Distribution:
The cane toad is native to the Americas, and its range stretches from the Rio Grande Valley in southern Texas to the central Amazon and south-eastern Peru. This area encompasses both tropical and semi-arid environments.
The density of the cane toad is significantly lower within its native distribution than in places where it has been introduced. In South America, the density was recorded to be 20 adults per 100 metres (109 yards) of shoreline, 50–100 times lower than the density in Australia.
The cane toad has been introduced to many regions of the world—particularly the Pacific—for the biological control of agricultural pests. These introductions have generally been well documented, and the cane toad may be one of the most studied of any introduced species.
Before the early 1840s, the cane toad had been introduced into Martinique and Barbados, from French Guiana and Guyana. An introduction to Jamaica was made in 1844 in an attempt to reduce the rat population.
Despite its failure to control the rodents, the cane toad was introduced to Puerto Rico in the early 20th century in the hope that it would counter a beetle infestation that was ravaging the sugarcane plantations.
The Puerto Rican scheme was successful and halted the economic damage caused by the beetles, prompting scientists in the 1930s to promote it as an ideal solution to agricultural pests.
As a result, many countries in the Pacific region emulated the lead of Puerto Rico and introduced the toad in the 1930s. There are introduced populations in Australia, Florida, Papua New Guinea, the Philippines, the Ogasawara and Ryukyu Islands of Japan, most Caribbean islands, Fiji and many other Pacific islands. including Hawaii.
Since then, the cane toad has become a pest in many host countries, and poses a serious threat to native animals.
Australia:
Following the apparent success of the cane toad in eating the beetles that were threatening the sugarcane plantations of Puerto Rico, and the fruitful introductions into Hawaii and the Philippines, there was a strong push for the cane toad to be released in Australia to negate the pests that were ravaging the Queensland cane fields.
As a result, 102 toads were collected from Hawaii, equally comprising males and females, and brought to Australia. After an initial release in August 1935, the Commonwealth Department of Health decided to ban future introductions until a study was conducted into the feeding habits of the toad.
The study was completed in 1936 and the ban lifted, at which point large scale releases were undertaken—by March, 1937, 62,000 toadlets had been released into the wild. The toads became firmly established in Queensland, increasing exponentially in number and extending their range into the Northern Territory and New South Wales. Recently, the toads have made their way into Western Australia and one has even been found on the far western coast in Broome.
However, the toad was generally unsuccessful in reducing the targeted beetles, in part because the cane fields provided insufficient shelter for the predators during the day. Since its original introduction, the cane toad has had a particularly marked effect on Australian biodiversity.
The population of a number of native predatory reptiles has declined, such as the varanid lizards Varanus mertensi, V. mitchelli and V. panoptes, the land snakes Pseudechis australis and Acanthophis antarcticus, and the crocodile species Crocodylus johnstoni; in contrast, the population of the agamid lizard Amphibolurus gilberti—known to be a prey item of V. panoptes—has increased.
Caribbean:
The cane toad was introduced to various Caribbean islands to counter a number of pests that were infesting local crops. While it was able to establish itself on some islands, such as Barbados, Jamaica, and Puerto Rico, other introductions, such as in Cuba before 1900 and in 1946, and on the islands of Dominica and Grand Cayman, were unsuccessful.
The earliest recorded introductions were to Barbados and Martinique. The Barbados introductions were focused on the biological control of pests that were damaging the sugarcane crops, and while the toads became abundant, they have not been as successful in controlling the pests as in Australia.
The toad was introduced to Martinique from French Guiana before 1944 and became established. Today, they reduce the mosquito and mole cricket populations. A third introduction to the region occurred in 1884, when toads appeared in Jamaica, reportedly imported from Barbados to help control the rodent population. While they had no significant effect on the rats, they nevertheless became well established.
Other introductions include the release on Antigua—possibly before 1916, although there are suggestions that this initial population may have died out by 1934 and been reintroduced at a later date—and Montserrat, which saw an introduction before 1879 that led to the establishment of a solid population, which was apparently sufficient to survive the Soufrière Hills volcano eruption in 1995.
In 1920, the cane toad was introduced into Puerto Rico to control the populations of white-grub (Phyllophaga spp.), a sugarcane pest. Before this, the pests were manually collected by humans, so the introduction of the toad eliminated labor costs. A second group of toads was imported in 1923, and by 1932 the cane toad was well established.
The population of white-grubs dramatically decreased, and this was attributed to the cane toad at the annual meeting of the International Sugar Cane Technologists in Puerto Rico. However, there may have been other factors.
The six-year period after 1931—when the cane toad was most prolific, and the white-grub saw dramatic decline—saw the highest ever rainfall for Puerto Rico. Nevertheless, the assumption was that the cane toad controlled the white-grub; this view was reinforced by a Nature article titled “Toads save sugar crop”, and this led to large-scale introductions throughout many parts of the Pacific.
