Females of this large bodied species can attain snout-vent lengths of over 225 mm, though most adults range from 85 to 150 mm. Adult males are yellowish-brown in color, with the yellow being most pronounced along the sides and the throat. Females and immature males have irregular brown blotches on their dorsal surface. The skin of both sexes is covered by irregularly scattered warts. In sexually active males these warts bear horny spicules. The parotoids are relatively large and often triangular and swollen in appearance. Cranial ridges are well developed. The tympanum is distinct, and the interorbital is concave. The webbing is poorly developed. The nuptial pads in the males are dark on the first 3 fingers (Easteal 1963).
 
Rick Speare has compiled a bibliography on this species up until 1991: Cane toad.
Karyotype: This species has a diploid chromosome (2n) with 5 large pairs and 6 small ones, which makes 22 chromosomes in total (Cole, Lowe, and Wright 1968).

A Spanish-language species account can be found at this website of Instituto Nacional de Biodiversidad (INBio).

The non-native marine toad, Bufo marinus, is the largest of Florida's frogs and toads. It has a stout body and short legs, with the digits of the forelimbs lacking webbing and those of the hind limbs being webbed. The skin is rough and warty. Skin ranges in color from gray to tan to red-brown, dark brown, olive to dull green, to black above, and cream-colored and often flecked with brown or black on the belly. The tympani (ear membranes) are one-half to two-thirds the diameter of the eyes (Ashton and Ashton 1988)The most distinguishing feature (other than size) is the presence of two large parotid glands, located at the shoulder behind each eye. These are venom glands capable of producing toxic milky secretions when squeezed. Smaller venom glands ('warts') are distributed all over the surface of the skin (Conant and Collins 1991, Gautherot 2000).Tadpoles are jet black dorsally and silvery white with black spots ventrally (Ashton and Ashton 1988).The vocalization of B. marinus is a slow, low-pitched trill and larger males usually have deeper calls (Somma 2004).

This species ranges from southern Texas, USA, through tropical Mexico and Central America to northern South America (central Brazil and Amazonian Peru and northern parts of Amazonian Bolivia, Colombia, Venezuela [including Margarita Island] and the Guianas, throughout Trinidad and Tobago). It is introduced in southern Florida, Puerto Rico (introduced in the 1920s), St Croix, St Thomas, Hawaii (introduced from Puerto Rico in 1932, now common on all main islands), Jamaica (including Cabarita Island) (introduced from Barbados in 1844, common throughout island in lowlands), the U.S. Virgin Islands, Hispaniola (Dominican Republic and Haiti), St Kitts, Nevis, Antigua, Montserrat, Guadeloupe, the Grenadines, Martinique, St Lucia, St Vincent, Barbados, Aruba, Grenada, Guam (McCoid 1993), Saipan (Wiles and Guerrero 1996), and many other tropical and subtropical localities (Schwartz and Henderson 1988). It is also an invasive and introduced species in much of the lowlands of Papua New Guinea, the Admiralty and Bismarck Islands and the Solomon Islands. It was introduced to Australia in 1935, to north tropical Queensland to control sugar cane pests (which it failed to do). Now the southern limit of its distribution is near Coffs Harbour in northeastern New South Wales, and its range extends through most of Queensland and into the Northern Territory to Kakadu National Park (first recorded at Koolpin Gorge, 24 June 2002 and Twin Falls, 10 June 2002). It is also introduced and now widespread in the Philippines. It is found on most of the major islands. It was introduced into Japan first from Hawaii to Taiwan, Province of China, and then from Taiwan through Daito Islands (1930) to Ishigaki Island (1978). The population of Bonin Island was introduced from Guam, which in itself had the species introduced in 1937 (Christy et al. 2007). It is also found on Hatomajima. It occurs from sea level up to 3,000 m asl.

The natural range of Rhinella marina is from the Rio Grande Valley of Texas south to the Central Amazon and southeastern Peru. This toad has been introduced into the Caribbean Islands, South Florida (Key West and Stock islands, Tampa Bay, Hillsborough, Dade and Broward counties), the Hawaiian islands, and Australia's east coast (East Queensland and Coastal New South Wales). Rhinella marina has been called one of the 100 worst invasive species worldwide by the Invasive Species Specialist Group.

Biogeographic Regions: nearctic (Introduced , Native ); neotropical (Introduced , Native ); australian (Introduced ); oceanic islands (Introduced )

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Southern Texas to South America. Introduced in southern Florida, Puerto Rico (introduced in 1920s), St. Croix, St. Thomas, Hawaii (introduced from Puerto Rico in 1932, now common on all main islands), Jamaica (including Cabarita Island) (introduced from Barbados in 1844, common throughout island in lowlands), Lesser Antilles, Bermuda, Guam (McCoid 1993), Saipan (Wiles and Guerrero 1996), and many other tropical and subtropical localities (Schwartz and Henderson 1988). Elevational range: sea level to about 2900 ft (880 m) (Schwartz and Henderson 1991).

