Stop the invasion: enhancing the effectiveness of trapping methods to control cane toads (Rhinella marinus)

Cane toads (Rhinella marina) are a significant ecological problem, but there are, as yet, no effective, long-term techniques available to control them. Thus, trapping may be effective in the short-term, or even as a longer-term method incorporated into integrated pest control for toads. Presently traps include a white fluorescent light as a lure. We used laboratory experiments and field trials to investigate better lures for toads, to improve trapping success. Laboratory experiments and field trapping exercises clearly demonstrated that: 1. Toads were not attracted to lights. We found that toads respond differently to different light types; were repelled by some, and showed no preference for others, but none of the lights we tested attracted toads. Anecdotal evidence suggesting that toads are attracted to lights has apparently arisen because, in urban environments, toads are attracted to insects attracted to lights. 2. UV 'black' lights neither attracted or repelled toads in laboratory experiments. Yellow ‘anti-insect’ fluorescent lights, and UV 'black' lights were neither attractive nor repellant to toads when tested in comparison to darkness. When tested against each other, toads appeared to prefer UV 'black' lights. 3. We strongly recommend the use of UV 'black' lights on traps in the field. Using UV 'black' lights compared to white lights on traps in the field increased trapping success approximately 10-fold. 4. Cane toad calls in north Queensland are, on average, 8.2 sec long (range 2.4 -16.6 sec), have a mean dominant frequency of 613.7 Hz (range 524.9 – 753.6 Hz), have 15.3 pulses per second on average (range 14 – 17), and intercall intervals ranging from 3 – 47.7 sec (12. 1 sec on average). We used these values to create an 'average' toad call characteristic of toad calls in north Queensland, and to parameterise modified calls both within and outside normal call ranges. 5. In an experimental arena, cane toads were attracted to modified 'average' calls, and calls with low dominant frequency, high pulse rates, and a combination call with low dominant frequency and high pulse rate, within the range of natural calls. Male toads investigated most calls approximately equally. Female toads were not attracted to high dominant frequency, low pulse rate, or combination calls that had dominant frequencies and pulse rates outside (higher than) the natural range. 6. Using a toad call created using local calls is an effective attractant on traps. Traps equipped with an 'average' toad call, parameterized and then created using the above values, were significantly more attractive than traps equipped with UV 'black' light alone. 7. Both cage traps and trap door traps make good capture devices for toads. There was no significant difference between cage traps and trapdoor traps in terms of numbers of toads captured. Either kind of trap was adequate for toad capture, and small variations over short periods in capture success, perhaps due to trap placement, influence success of both trap types. 8. Using a 'super' call (constructed using a high pulse rate and low dominant frequency relative to average calls, but within natural ranges) is a better attractant than normal calls for controlling toads using traps, because it is highly attractive to females. Manipulated 'super calls' were not significantly more attractive in terms of numbers of toads attracted compared to normal calls. However, super calls attracted twice as many females as normal calls. Control of toads would be more effective if breeding adult females were removed from the population being trapped, so we recommend the use of super calls on traps. 9. Place traps on tracks. Our results suggest that trap placement is an important variable influencing capture success. Placing the trap on an open roadway (a dirt track) increased trap success over 50% compared to placement in vegetation near a track, or in vegetation. 10. Toad calls work more effectively than insect calls as attractants on traps. We found that the calls of a large local insect, consumed by toads, were less attractive than toad calls on traps. 11. Carrion smells did not increase number of captured toads over UV 'black' light alone