Cane Toad
Cane Toad - Rhinella marina
Impacts
The main threat posed by cane toads occurs when other wildlife attempt to eat them. When cane toads are threatened, they release a toxin (bufotoxin) from the glands behind the eyes and across their back. This toxin is present in both the adults and tadpoles, meaning that cane toads may negatively impact a wide diversity of wildlife.
While it has been very difficult to quantify the losses to native animals as a result of cane toad invasion, evidence suggests that the northern quoll, goannas, snakes, fish, freshwater crocodiles and egrets are particularly affected by the invasion of cane toads. In parts of Queensland, populations of some of these animals were dramatically reduced when cane toads first arrived, although it seems that many have recovered since that time. This recovery has mainly been attributed to a change in behaviour, as native animals have learned to avoid cane toads as a food source.
Other threats to native wildlife include competition with native animals for food and resources and increased spread of disease.
Background
Cane toads are native to Central and South America. They were first introduced to Australia (Queensland) in the 1930's as a means of controlling the cane beetle, which was causing significant damage to sugar cane crops. Cane toads have spread fairly rapidly through northern Australia, and they are now located in Queensland, New South Wales and the Northern Territory. In fact, few people realise that cane toads were first sighted in the Northern Territory in 1984. However, more recent sightings of cane toads in the Darwin region has resulted in greater public interest. Considerable activity is currently being invested into preventing cane toads from spreading into Western Australia.
Cane toads are prolific breeders, which is one of the primary reasons for their considerable invasion success. In addition, they are opportunistic feeders, and their diet comprises both living and dead matter such as plants, carrion, dog food, household refuse, small vertebrates, and a range of invertebrates. Other characteristics that add to their invasion success in Australia, and in other locations, include their capacity to live for extended periods away from water, their ability to tolerate sea water for short periods, and their nocturnal activity.
Distribution and Habitat
Cane toads can exist in many different habitats but must have water available to breed. During the Dry Season, toads remain inactive in shallow burrows under the ground, or in clusters under logs, rocks or sheets of iron, etc. They are mainly nocturnal. Cane toads can also survive for periods in sea water. There are accounts of adult cane toads swimming at sea in Bermuda, Mexico and Jamaica. They have been similarly sighted swimming in the McArthur estuary in the Gulf country of the Northern Territory and may have colonised Kangaroo Island (NT) in this way.
View ToadScan website (Invasive Animal CRC) which maps sightings, damage and events to do with cane toads all over Australia.
Life Cycle
Toads are prolific breeders compared to native frogs. They can breed twice a year and lay 10 000 to 20 000 eggs each breeding. Their eggs can hatch in 2 days and look different to frogs’ eggs as they are laid in thin strands of clear jelly.
The cane toad tadpole is much smaller than native tadpoles. Eggs, tadpoles and toadlets are all toxic, but only some animals die when they eat them.
Management
The Northern Territory Government provides considerable funding to Frogwatch each year to assist in community cane toad management.
One of the main functions that Parks and Wildlife NT are involved in is educating the public about toads. There are 3 important steps to follow if you think you have found a toad.
Identify the animal.
In the last 5 years, our officers have been called on to identify many suspected cane toads sighted in Darwin. 95% of these animals were identified as Marbled Frogs or other native species. Some of these native frogs had been killed. People from interstate have never seen Marbled Frogs, a common Darwin native species and their warty appearance and large size fools many people. Please be sure that you really do have a cane toad before killing it.
Use a safe method to collect the toad.
Cane toads are toxic. The source of the toxins is a large gland on the back of the neck. It is only toxic if ingested or rubbed into eyes. The toxin exudes over the toad's skin, it does not spurt out. Use two plastic shopping bags, or something similar to pick up the toad. Turn the bags inside out, grab the toad, turn the bags the correct way round again, tie the bags tightly and you'll have safely bagged your toad.
Disposing of the toad.
We have all heard stories of how people in other places kill cane toads. The most humane method of disposing of toads is to place your double-bagged toad in the freezer overnight.