Cane Toad in Australia
Cane toad species is invading Australia and is the largest in Bufonidae family. Adult cane toads weigh approximately 1.8 kg and are heavily built. Their sizes are approximately 10-23 cm with warty skin. They are colored olive-brown or reddish-brown and others yellow on the sides and back (Common wealth of Australia, 2009). They have unwebbed front feet while their back feet is strong and tough having leathery webbing. Their legs are short and their head ridged with bones. Their parotoid gland is located behind their ears causing swellings on their head. The gland produces poison for protection against predators, which is milky and toxic to many species. The poison affects heart functioning, burns eyes and causes skin irritation.
Australia is a home to unique species, which are remarkable in the world and must put extra efforts to protect them and save them from their predators. The culture of Australians is to benefit financially from the growth of sugarcane, but several insects invaded the plant and reduced their yields. White grub species devoured the roots, wire worms consumed the sett buds, stems are attacked by borers while armyworms, caterpillars, and grasshoppers consumed the leaves. Moth borers destroyed the shoot of the sugarcane. As a result, cane toads were introduced to eat the worms in sugar plantations. They replaced pesticides and copper among others, which were nasty and crude. Cane toads specialized in eating beetle larvae, which ate sugarcane roots (Australian Government, 2012).
Cane toads originated from Hawaii in June 1935 and were brought by Bureau of sugar experiment stations to eat Frenchi and grey back beetles that invaded sugarcane and increase yields (Common wealth Australia, 2010). Cane toads were by then better solutions compared to harmful DDT, which killed insects. However, today cane toads have increased to numerous numbers, which are raising concerns in Australian population.
Cane toads have multiplied at a faster rate in tropical Australia. In 1960s, there was slow invasion of toads with increases of 10km per year. Afterwards it slowly began to speed up to about 40 to 50 km each year because they travel long distances at night. Cane toads are found to travel faster than other toads or frogs in the world. They are forced to move faster and evolve and spread quickly due to pressures experienced by invaders.
Cane toads are spreading quickly to dry areas of Western Queensland. They are well established in Longreach area and other populations occupying Windorah area. In addition, toads are now moving to desert areas along River Victoria. Cane toads are posing a threat since they are adapting to harsh conditions in Australia.
Cane toad is a threat to Australian population due to its high toxic chemical effects on humans. Toads poison all predators attempting to eat them such as quolls, goannas, snakes, and crocodiles. There is increased competition for foods among other frogs such as green and golden type, threatening their survival (Common wealth of Australia, 2016). . Human habitat is reduced since cane toads occupy most of the land and a health concern due to their poison habits. Children are most affected by toad poisoning and pets. They are colonizing most of Australian land due to their high rates of reproduction. Cane toads have infested controlled lands of Australian government such as kakabu National park, indigenous protected areas, and World heritage areas.
Cane toads breed in still waters or slow speed waters. They tolerate up to 15% salinity levels. They survive temperatures ranging from 5-40 degrees. Their spawn includes a long gelatinous string with two rows of black eggs where females lay eggs approximately 35,000 eggs each time. They have a five years lifespan and breed twice a year (Doody et al., 2015). They achieve maturity from 6-18 months. They have the capacity to multiply to 2000 per hectare in suitable habitats and conditions. They move faster in wet seasons as they search for rehydration and breeding. In dry periods, they look for damp areas nearing creeks. Cane toads are a threat to most species since they develop most in warm waters, breed profusely in opportunistic conditions, and have greater productive rate.
Predation and competition
Cane toads are large consumers of invertebrates. They reproduce at a high rate and attain high densities, which colonize large areas. Cane toads consume more than 200 types of foods in a night including ants, termites, and beetle. They also eat insects, small frogs, reptiles, mammals, and birds. As a result, they compete for shelter and food with other animals leading to their decrease.
Lethal toxic ingestion
Northern Quoll was initially common in Queensland Australia. However, since introduction of Cane toad their distribution has declined with some species diminishing completely from southern Queensland. Studies show a 75% decline between 1900-1990. The main cause of their death being ingestion of poisonous cane toads and others like, fires, exotic diseases. Northern Quoll eats cane toads crushing them with their mouth, which causes a release of poison from the toad’s parotoid glands and is ingested into the system of Northern Quolls (Jolly, Shine & Greenlees, 2015).
All stages in the lifecycle of a cane toad are poisonous including eggs, tadpoles, toad lets, and adult toads. They have poison glands that secrete poison (parotoid glands) and store poison in their shoulder, which is released as they are threatened to predators. Ingestion of cane toads causes rapid heart beat, convulsions, paralysis, excess salivation which results in deaths of many animals. Cane tadpoles reduce chances of survival for native anurans by acting as predators. They have higher ability to compete for food thus reducing growth of other species. They poison small lizards and reduce food supplies of invertebrates. Cane toads caused a high mortality for bee-eater chicks by blocking their entrance into their nests.
Policies and approaches
There are plans by the Federal government to abandon their efforts of eradicating cane toads and start focusing on saving various areas and animals such as goanna and Quoll. The plans are established from studies indicating adaptation of native animals to cane toads into their environment. At risk, species are northern quoll, which became extinct after cane toad arrival (Common wealth of Australia, 2016).
Lessons from the case study
It is important to carry out tests before introducing any species to the environment to avoid causing further harm to the environment. In addition, more costs of reducing the menacing would be avoided by prior research. Cane toad introduction in Australia turned out to be a threat to humans and animal species. It is a threat to various species such as goannas, blue tounged lizard, and snakes. In addition, northern quoll and other invertebrates are at risk of being eaten by cane toads. Although cane toads were brought to control the spread and increase of pest beetles, they are now a threat to the human population and other species. It is worth noting that Federal government has spent $11 million on broad-scale control of cane toads and $9 million on cane toad research (Common wealth of Australia, 2016). Case study on cane toads and their effects helps people understand the importance of taking care of warnings given by scientists. Scientists who issued warnings and recommended pre-testing of potential impacts of the toad opposed the import of cane toad into Australia. There were no tests done by Australian researchers and no input of control measures. However, the effects of toads today have enforced strict quarantine laws and risk assessment procedures in Australia today.
New policies or approaches to cane toad control
Various approaches introduced aim at reducing the spread of toads in Australia. Fencing around dams located in Arid Australia could stop the menace of toads. The toads die in large numbers if they are trapped in dams as they look for water. Small fences are built surrounding dams along Victoria River. The fences are built of shade cloth and maintained for one year. The plans succeed since the toads cannot jump over or burrow under the fences. More toads died as they attempted to settles near fenced dams waiting to access water. Further studies indicate that toad population reduced by 100 times the original number (Molloy, K., & Henderson, 2010).
Frog watch policy is a project that aims to create awareness of toad cane in Australia to increase their knowledge on frogs and their impacts. Toad traps are placed in wetlands and focus on removing toads in people’s lands. Toad musters policy aims at picking up toads and removing them from their locality. Traps and musters are used during the wet season and most effective during the dry season to keep toads from land. Land care groups manage traps in wetlands. Community education aims at stopping toads through environmental awareness. Schools are a major focus for educating on toad cases (Molloy & Henderson, 2010). Developing frog pond with assistance from frog watch is a better approach since only native toads can utilize the facilities and be comfortable in them but cane toads cannot.
Research is done on cane toad and their population through observing a ring wood to monitor them. Introduction of native viral and bacterial pest for the toads is an option to control further invasion but has potential of invading native species. A focus on fecundity through release of sterile males to the population will only create male off springs, which would control reproduction rates and control population. Further research has shown that cane toad tadpoles are attracted by toxin produced by adults and spawn, while tadpoles cannibalize toad spawn as their food source. As a result, researchers have taken advantage of the toxin to lure the tadpoles of Cane to capture and eradicate them in controlled areas.
The government has listed biological effects, as well as ingestion of lethal toxic from cane toad as a threat under Environmental protection and Biodiversity conservation ACT 1999(EPBC Act).Australian government is establishing a threat plan to begin a research on management and necessary actions to increases survival for native species and ecosystem (Molloy & Henderson, 2010). It issued $2 million in 2008 and 2009 years on toad plan to conduct researches and development of control measures. Moreover, the government continuously works with regional natural resource management organizations to get desired outcomes on environment and sustainable agriculture.
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Molloy, K., & Henderson, W. (2010). Science of cane toad invasion and control. Proceedings of the invasive animals CRC/CSIRO/QID NRM&W cane toad workshop. Invasive animals cooperative research centre, 1-192.
Common wealth Australia. (2010).The cane toad (Bufo Marinus). Department of the environment, water, heritage, and the Arts, 1-4.
Common wealth of Australia. (2016). the biological effects, including lethal toxic ingestion, caused by Cane toads (Bufo marinus). Department of the environment. Australian government. Retrieved from http://www.environment.gov.au/biodiversity/threatened/key- threatening-processes/biological-effects-cane-toads
Jolly, C., Shine, R., & Greenlees, M. (2015).The impact of invasive cane toads on native wildlife in southern Australia. Ecol Evol journal, 5 (18), 3879-3894.
Australian government. (2012). Case study: Introduction of the cane toad to Australia. PETSMART, 1-2.
Doody,J.S.,Soanes,R.,Castellano,C.,Rhind,D.,Green,B.,Clulow,S.(2015). Invasive toads shift predator-prey densities in animal communities by removing top predators. Ecology journal, 1-10.
Australian government. (2012). Case study: introduction of the cane toad to Australia. PETSMART, 1-2. Retrieved from http://www.pestsmart.org.au/wp- content/uploads/2012/03/CTCS1.pdf