Cane toads ate my baby

A delayed account of zoological fieldwork in Australia – Part 13

From April 2010 I spent about five months undertaking several zoological field projects across Australia. I worked with government agencies, universities and NGOs on conservation and ecology studies ranging from Tasmanian devil facial tumour disease, the effect of fire, rain and introduced predators on desert ecology and how to poison cats. This series of blog posts is a delayed account of my time in the field.

Weeks Sixteen to Nineteen – part 2

Last week I described how we went about trapping small fauna at the Australian Wildlife Conservancy’s Wongalara sanctuary in the Northern Territory’s Top End. This week I want to talk about cane toads and some of the other feral beasts around.

Cane toads were released into Northern Queensland in order to control cane grubs – a pest on the lucrative sugar cane crop. Unfortunately their ecology made them completely unsuitable for such a task (the grubs live underground – toads hunt overground; the beetles live out in the open – toads live under cover). What happened instead was that toad populations rocketed and are still spreading in a terrifying wave westward and southward across the country, reaching the Top End about five years ago. Toads have decimated small mammal, reptile and amphibian populations through predation and have knocked out much above them in the food chain too, by poisoning anything that eats them. Just a couple of species of snake can deal with their toxin, and it seems crows have learned to flip them over only eat their bellies.

I was told early on that we wouldn’t catch many mammals here. The past three years’ month-long trapping trip they’ve caught 12, then 8, then 4. We only caught 5 this year. Watch this video and you might be able to guess why:

The number of toads at Wongalara was absolutely amazing. At night we would hear them crashing around everywhere, and see them every few metres. I was regularly woken by toads jumping against the walls of my tent. Some of them are huge and have no appealing features except their pretty gold-flecked eyes. There were 19 in one site one day. We didn’t catch much else there at all.

Killing cane toads

When we caught a toad in a trap we killed it with the quick and painless method of cervical dislocation. This was delivered with the sharp end of a shovel.

AWC’s policy to kill all toads is based on the premise that toads can eat things that they share a trap with. It was certainly true that if a toad was in a trap there were very rarely any other animals. The hope is that having removed the toads after the first night, fewer animals will be lost to them on the second and third nights. It’s frustrating because elsewhere, without toads, the first night is normally the most successful.

I’ve mentioned before in previous posts about poisoning cats that as a biologist, killing animals is a wholly unpleasant feeling. Some of the team out-right refused to do it. Cane toads exude a sticky white poison from their parotid glands when they feel threatened. I am pleased to say that it was very rare that a toad would release the poison when being killed, suggesting that they felt no pain in the process.

There are currently no good solutions for dealing with the cane toad problem. Any further release of predators or pathogens to control them would in all likelihood cause another Australian ecological catastrophe. And so killing them does feel like some action is being taken, however small-scale and ineffectual in the long-term.

Other ferals

Aside from cane toads, Wongalara is absolutely full of feral animals. Along with howling dingoes, donkeys would be braying, screaming and eeyoring constantly from around 4am to 7am. Every morning we would see tracks from buffalo that had run through our camp in the night, though we mainly only saw them from the trucks which they occasionally charged. I remember looking up from emptying a trap to see a massive bull buffalo staring at me from 20m away. The first response in such situations is to quickly identify the nearest climbable tree to escape to in the event of a charge. Although there were three people on the site, only one tree was big enough to hold a person. All of us spotted the buffalo and the tree. Thankfully it maintained its distance.

Feral boar were well established here too – the main evidence is the huge number of dried wallows that ruin the roads. One night one of the team, sleeping in a sack on the ground was well investigated.

It is a genuine shame that the ecology of this region wasn’t studied before cane toads arrived recently (AWC has only recently bought the property), or buffalo and pigs were introduced in the late nineteenth century. We’ll now never know the true effect on the local diversity of these introductions. This is something that is now being done in front of the toads advancing wave westward. As the toads make their way in to Western Australia data is being collected on the diversity of the regions before they arrive there (this is what I am doing on my next Australian trip next month to the Kimberley). Long-term studies will then be able to compare before and after data.

At Wongalara we would encounter a huge amount of deadly snakes in our traps. Next week I’ll look at how such tricky situations are dealt with.

UPDATE: PART FOURTEEN HERE