Naturally occurring populations are found from the southern tip of Texas and northwestern Mexico to central Brazil. Introduced populations have been established in the Caribbean and Pacific regions. Upper altitudinal limits vary with latitude, from 500 m in Sinaloa, Mexico to 1600 m in Venezuela (Easteal 1963). Bufo marinus was introduced to Northern Queensland, Australia in 1929 and has since spread throughout much of the continent (Lampo and De Leo 1998).

This invasive species is found in all major faunal regions in the Philippines as well as many small island groups and islolated islets.

This species has been introduced to the Philippines and has invaded all major and many smaller islands throughout the country.

Countries

Native to: Belize, Bolivia, Brazil, Colombia, Costa Rica, Ecuador, El Salvador, French Guiana, Guatemala, Guyana, Honduras, Mexico, Nicaragua, Panama, Peru, Suriname, Trinidad and Tobago, United States, Venezuela   Introduced in: Antigua and Barbuda, Aruba, Australia, Barbados, Dominican Republic, Grenada, Guadeloupe, Guam, Haiti, Jamaica, Japan, Martinique, Montserrat, Northern Mariana Islands, Papua New Guinea, Philippines, Puerto Rico, Saint Kitts and Nevis, Saint Lucia, Saint Vincent and the Grenadines, Solomon Islands, Taiwan, United States (Florida and Hawaii), Virgin Islands

Bufo marinus is a highly adaptable invader and where it occurs in Florida it is typically found in agricultural and urbanized areas.The native range of B. marinus extends from northern South America, through Central America and Mexico, and up into southernmost Texas (Conant and Collins 1991, Somma 2004).The species is established in south Florida and around Tampa on the Gulf coast, and they are also found on Stock Island and Key West (USGS/SEARMI). These populations are probably derived from intentional introductions as well as accidental introductions in agricultural products and from escapes of pets from homes and from the pet trade (Somma 2004). Collection records indicate Bufo marinus occurs in at least three of six India River Lagoon watershed counties (Palm Beach, Martin, Indian River, probably St. Lucie as well). It appears to be widely established in Palm Beach and Martin counties. Smaller populations of B. marinus pesist elsewhere in isolated pockets as, for example, an established population reported in Vero Beach near Dodgertown in 2002.

occurs (regularly, as a native taxon) in multiple nations

United States

Origin: Native

Regularity: Regularly occurring

Currently: Present

Confidence: Confident

Type of Residency: Year-round

Rhinella marina has a grey olive brown dorsal skin with many warts ending in dark brown caps. The ventral skin tends to be a whitish yellow with dark brown speckles or mottles and is granular. Rhinella marina possesses huge paratoid glands stretching from the anterior side of the tympanum to halfway down the back. A high bony ridge meets at the snout between the nostrils. Rhinella marina, like other nocturnal species, has horizontal pupils. Rhinella marina can reach a maximum length of 238 millimeters, although generally is approximately 150 to 175 millimeters.

Range length: 150 to 238 mm.

Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry ; poisonous

Sexual Dimorphism: sexes alike

Average mass: 106.25 g.

Average basal metabolic rate: 0.0303 W.

Length: 22 cm

Bufo marinus in Florida can reach sizes of around 10-15 cm (and up to nearly 24 cm elsewhere) and female toads can weigh up to 2.5 kg (Behler 1979, Somma 2004).

Adult

Species description based on Ibanez et al (1999) and Savage (2002).  A very large toad (males to 145 mm, females to 175 mm).

Dorsal

Dorsal coloration varies from yellowish brown to dark brown. The dorsum is mottled in females and uniform in males. The paratoid glands are very large.

Eye

The iris is brown.

Extremities

The hands and feet are mostly unwebbed.

Holotype for Rhinella marina
Collection: Smithsonian Institution, National Museum of Natural History, Department of Vertebrate Zoology, Division of Amphibians & Reptiles
Sex/Stage: Female;
Preparation: Ethanol
Year Collected: 1940
Locality: La Esperanza, Chiapas, Mexico

The size of the marine toad and the presence of the large parotid glands and webbed hind digits make this species easy to distinguish from other Florida frogs and toads.

Habitat and Ecology

Systems

• Terrestrial
• Freshwater

Rhinella marina is a tropical species that prefers forested areas with semi-permanent water nearby (Cogger 1983).

Habitat Regions: tropical ; terrestrial

Terrestrial Biomes: forest ; rainforest

Comments: Humid areas with adequate cover, including cane fields, savanna, open forest, well-watered yards and gardens. Can be found by day beneath fallen trees, loose boards, matted coconut leaves, and similar cover (Lynn 1940). Flexible in breeding site (Evans et al. 1996, Copeia 1996:904-912); eggs and larvae develop in slow or still shallow waters of ponds, ditches, temporary pools, reservoirs, canals, and streams. May sometimes breed in slightly brackish water in Hawaii. Larvae are tolerant of high temperatures.

Although this species is exceptionally common in disturbed habitats, agriculatural lands (including rice fields), and residential habitat, observations have also been made of this species in distrubed, lowland forest.