More recently, the cane toad has been spotted in Carriacou and Dominica, the latter appearance occurring in spite of the failure of the earlier introductions
The Philippines:
The cane toad was first introduced deliberately into the Philippines in 1930 as a biological control agent of pests in sugarcane plantations. This was done after the ‘success’ of the experimental introductions into Puerto Rico.
It subsequently became the most ubiquitous amphibian in the islands. It still retains the common name of kamprag in the Visayan languages, a bastardization of ‘American frog’, referring to its origins. It is also commonly known as ‘bullfrog’ in Philippine English.
Fiji:
The cane toad was introduced into Fiji to combat insects that infested sugarcane plantations. The introduction of the cane toad to the region was first suggested in 1933, following the successes in Puerto Rico and Hawaii. After considering the possible side effects, the national government of Fiji decided to release the toad in 1953, and 67 specimens were subsequently imported from Hawaii.
Once the toads were established, a 1963 study concluded that as the toad’s diet included both harmful and beneficial invertebrates, it was considered “economically neutral”. Today the cane toad can be found on all major islands in Fiji, although they tend to be smaller than their counterparts in other regions.[81]
New Guinea:
The cane toad was successfully introduced into New Guinea to control hawk moth larvae that were eating sweet potato crops. The first release occurred in 1937 using toads imported from Hawaii, with a second release the same year using specimens from the Australian mainland. Evidence suggests there was a third release in 1938, consisting of toads that were being used for human pregnancy tests—many species of toad were found to be effective for this task, and were employed for approximately 20 years after the discovery was announced in 1948.
Initial reports argued that the toads were effective in reducing the incidence of cutworm and it was suggested that sweet potato yields were improving. As a result, these first releases were followed by further distributions across much of the region, although their effectiveness on other crops, such as cabbages, has been questioned—when the toads were released at Wau, the cabbages provided insufficient shelter and the toads rapidly left the immediate area for the superior shelter offered by the forest.
A similar situation had previously arisen in the Australian cane fields, but this experience was either unknown or ignored in New Guinea. The cane toad has since become abundant in rural and urban areas.
United States:
The cane toad naturally exists in southern Texas, but attempts (both deliberate and accidental) have been made to introduce the species to other parts of the country. These include introductions to the mainland state of Florida and to the islands of Hawaii, as well as largely unsuccessful introductions to Louisiana.
Initial releases into Florida failed. Attempted introductions before 1936 and 1944, made with the objective of controlling sugarcane pests, were unsuccessful as the toads failed to proliferate. Later attempts failed in the same way.
However, the toad gained a foothold in the state after an accidental release by an importer at Miami International Airport in 1957, and deliberate releases by animal dealers in 1963 and 1964 established the toad in other parts of Florida.
Today, the cane toad is well established in the state, from the Florida Keys to north of Tampa, and they are gradually extending further northward. In Florida, the toad is a regarded as a threat to both native species and to pets, so much so that the Florida Fish and Wildlife Conservation Commission recommends that residents euthanize them.
Around 150 cane toads were introduced to Oahu in Hawaii in 1932, and the population swelled to 105,517 after 17 months. The toads were sent to the other islands, and more than 100,000 toads were distributed by July 1934; eventually over 600,000 were transported.
Uses:
Other than the previously mentioned use as a biological control for pests, the cane toad has been employed in a number of commercial and non-commercial applications. Traditionally, within the toad’s natural range in South America, the Embera-Wounaan would “milk” the toads for their toxin, which was then employed as an arrow poison.
There are also suggestions that the toxins may have been used as an entheogen by the Olmec people. The toad has been hunted as a food source in parts of Peru, and eaten after the removal of the skin and parotoid glands. More recently, the toad’s toxins have been used in a number of new ways: bufotenin has been used in Japan as an aphrodisiac and a hair restorer, and in cardiac surgery in China to lower the heart rates of patients.
Other modern applications of the cane toad include pregnancy testing, as pets, laboratory research, and the production of leather goods. Pregnancy testing was conducted in the mid-20th century by injecting urine from a woman into a male toad’s lymph sacs, and if spermatozoa appeared in the toad’s urine, the patient was deemed to be pregnant.
The tests using toads were faster than those employing mammals: toads were easier to raise, and, although the initial 1948 discovery employed Bufo arenarum for the tests, it soon became clear that a variety of anuran species were suitable, including the cane toad. As a result, toads were employed in this task for approximately 20 years.
As a laboratory animal, the cane toad is regarded as ideal; they are plentiful, and easy and inexpensive to maintain and handle. The use of the cane toad in experiments started in 1950s, and by the end of 1960s, large numbers were being collected and exported to high schools and universities.
Since then, a number of Australian states have introduced or tightened importation regulations. Even dead toads have value. Cane toad skin has been made into leather and novelty items; stuffed cane toads, posed and accessorised, have found a home in the tourist market, and attempts have been made to produce fertilizer from their bodies.
Information Sourced From:
