Cane Toad Facts

The cane toad (Rhinella marina) is a large, terrestrial toad that gets its common name for its role in fighting against the cane beetle (Dermolepida albohirtum). While useful for pest control, the highly adaptable toad has become a problematic invasive species outside its natural range. Like other members of the family Bufonidae, the cane toad secretes a potent toxin, which acts as a hallucinogen and cardiotoxin.

Description

The cane toad is the largest toad in the world. Typically, it reaches a length between 4 and 6 inches, although some specimens may exceed 9 inches. Mature females are longer than males. The average weight of an adult toad is 2.9 pounds. Cane toads have warty, dry skin in a variety of patterns and colors, including yellow, red, olive, gray, or brown. The underside of the skin is cream-colored and may feature darker blotches. Juveniles have smoother, darker skin and tend to be more reddish-colored. Tadpoles are black. The toad has fingers that are not webbed, gold irises with horizontal pupils, ridges running from over the eyes to the nose, and large parotid glands behind each eye. The eye ridge and parotid gland distinguish the cane toad from the otherwise similar-looking southern toad (Bufo terrestris).

Habitat and Distribution

The cane toad is native to the Americas, from southern Texas to southern Peru, the Amazon, Trinidad, and Tobago. Despite its name, the toad isn't actually a marine species. It thrives in grasslands and forests of tropical to semiarid regions.

The cane toad was introduced elsewhere in the world to control agricultural pests, especially beetles. It is now an invasive species throughout the Caribbean, Florida, Japan, Australia, Hawaii, and several other Pacific islands.

Diet

Cane toads are omnivores that identify food using the senses of sight and smell. Unlike most amphibians, they readily eat dead matter. Tadpoles eat algae and detritus in the water. Adults prey upon invertebrates, small rodents, birds, reptiles, bat, and other amphibians. They also eat pet food, human refuse, and plants.

Behavior

Cane toads can survive loss of about half their body water, but they act to conserve water by being active at night and resting in sheltered locations during the day. While they tolerate high tropical temperatures (104–108 °F), they require a minimum temperature no lower than 50–59 °F.

When threatened, the cane toad secretes a milky fluid called bufotoxin through its skin and from its parotid glands. The toad is toxic through all stages of its life cycle, as even the eggs and tadpoles contain bufotoxin. Bufotoxin contains 5-methoxy-N, N-dimethyltryptamine (DMT), which acts as a serotonin agonist to produce hallucinations and a high. It also contains a cardiotoxin that acts much like digitalis from foxglove. Other molecules cause nausea and muscle weakness. The toxin rarely kills humans, but poses a serious threat to wildlife and pets.

Reproduction and Offspring

Cane toads can reproduce year-round if temperatures are high enough. In subtropical regions, breeding occurs during the wet season when temperatures are warm. Females lay strings of 8,000-25,000 black, membrane-covered eggs. Egg hatching depends on temperature. Eggs hatch between 14 hours to a week after laying, but most hatch within 48 hours. Tadpoles are black and have short tails. They develop into juvenile toads (toadlets) within 12 to 60 days. Initially, toadlets are about 0.4 inches in length. The rate of growth is once again temperature dependent, but they reach sexually maturity when they are between 2.8 and 3.9 inches in length. While only around 0.5% of cane toads reach adulthood, those that survive usually live between 10 and 15 years. Cane toads can live up to 35 years in captivity.

Conservation Status

The International Union for Conservation of Nature (IUCN) classifies cane toad conservation status as "least concern." Cane toad populations are abundant and the range of the species is increasing. While there are no significant threats to the species, tadpole numbers are affected by water pollution. Efforts to control cane toads as an invasive species are ongoing.

Cane Toads and Humans

Traditionally, cane toads were "milked" for their toxins for arrow poison and ritual ceremonies. The toads were hunted and eaten, following removal of the skin and parotid glands. More recently, cane toads have been used for pest control, pregnancy tests, leather, lab animals, and pets. Bufotoxin and its derivatives may have applications in treating prostate cancer and for use in cardiac surgery.

Sources

• Crossland, M.R. "Direct and indirect effects of the introduced toad Bufo marinus (Anura: Bufonidae) on populations of native anuran larvae in Australia." Ecography 23(3): 283-290, 2000.
• Easteal, S. "Bufo marinus." Catalogue of American Amphibians and Reptiles 395: 1-4, 1986.
• Freeland, W. J. (1985). "The Need to Control Cane Toads." Search. 16 (7–8): 211–215, 1985.
• Lever, Christopher. The Cane Toad. The history and ecology of a successful colonist. Westbury Publishing. 2001. ISBN 978-1-84103-006-7.
• Solís, Frank; Ibáñez, Roberto, Hammerson, Geoffrey; et al. Rhinella marina. The IUCN Red List of Threatened Species 2009: e.T41065A10382424. doi:10.2305/IUCN.UK.2009-2.RLTS.T41065A10382424.en