Habitat

Rhinella marina inhabits both humid and dry environments, as long as there is some vegetation available for cover (to 3000 m.). It is typically more abundant in disturbed habitats and rare in pristine forest (Ibanez et al 1999).

Non-Migrant: Yes. At least some populations of this species do not make significant seasonal migrations. Juvenile dispersal is not considered a migration.

Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).

Locally Migrant: No. No populations of this species make annual migrations of over 200 km.

Rhinella marina forages primarily nocturnally in mature forests and roadways. It feeds on ants, beetles, and earwigs in southern Florida, but has been found with dragonflies, grasshoppers, truebugs, crustaceans, gastropods, plant matter and even dog and cat food in their stomachs (Krakauer 1968).

Animal Foods: insects; terrestrial non-insect arthropods

Primary Diet: carnivore (Insectivore , Eats non-insect arthropods)

Comments: Metamorphosed toads eat mainly various terrestrial invertebrates, especially ants and beetles; sometimes small vertebrates; also may eat inanimate foods such as processed pet food and discarded food scraps (McCoid, 1994, Herpetol. Rev. 25:117-118). Larvae eat suspended matter, organic debris, algae, and plant tissue.

Marine toads are voracious predatory omnivores that consume not only insects and other arthropods but also molluscs, vegetation, and any other frogs or toads they encounter. In urbanized settings, they will consume cat or dog food if it is left out and they may also scavenge garbage (Alexander 1964, Cabrera et al. 1996, Somma 2004).Marine toads are primarily nocturnal and they often congregate around lights to take advantage of the insects that they attract.

None reported.Invasion History: Marine toads have been repeatedly introduced throughout the world as a potential biological control agent for crop-damaging insects, primarily those that damage sugarcane (Krakauer 1968, 1970). The most infamous introduction is the 1935 intentional release into the canefields of Queensland, Australia in an unsuccessful attempt to control the sugar pest the greyback cane beetle (Dermolepida albohirtum). The marine toads used in the Queensland introduction were from Hawaii where the species had been intentionally introduced just a few years earlier (McKeown 1996, Lever, 2001).The first attempts at intentional introduction of Bufo marinus into Florida occurred at approximately the same time as the Hawaii and Australia introductions. Specimens imported from Puerto Rico were released into Palm Beach County in 1936 but the species failed to become established on this occasion and in two subsequent attempts as well (Krakauer 1968).Marine toads finally did become established in Florida after an accidental release by an importer in 1955 from the Miami Airport (Krakauer 1968, Ashton and Ashton 1988). Additional intentional releases into south Florida in 1963 and 1964 facilitated establishment and subsequent explosive population growth. The species was recognized as a nuisance species requiring control as early as 1965 (Krakauer 1968, 1970). Potential to Compete With Natives: Marine toads likely compete with native species for food, living space and breeding sites and may have, in some parts of the world, been a the principal cause of local extirpation of some native amphibians (Krakauer 1968). Marine toads also eat other species of frogs and toads and practically any other suitably-sized animal they encounter. Possible Economic Consequences of Invasion: The defensive secretions produced by the parotids and other poison glands are highly toxic and are capable of killing dogs, cats, and other animals that bite into or attempt to consume them (USGS/SEARMI). Effects on native fauna are not fully known but are believed to be similar.The secretions are also capable of making humans seriously ill, and of causing serious skin and eye irritation Carmichael and Williams 1991, Conant and Collins 1991).Bufo marinus is listed by ISSG as as among "100 of the Worst" global invasive organisms, and authorities consider it to be the "most introduced amphibian in the world" (Behler 1979, Carmichael and Williams 1991).

Bufo marinus is prey of:
Buteo jamaicensis
Scolopendra alternans
Epilobocera situatifrons
Diptera
Secernentia nematodes

Based on studies in:
Puerto Rico, El Verde (Rainforest)

This list may not be complete but is based on published studies.

Bufo marinus preys on:
Hymenoptera
Isoptera
Coleoptera
non-insect arthropods
Arthropoda
Insecta

Based on studies in:
Puerto Rico, El Verde (Rainforest)

This list may not be complete but is based on published studies.

>1,000,000 individuals

Comments: Total adult population size likely exceeds 1,000,000.

Bufo marinus is considered to be abundant in Dade and in some areas of Monroe Counties, occurring in lesser numbers elsewhere in south Florida (USGS/SEARMI).

Very mobile. In Puerto Rico, moved as far as 165 m to water hole and back to activity center in same or next night; activity centers up to 862 sq m; 3-17 days between visits to water hole; water hole and damp surfaces used for rehydration (Carpenter and Gillingham 1987).

Dry-season dessication may be a major mortality factor.

Population density in seminatural habitats may be 50-150 adults and late-term juveniles per ha, with about 66% annual population turnover (Schwartz and Henderson 1991). Chernin (1979, MS thesis, Univ. Guam) reported densities as high as 225/ha in Guam.

Ecology

Rhinella marina nocturnal, and is commonly encountered on the ground in urban environments (Ibanez et al 1999).

