Cane Toad, Bufo marinus

The Cane Toad (Bufo marinus) known also as the Giant Neotropical Toad or the Marine Toad, is a large and terrestrial true toad which is endemic to Central and South America, but has been introduced to various islands throughout Oceania and the Caribbean. It’s a member of the subgenus Rhinella of the genus Bufo, which includes many different true toad species that are found throughout Central and South America. It is a productive breeder; the females lay single-clump spawns with thousands of eggs. Its reproductive success is partially because of opportunistic feeding: it has a diet, strange among anurans, of both dead and living matter. The adults average 3.9 to 5.9 inches long; the largest documented specimen weighed 5.8 pounds with a length of 15 inches from snout to vent.

This is an old species. A fossil toad from the La Venta fauna of the late Miocene of Columbia is indistinguishable from the modern cane toads from northern South America. It was discovered in a floodplain deposit, which proposes the B. marinus habitat preferences have always been for open areas.

This toad has poison glands, and the tadpoles are highly toxic to most animals if they’re ingested. Due to its voracious appetite, the cane toad has been introduced to many regions of the Pacific and the Caribbean islands as a method of agricultural pest control. The species gets its common name from its use against the cane beetle. The cane toad is now considered a pest and an invasive species in many of its introduced regions; of particular concern is its toxic skin, which kills many animals, whether native predators or otherwise, when ingested.

Within Australia, the adults may be confused with large native frogs from the genera Limnodynastes, Cyclorana and Mixophyes. These species can be distinguished from the cane toad by the absence of large paratoid glands located behind their eyes and the lack of a ridge between its nostril and its eye. Within the United States, this toad closely resembles numerous bufonid species. Particularly, it could be confused with the southern toad, which can be distinguished by the presence of two bulbs in the front of the parotoid glands.

Being a very large toad, the females are considerably longer than the males, reaching a mean length of 3.9 to 5.9 inches. Some larger toads show a tendency to be found in areas of lower population density. Their life expectancy is ten to fifteen years in the wild but they can live considerably longer in captivity, with one specimen reportedly surviving for 35 years.

The skin on this toad is dry and warty. It has distinct ridges above the eyes, which run down the snout. Individual cane toads can be grey, red brown, olive brown, or yellowish, with varying patterns. A large parotoid gland lies behind each of the eyes. The ventral surface is cream-colored and may have blotches in shades of black or brown. The pupils are horizontal and the irises are a golden color. The toes have fleshy webbing at their base, and the fingers have no webbing.

A juvenile cane toad is much smaller than the adult toad at 2 to 3.9 inches long. Usually, they have smooth and dark colored skin, although some specimens have a red wash. The juveniles lack the adult’s large parotoid glands, so they’re usually less poisonous. The tadpoles are small and consistently black, and are bottom-dwellers, showing a tendency to form schools. These tadpoles range from .39 to .98 inches long.

The cane toad is entirely terrestrial, only venturing to fresh water for breeding. The tadpoles have been found to tolerate salt concentrations that are equivalent to at most fifteen percent that of seawater. It inhabits open grassland and woodland, and has displayed a “distinct preference” for areas that have been modified by humans, such as gardens and ditches for drainage. In their native habitats, the toads can be found in subtropical forests, although dense foliation tends to restrict their dispersal.

It begins life as an egg, which is laid as part of long strings of jelly within water. A female lays 8,000 to 25,000 eggs at once and the string can stretch up to 66 feet long. The black eggs are covered by a membrane and their diameter is about .067 to .079 inches. The rate at which an egg evolves into a tadpole is dependent on the temperature; the pace of development increases with the temperature. They usually hatch within 48 hours, but the period can vary from 14 hours up to almost a week. This process typically involves thousands of tadpoles. It takes between 12 and 60 days for the tadpoles to develop into toadlets, with four weeks being the usual. Similarly to their adult counterparts, eggs and tadpoles are toxic to many animals.

When they emerge, the toadlets are usually about .39 to .43 inches long, and grow rapidly. The rate of growth typically slows down once the toads reach sexual maturity. This rapid growth is significant for their survival; in the period between metamorphosis and sub adulthood, the young toads lose the toxicity that protected them as eggs and tadpoles, but have yet to fully develop the parotoid glands that produce the bufotoxin. Because they lack this key defense, only .5 percent of cane toads are estimated to reach adulthood.

The majority of frogs identify their prey by movement, and vision appears to be the key method by which the toad detects their prey; however, the cane toad can also locate food utilizing its sense of smell. They consume a variety of material; in addition to the normal prey of small rodents, other amphibians, birds, reptiles and a range of invertebrates, they also eat plants, dog food, and household refuse.

Image Caption: Cane Toad female, feral in the Tanamai desert, Northern Teritory, Australia. Credit: Benjamint444/Wikipedia