, but not agricultural pests, their control has not been supported recently.

Most of the methods we have are very new, or are only ideas, and require more support for testing and implementation.
2 Inquiry into controlling the spread of cane toadsSubmission 21 Priorities for investment in toad control: Trapping adults is an excellent method of reducing numbers of many vertebrate pests, including toads, and is the only known method to control gravid females (Muller et al 2017, 2018a), but trapping adults is very expensive, and limited in scope because it requires personnel to monitor traps daily.
Travel time and expertise, including amphibian species recognition, and humane disposal of pests is required, increasing expense.

There is the potential to develop automated methods of detecting and disposing of animals to reduce the need for trap monitoring and maintenance, but this needs to be refined to eliminate bycatch.

Development of such methods would allow traps to be deployed in areas with little access, and greatly increase the reach of mechanised methods to control toads into remote areas.
Development includes the development of automated recognition methods (e.g., Konovalov et al.

2018) and of automated disposal methods for toads in the wild.

Such methods may increase the reach of the only known control method that removes gravid females from populations.

References Crossland, M. R. (2001).

Ability of predatory native Australian fishes to learn to avoid toxic larvae of the introduced toad Bufo marinus.

Journal of Fish Biology, 59(2), 319-329.

Crossland, M. R., & Shine, R. (2010).


Vulnerability of an Australian anuran tadpole assemblage to the toxic eggs of the invasive cane toad (Bufo marinus).

Austral Ecology, 35(2), 197-203.

Davis, J. L., Alford, R. A., & Schwarzkopf, L. (2015).

Some lights repel amphibians: implications for improving trap lures for invasive species.

International journal of pest management, 61(4), 305-311.

Greenlees, M. J., Brown, G. P., Webb, J. K., Phillips, B. L., & Shine, R. (2007).
Do invasive cane toads (Chaunus marinus) compete with Australian frogs (Cyclorana australis)?.

Austral Ecology, 32(8), 900-907.

Konovalov, D. A., Jahangard, S., & Schwarzkopf, L. (2018, December).

In Situ Cane Toad Recognition.

In 2018 Digital Image Computing: Techniques and Applications (DICTA) (pp.

1-7).

IEEE.

Muller, B. J., & Schwarzkopf, L. (2017).

Success of capture of toads improved by manipulating acoustic characteristics of lures.

Pest management science, 73(11), 2372-2378.


Muller, B. J., & Schwarzkopf, L. (2018a).

Relative effectiveness of trapping and hand-capture for controlling invasive cane toads (Rhinella marina).

International Journal of Pest Management, 64(2), 185-192.

Muller, B. J., Cade, B. S., & Schwarzkopf, L. (2018b).

Effects of environmental variables on invasive amphibian activity: using model selection on quantiles for counts.

Ecosphere, 9(1).
Ecosphere, 9(1).

3 Inquiry into controlling the spread of cane toadsSubmission 21 Tingley, R., Ward-Fear, G., Schwarzkopf, L., Greenlees, M.J., Phillips, B.L., Brown, G., Clulow, S., Webb, J., Capon, R., Sheppard, A.

& Strive, T. (2017).

New weapons in the Toad Toolkit: a review of methods to control and mitigate the biodiversity impacts of invasive cane toads (Rhinella marina).

The Quarterly review of biology, 92(2), 123-149.

Yeager, A., Commito, J., Wilson, A., Bower, D., & Schwarzkopf, L. (2014).
Sex, light, and sound: location and combination of multiple attractants affect probability of cane toad (Rhinella marina) capture.

Journal of pest science, 87(2), 323-329.

4 Inquiry into controlling the spread of cane toadsSubmission 21