Communication Channels: tactile ; acoustic ; chemical

Other Communication Modes: choruses

Perception Channels: tactile ; acoustic ; chemical

Call

A long, low trill (Ibanez et al 1999). The call can be heard from very far away (Ibanez et al 1999).

Comments: Mostly nocturnal, though often observed during daylight. Most active during warm, wet weather. Individuals may not be active every night.

The eggs hatch between forty-eight hours and one week. The tadpoles tend to be small and black and aggregate in dense numbers. Tadpoles metamorphose into small toadlets identical to the adults in forty-five to fifty-five days (Bureau of Rural Sciences 1998).

Development - Life Cycle: metamorphosis

Breeding season

Breeding occurs year-round (Ibanez et al 1999). Rhinella marina uses a wide variety of aquatic habitats for breeding, ranging from temporary pools to rivers and lakes (Ibanez et al 1999).

Egg

Small, black eggs are laid in strings in shallow water (Ibanez et al 1999).

Tadpole

The tadpoles are small and black (Ibanez et al 1999). The tadpoles often aggregate while feeding during the day (Hughey pers. obs.).

Rhinella marina is a relatively long-lived toad, reaching ages up to ten years (Cogger 1983).

Range lifespan

Status: wild: 10 (high) years.

Average lifespan

Sex: female

Status: captivity: 8.0 years.

Maximum longevity: 24.8 years (captivity) Observations: In non-tropical tempered zones this toads may take 2 years to reach reproductive maturity (http://amphibiaweb.org/).

Males congregate in temporary or permanent still or slow moving water and call for mates. More than one male may fertilize the eggs of a single female, and a particularly successful males may fertilize the eggs of multiple females in a breeding season.

Mating System: polygynandrous (promiscuous)

Rhinella marina is able to reproduce nearly year round. The females are able to lay eggs after their second year. Eggs are laid in long jelly-like strings on rocks, debris, or emergent vegetation; in excess of 30,000 eggs at a time. The eggs hatch in 2 to 7 days.

Breeding interval: These toads breed once yearly.

Range number of offspring: 30,000 (high) .

Range time to hatching: 2 to 7 days.

Key Reproductive Features: iteroparous ; seasonal breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (External ); oviparous

Once the eggs are fertilized and arrayed in the water, there is no further parental care.

Parental Investment: pre-fertilization (Provisioning)

Usually breeds after rains; capable of breeding any time of year in most areas. Eggs hatch in a few days. Larvae metamorphose in 1-3 months. Sexually mature generally in 1-2 years, possibly in as few as 6 months in some areas.

In Florida, Bufo marinus typically breeds in man-made habitats such as drainage canals and ditches, fish ponds, temporary pools and other shallow water bodies (Somma 2004). Breeding in Florida typically occurs during the wet season from early spring into the fall, and typically occurs during or just after rain events (Conant and Collins 1991).B. marinus exhibits high fecundity with large females capable of producing 20,000 eggs or more (Somma 2004).

Mate attraction in frogs and toads typically involves multiple males calling and females responding to these acoustic signals, often choosing which prospective male to approach based at least in part on differences among the calls of different males. Mating typically involves the male grasping the female in amplexus (a tight "embrace" in which the male mounts the female, wrapping his front legs around her). In most frogs and toads, including Cane Toads, fertilization is external, with males depositing sperm on eggs as they are laid. In many species, "satellite males" may also be present at breeding sites. A satellite male may remain silent, but rather than compete with other males to attract a female, he may instead intercept a female attracted by another male and attempt to force a mating by grasping her in amplexus and fertilizing her eggs.

Bruning et al. (2010) investigated the possibility that female Cane Toads may be able to affect the outcome of competition among males for the primary amplexus position by making it more or less difficult for particular aspiring mates to maintain amplexus. This would allow females to retain a greater degree of female mate choice. The authors suggest that female Cane Toads (and presumably some other species as well) have co-opted a common anti-predator strategy for this purpose. Frogs and toads often defend themselves against predators by inflating their body: the increased girth may deter predators by both increasing the apparent size of the animal and by rendering it too large to ingest (e.g., Williams et al. 2000). Bruning et al. carried out experiments in which male frogs were induced to clasp model females with adjustable balloons inserted inside them. The researchers then measured the force required to pull males off females inflated to varying degrees. They also carried out mating trials using live females that had had their ability to inflate eliminated by placing a catheter into the trachea, preventing the tracheal glottis from closing (which is necessary to keep the body inflated). The results reported by Bruning et al. indicate that inflated female toads are indeed more difficult for males to hold on to, and that the ability of a female in amplexus to inflate her body can facilitate takeovers by larger rival males. In females who were unable to inflate, a small male could maintain his amplectant position despite takeover attempts by larger rivals. Thus, a female toad’s ability to inflate her body can influence the body size of her eventual mate. Given that females may often benefit from mating with larger-than-average males (Davies and Halliday 1977), females might use their ability to inflate to make it easier for a rival male to dislodge a smaller male. This could explain why field studies typically find that larger males are able to dislodge smaller ones.

