Cane toads are a highly invasive species and are regarded as a major environmental pest in Australia. While there is fairly universal agreement over the need to control cane toads, there is significant debate over what is the most humane method to use. This is largely due to the limited research into the impact of killing methods on toads, exacerbated by the fact that it is difficult to measure pain and distress in amphibians through observation alone. Despite this, thousands of cane toads are killed every year in Australia by government and community groups and individuals, using many different (and sometimes very concerning) methods.

The RSPCA believes that any efforts to control cane toads should be carried out as part of a government or community organised program which includes clear guidelines on how toads should be handled and killed. However, there is also a need to provide practical advice to individuals who wish to humanely kill cane toads when they locate them on their property.

A recent study into the humaneness of a range of cane toad killing methods has brought into question the acceptability of a number of methods that have been widely used in the past. On the basis of this information, RSPCA Australia has reviewed our previous advice on this topic.

What killing methods can now be recommended?

Detailed information on the humane killing of cane toads is available in the Australian Government publication, Standard Operating Procedure for the Humane Field Euthanasia of Cane Toads which has been based on a comparative study of the humaneness of a range of different cane toad killing methods. Three methods are listed in the SOP as being conditionally acceptable:

1. Hopstop® is an aerosol spray that has been specifically developed for killing cane toads and is now commercially available for this purpose. When applied in sufficient quantity it appears to be an effective, easy to use and relatively humane method. Information on where to purchase Hopstop® is provided through the manufacturer's website: www.pestat.com.au/html/products.htm. It is very important that each toad is treated with sufficient spray to ensure it is anaesthetised and then killed quickly, so two sprays are required with the second applied after the toad has stopped moving. After 2 hours toads should be checks for signs of death before disposal. 
   


2. Stunning followed by decapitation can also be used to kill individual cane toads, but this method is only suitable for use by confident and skilled operators with the correct equipment and technique. This method must not be used unless those involved have received appropriate prior training, as ineffective stunning or unskilled decapitation will result in an inhumane death.
   


3. Prolonged exposure to carbon dioxide. The most commonly used method for killing multiple cane toads at a time has been exposure to carbon dioxide. This entails collecting toads in a plastic garbage bag and then filling the bag with carbon dioxide prior to disposal or burial. However it appears that the concentration and duration of exposure previously used does not actually kill cane toads, it merely anaesthetises them. This is one example of why it is so important to confirm death of a cane toad (or any animal) before disposing of its body. Research indicates that the use of carbon dioxide to kill cane toads is only effective and humane if exposure is maintained for at least 4 hours at 90% or greater concentration. The carbon dioxide must also be pre-warmed and the number of toads in each bag must not exceed 20 (in a 56 litre garbage bag). Death must be confirmed prior to disposal.

Cooling followed by freezing was previously cautiously recommended by the RSPCA, but this method has now been questioned due to concerns over whether toads may suffer during the cooling process prior to becoming insensible. The SOP also lists a number of other methods that are not considered acceptable.

How do I know when a cane toad is dead?

When using any killing method, it is essential that you confirm that the animal has died before disposing of its body. Determining death can be difficult with amphibians as their heart rate is difficult to detect and respiration can occur through the skin as well as the lungs. Absence of all of the following signs will confirm that the cane toad is dead (remember that you should wear thick plastic gloves when handling cane toads):

• Loss of righting reflex – the toad cannot turn itself over when placed onto its back
• Loss of withdrawal reflex - no response to a light squeezing of the skin in between the digits (fingers or toes)
• Loss of deep pain reflex – no response to moderate squeezing of the digits
• No respiratory movement – no throat movements that indicate breathing
• No heart activity – no chest movement or visible pulse

Always check for these signs and do not assume an animal is dead just because it is not moving or apparently not breathing. If any of these signs are detected, then you should repeat the killing procedure used.