Egg strings may be free-floating or wrapped around submerged as well as surface material (Somma 2004). Eggs hatch into tadpoles at around three days and the tadpoles metamorphose to juvenile toads around 45-55 days later (Krakauer 1970, Ashton and Ashton 1988).

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 1
Species: 26
Species With Barcodes: 1

Barcode of Life Data Systems (BOLDS) Stats
Public Records: 0
Species: 4
Species With Barcodes: 1

In their native range cane toads are common, and not considered in need of special conservation efforts. Cane toads are considered one of the world's top 100 most widely-introduced species. Where they have been introduced they are considered pests, and targets of extermination efforts.

US Federal List: no special status

CITES: no special status

IUCN Red List of Threatened Species: least concern

United States

Rounded National Status Rank: N2 - Imperiled

Rounded Global Status Rank: G5 - Secure

Intrinsic Vulnerability: Moderately vulnerable

Environmental Specificity: Moderate to broad.

Population

Population Trend

The mating call is long and has 12 notes/sec. The dominant frequencies are .35 and .7 kHz without frequency modulation to clear harmonics ((Cole et.al. 1968).

Potential Impacts: This toad is highly toxic, secretions from the skin serve as a natural defense against predators. The toxin is stored in the ovum, not the jelly coat. The toxicity of cane toads shifts rapidly during the course of their lifetime. Toad eggs are extremely toxic, while later-stage tadpoles were less toxic. Animals that bite these toads are often seriously affected, many are killed. Domestic dogs and cats often are killed by the toxins. Native wild animals are also affected especially in places where the toads are introduced (especially in places like Australia and in Florida, USA). Marine toads may compete with and prey upon native amphibians (Rabor in Krakauer, 1968).

As an invasive species, cane toads have the potential to bring harmful viral pathogens to native fauna. Scientists found that cane toads carried three of the 14 protozoan species of neotropical origin. Cane toads in Australia also contain nematode lungworm, a parasite endemic to the Americas. While these pathogens and parasites could potentially infect native frog species, observations show that infection has not spread to other native species.

In addition to the direct impacts that cane toads may have on native fauna, the cane toad may also have indirect impacts on food webs and population dynamics. For example, predation on dung beetles by cane toads could reduce dung breakdown rates, affecting many aspects of ecosystem function. Toad invasion can massively reduce the population of predators such as varanid lizards, elapid snakes, freshwater crocodiles, and northern quolls that die from consuming cane toad toxins.

Metamorphosis occurs in tadpoles between 14 and 28 days after hatching, depending on the water temperature. Eggs hatched late in the dry season will metamorphose before the late wet season, when food is most readily available and moisture stress is reduced (Lampo and De Leo 1998). After metamorphosis these toads leave the water and seek diurnal refuges to avoid dehydration and predation. B. marinus uses hollow trees for shelter during the dry season and dense vegetation during the wet season in addition to rock crevices which are used throughout the year (Seebacher and Alford 1999). These toads show more nocturnal activity and travel greater distances per night in Australia than in South America (Seebacher and Alford 1999).

Introduced to many localities in the first half of the 20th century as a means to control sugar cane pests, these toads have undergone a population explosion. They have established widespread ranges in these non-native areas and attain higher densities in Australia than they do in their native range (Lampo and De Leo 1998). This has caused much concern about the effects of B. marinus on native anuran species. The eggs and hatchlings of B. marinus are toxic to many native predators in Australia. The predatory frog species Limnodynastes ornatus showed decreased survivorship where it co-occurred with B. marinus. However Limnodynastes rutella, which is preyed upon by L. ornatus, showed increased survival rates (Crossland 2000). Bufo marinus can inhabit open land near human habitations and sugarcane fields.

B. marinus is an opportunistic feeder, and readily feeds upon land snails as well as centipedes, cockroaches, beetles, grasshoppers, ants, and small field mice. Stomach samples of this species in particular areas of the world show that terrestrial gastropod prey can comprise over 40% of the stomach contents (Hinckley 1963; Bailey 1976; Grant 1996). In laboratory trials under wet conditions, it was found that B. marinus readily consumes a range of camaenid snail species. This makes it unique from other anurans that typically do not prey upon molluscs. While some scientists have proposed that B. marinus consumes vertebrates (e.g., ground-nesting birds such as bee-eaters), this has been found to be very rare. In follow-up studies, cane toads avoided (rather than selected) birds and their eggs as prey (Merops ornatus: Boland 2004).

B. marinus is primarily diurnal in activity, and lacks defense against ant species that are immune to toad toxins. Freshwater crayfish, adult dytiscid diving beetles, dragonfly larvae, and mosquitoes are among other native invertebrates that feed upon the cane toad without ill effects. However, leeches and aquatic snails that feed on larval or adult toads often die from the toxins that are consumed. It should be noted that other invertebrates vary in their susceptibility to toads. Some dytiscid diving beetle larvae can consume hatchlings and tadpoles while others die. Belastomatid giant water bugs can consume some developmental stages of tadpoles without ill-effect, but not others.

Cane toads can serve as an additional food source to vertebrates. Snakes like the keelback (Tropidonophis mairii) and slatey-grey snakes (Stegonotus cucullatus) can consume the cane toads without dying, but keelbacks do show ill-effects. When given a choice, keelback snakes prefer native frogs to cane toads (Llewelyn et al. 2009b). Similarly, raptors consume road-killed toads, but preferentially select native frogs when given a choice. Water rats and introduced black rats frequently consume cane toads.

Most species of Australian freshwater fish often mouth and spit out cane toad early life stages without apparent ill effects. For the fly-specked hardyhead (Craterocephalus stercusmuscarum), the banded and spangled grunters (Amniataba percoides and Leiopotherapon unicolor respectively), the purple-spotted gudgeon (Morgurnda adspersa), glassfish (Family Ambassidae), western rainbowfish (Melanotaenia australis), and black catfish (Neosilurus ater), consuming cane toad eggs or tadpoles are toxic. However, most fish avoid cane toad early life stages because they can detect their noxiousness. For most fish, toad eggs are likely to be more lethal than toad tadpoles.

In 1975, Covacevich and Archer reported that saltwater crocodiles (Crocodylus porosus) could ingest cane toads without ill-effect, while freshwater crocodiles (Crocodylus johnstoni) died after mouthing or ingesting cane toads (Begg et al. 2000). In 1990, Freeland found that C. johnstoni actively hunts and ingests cane toads. It was later reported in 2009 that the deaths of some freshwater crocodiles in the Daly River were due to toad ingestion. A population-level impact study found 34 dead freshwater crocodiles in the Victoria River caused by cane toad ingestion (Letnic et al., 2008). Evidence included a wave of crocodile deaths moving upriver and coinciding with the areas in which cane toads were invading, as well as toad remains found in the stomachs of some of the dead crocodiles.

Turtles also vary in their tolerance for cane toad toxicity. In some cases, turtles ingest toads without ill effect, while other predation attempts by the same species result in fatality. The long-neck turtle (Chelodina sp.) ate a dead cane toad without ill effect, while the saw-shelled turtles (Elseya latisternum) and Krefft's river turtles (Emydura krefftii) consumed toad tadpoles and were also unaffected. In a study by Kruger, long-necked turtles (Chelodina rugosa) seized and spit out toad tadpoles and survived, yet died after consumption of toad eggs.

The area of Australia invaded by cane toads contains high densities of lizards belonging to several phylogenetic lineages. The impact of toads across the lineages is highly nonrandom. Fatal poisoning occurs in three lineages: the Varanidae (goannas), the Scincidae (skinks), and the Agamidae (dragons). Varanids often grow to large body sizes and are therefore more likely to attack a large cane toad more readily than a lizard from most other lineages. Varanids often die after ingesting or mouthing cane toads. Most species of scincid lizards have a relatively small adult body size. Due to their small body size, most Scincid lizards are unlikely to be at risk from consuming a cane toad large enough to kill them. However, some species such as the bluetongue skink (Tiliqua scincoides intermedia) readily consume small toads and die as a result.

Snake species at risk from cane toads are frog-eating species that cannot tolerate toad toxins, can swallow toads large enough to be fatal, and whose geographic distribution overlaps with that of the cane toad. Using this criteria, 49 snake species were found to be potentially at risk from toad invasion. The toad invasion is a potential threat to 70% of the Australian colubrid snakes, 40% of the pythons, and 41% of the elapids. Nine of the species that were deemed "at risk" are currently recognized as threatened species on a federal or state level. Recent work on the feeding patterns of snakes in captivity have shown that species that were previously identified as potentially at risk species were reluctant to take cane toads as prey, or immediately rejected the cane toad after striking it. Colubrids and pythons appear to be less at risk than the elapid snake species, with high mortality rates in death adders (Acanthophis praelongus), black whip snakes (Demansia papuensis), and king brown snakes (Pseudechis australis)(M. Greenlees et al. unpubl. data in Shine 2006).

In 1975, Covacevich and Archer reported that some crows (Corvus sp.) and kookaburras (Dacelo novaeguineae) died after mouthing cane toads, while other individuals of the same species consumed young or road-killed toads without showing any ill effects. At least seven native bird species can eat toads successfully. Reasons for this tolerance may be because they eat only non-toxic parts of the toad or because they are immune to the toxins. In 1997, Dorfman predicted that 76 species in the Kakadu National Park were potentially under threat from cane toads. However, more recent studies by Beckmann and Shine in 2009 have concluded that cane toads appear to have minimal impact on Australian birds. The ability to survive toad invasion may be due to a widespread physiological tolerance of bufotoxins, perhaps reflecting close genetic ties between Australian birds and taxa in Asia, where many bufonid species are similar in toxicity to the cane toad.

In 2004, Webb and Glanznig listed nine species of native mammals and two species of introduced mammals as potentially at risk from cane toad ingestion. Due to previous reports of domestic dogs dying from mouthing cane toads, dingos may also be at risk. Feral cats and pigs also may be negatively affected by cane toads. In captivity, native rodents (Melomys burtoni, Rattus colletti, R. tunneyi) readily killed and consumed small toads, but did not appear to suffer any ill effects. Other rodents (Must domesticus, Pseudomys nanus, Zyzomys argurus) did not attack cane toads as prey at all. Small dasyurid marsupial species, like planigales (Planigale ingrami, P. maculata) and dunnarts (Sminthopsis virginiae) initially attacked toads, became ill as a result, and were later reluctant to attack toads. Relatively few of these dasyurids died as a result of attempting to ingest toads. The species of mammal that is most often a victim of toad invasion is the northern quoll, Dasyurus hallucatus. Lethal ingestion of cane toads is responsible for the local extinction of northern quoll populations in the Mary River region of Kakadu National Park. One study showed that only four of 14 quolls that died from toad ingestion, suggesting that perhaps other factors may be playing a role in quoll extinction. However, more recent studies show that seven out of eight quoll deaths resulted from ingestion of cane toads. In addition, quolls have been killed by toads in areas where very few toads were spotted, suggesting that even in low toad density areas, quolls are still threatened.

Cane toad impacts are affected by attributes of toad biology. Cane toads have a multiphasic life history. Eggs and tadpoles reside in waterbodies, metamorphs are only found in riparian areas, and larger juveniles and adults occupy large areas of drier landscape. In addition, the types and amounts of toxins present in toads vary throughout their lifetime. One specific feature of the cane toad is that their highly toxic eggs are coated in a non-toxic jelly, fooling aquatic predators into consuming them when they would otherwise be able to detect bufotoxins in their prey (Greenlees and Shine 2010).

There also seems to be competitive interactions between cane toads and three species of native tree frogs around waterholes in the Gulf of Carpentaria: Litora pallida, L. rothii, and L. rubella. Evidence suggests that cane toads are likely to have a more adverse impact on larger terrestrial frogs like Cyclorana australis and Limnodynastes convexiusculus. These impacts may be caused by direct behavioral interference rather than competition for food. In a study done in 2009 by Pizzatto and Shine, nine out of ten native frog species avoided sites scented by cane toad chemical cues (all except Litoria rubella), and in 2007, Greenlees et al. found that the presence of cane toads reduced the nocturnal activity levels of the native frog Cyclorana australis. Sexual harassment of female frogs by male toads is also known to occur between native and introduced taxa in other phylogenetic linages (e.g. Valero et al. 2008). In addition to competition involving native anurans, other vertebrate species may also compete with toads for limited resources. In 2004, Boland suggested that cane toads may compete with the nesting burrows of bee-eaters, Merops ornatus.

Cane toads were first introduced into northern Australia in 1936, and have rapidly spread across 1.3 million square kilometers of northern and eastern Australia since (Urban et al., 2007). In northern Australia, toad population expansion has accelerated steadily, from approximately 10 to 55 kilometers per year. On the invasion front, toads move far distances (up to 1.8 km per night), and mostly move in straight lines, actively using cleared areas such as roads as dispersal corridors (Brown et al., 2006; Phillips et al., 2007). This expansion behavior can be compared with toads from older populations. Currently, invasioni front individuals move more often, travel farther per move, and tend to move in straighter lines. However, environmental correlates do not adequately explain these changes (Urban et al., 2008). In order to test whether these differences in behavior resulted from evolution or just plasticity associated with new toad environments, an experiment was created. The dispersal rates of parent populations during the cane toads invasive history was measured and compared to dispersal rates of the offspring. Through this collection method, researchers hoped to minimize environmental effects on on dispersal ability and estimate the heritability of dispersal. 184 toads were radiotracked over two seasons. Toads with larger bodies consistently moved farther than toads with normal or smaller body sizes. The breeding cohort resulted in high levels of variance in daily dispersal of the adult toads. This suggests that differences in birth date can have large influences in dispersal.The estimate of mean within-population genetic variance was large and suggested a narrow sense heritability of 0.24. In addition, there was a log mean daily displacement in this species with a large 95% interval of 0.02-0.72. Thus, there is evidence to suggest that there does seem to be a heritable variance within toad populations for dispersal. This selection on disperse could produce evolutionary change.

Female anurans have been shown to be the choosier sex, selecting mates that show good resource defense techniques or attractive male displays. However, the only way that females can exercise mate choice is by approaching a male with an attractive call or mating site. When a female approaches such sites, she may be intercepted by a "satellite" male that attempts to mate with the female by grasping her in amplexus (Wells 2007). This is particularly common in areas of high density. In a recent study conducted with B. marinus, it was found that perhaps females are not just passive participants in the mating process, but rather have a mechanism of exercising control. Evolutionarily, frogs and toads are able to protect themselves from predators by inflating their bodies. This increased girth may deter predators who may be threatened by an anuran that is too large to ingest. Similarly, female anurans frequently inflate their bodies when being amplexed from males. In this sense, the female cane toads could facilitate male-male competition by reducing the ability of undesirable mates to grasp onto her. In females who were unable to inflate their bodies, the small "satellite" male was aable to grasp onto the female despite takeover attempts by larger rivals. Body size of mates is a factor in female mate choice because fertilization success is highest when the males and females are close in size. Since females are the larger size, choosing a larger male increases the fitness of their offspring. Larger males are often able to displace smaller males, but smaller males rarely displace larger rivals. However, smaller males can resist takeover attempts if the female does not inflate her body. Therefore, this study shows that takeovers by larger males can show female and male tactics in sexual selection.

Major Threats

Comments: No significant threats.

According to the Global Amphibian Assessment (GAA), Bufo marinus is of least concern with regards to extinction and its population is actually increasing. There are currently no significant threats to this species. Some animals that have been introduced to Puerto Rico carry salmonella, putting species that consume them at risk. In Bermuda, survival and development of tadpoles are being negatively affected due to contaminants in ponds and the transfer of accumulated contaminants (Bacon et al. 2006).

Conservation Actions

This toad is considered the most widely-introduced amphibian species in the world. People have tried to use it to control insects such as the greybacked cane beetle, Lepidoderma albohirtum which threatened sugar cane production. However, there is no evidence that it has controlled any pest in Australia and it is now considered a pest species itself in its introduced range of Australia and on Pacific and Caribbean Islands. It preys on and outcompetes native amphibians and also causes predator declines, since these predators have no natural immunity to the bufotoxin it secretes. (Bureau of Rural Sciences 1998, Aguirre and Poss 1999).

Negative Impacts: injures humans (poisonous ); household pest

Comments: Introduced in many areas in effort to reduce populations of agricultural pests (insects, white sugar cane grub in Puerto Rico).

Species Impact: As an introduced species, B. marinus can negatively impact native species and predator assemblages through competition, predation, and toxicity of its eggs or metamorphosed individuals(Punzo and Lindstrom 2001, Phillips et al. 2003). Phillips et al. (2003) concluded that introduced B. marinus potentially threaten populations of approximately 30 percent of terrestrial Australian snake species.

Humans are affected by the toxic skin secretions. Symptoms include irritation of the skin and burning of the eyes (Wright and Wright, 1949; Krakauer, 1968, 1970; Behler, 1979; Carmichael and Williams, 1991; Conant and Collins, 1991).

Marine toads have probably been introduced more widely than any other amphibian in the world (Behler, 1979; Carmichael and Williams, 1991). They have been introduced as a control agent for insects that damage sugarcane (Riemer, 1959; Krakauer, 1968; King, 1970), however, since they are nocturnal and many sugarcane pests are diurnal, they are not effective biocontrol agents. For information on introductions into Australia, please see Cane toad-Australia .

Human perceptions of the cane toad are largely negative, with many fearing its size, appearance, and potential invasive impact on Australian communities. Between 1986 and 1996, the state and federal government spent more than $9,500,000 (Shine et al. 2006) and enormous efforts by volunteers to control local toad populations by collection. However, these negative community perceptions of invasive species impacts are often in error. In actuality, the direct impact of cane toads falls heavily on a small number of native taxa, not a wide spectrum of native fauna. Others suggest a more direct effect on humans by claiming that toads are poisoning waterholes with their toxins and are even leading to drug abuse for humans that become addicted to licking the toads or smoking their dried skins (Clarke et al. 2009). However, there are no data that actually supports these claims.

Recently, humans have thought that a native predator, the meat ant (genus Iridomyrmex), could control the invasive cane toad populations. In an experimental setting, 98% of metamorph toads encountered at least one predator ant species in a high density ant environment, while 87% of metamorph toads encountered at least one predator ant species in a low density ant environment. Most of these toads were attacked, with 82.5% killed at high density and 51% killed at low density. From these data, it appears as though high ant density is more effective at controlling cane toad populations. There are multiple reasons to explain why this may have occurred. First, higher density inevitably leads to more encounters. In addition, at higher ant densities, ants are more likely to swarm onto a prey item. Lastly, higher ant densities increase the body-size threshold at which metamorph toads shift their defense mechanism from the active escape tactic to crypsis. As a result of this higher ant density, more toads of a wider range of body sizes are killed.

In the field, smaller metamorph deaths were most commonly observed. This may be because small metamorphs have a less effective response to ant attack and are also more vulnerable to disease and parasites, such as lungworm (Kelehear 2007), as well as dessication (Child et al. 2008). In addition, the low level of toxins in metamorphs make them even more susceptible to predator attack.

However, it should be noted that meat ants alone are not entirely feasible for controlling cane toad populations. Meat ants are only effective at killing metamorph toads, and may be less effective during the wet-season recruitment events. Increased ant densities might even serve as a food source for adult cane toads. Many are also cautious because using biocontrol in other instances have often vastly negatively affected ecosystems in ways that could not have been predicted. In this instance, the predator is already a native species and is simply being redirected to areas with high populations of cane toads. But reduced or increased populations of ants in certain areas may still affect native fauna, and meat ants can still competitively exclude ecologically similar ant species.