The cane toad, Rhinella marina, is a large, nonnative amphibian that has become an invasive species across Florida. Their presence poses a serious threat to native wildlife and is particularly dangerous to domestic pets. The toad’s skin glands secrete a potent, milky-white substance known as bufotoxin, which can be fatal to animals that attempt to bite or consume it. The toad has successfully established itself, creating a persistent problem for residents and conservationists.
Identifying the Invasive Species
The cane toad is one of the largest toad species in the world, often reaching lengths between six and nine inches, making it significantly bigger than native toads. Their skin is typically dry and warty, with coloration ranging from reddish-brown to grayish-brown, often with a light-yellow or beige belly. The most distinguishing feature is the presence of large, triangular parotoid glands located behind the eyes. These glands are the source of the powerful bufotoxin.
It is important to differentiate the cane toad from the native Southern Toad (Anaxyrus terrestris). The native Southern Toad is much smaller, rarely exceeding four inches in length as an adult. Unlike the cane toad, the Southern Toad possesses prominent bony ridges or “crests” above its eyes, and its parotoid glands are noticeably smaller and oval-shaped.
The Historical Introduction to Florida
The arrival of the cane toad in Florida was not a single event but a series of introductions spanning several decades. Initial documented introductions occurred in the 1930s and 1940s when the toads were deliberately imported for agricultural use. The goal was to use the toads for biological pest control to consume beetles damaging sugar cane crops. However, this first population did not successfully establish a permanent foothold in the state.
The current, established populations are largely the result of subsequent, accidental, and intentional releases that began in the 1950s and 1960s. A significant event occurred around 1955 when a pet importer reportedly released approximately 100 cane toads near the Miami airport. Additional purposeful releases by pet dealers took place in South Florida throughout the 1960s.
These releases, particularly those linked to the exotic pet trade, provided the critical mass for the species to take hold. The initial areas of establishment were concentrated in South Florida, including regions near Miami and the Everglades. The combination of failed pest control efforts and the pet trade’s contributions solidified the cane toad’s presence as an invasive species.
Current Distribution and Ecological Niche
The cane toad began to spread from its initial introduction points across Florida. The species is now primarily found throughout the central and southern portions of the peninsula. Its established range extends as far north as the Tampa area and generally remains south of the I-4 corridor. Isolated sightings further north are often attributed to escaped or released pets.
The toad’s success is due to its adaptability and preference for human-modified landscapes. They thrive in urban and suburban environments, frequently populating backyards, golf courses, and drainage ditches. These areas provide abundant food sources, such as insects attracted to outdoor lighting, and easy access to water for breeding. The toads are often drawn to outdoor food and water bowls intended for pets, increasing contact with domestic animals.
Cane toad females are highly prolific, capable of laying up to 30,000 eggs in a single clutch. Furthermore, the potent bufotoxin secreted by the adults and present in their eggs and tadpoles deters many native predators, which lack the defenses needed to consume the toxic amphibian. This lack of natural population control, combined with a favorable subtropical climate, allows the cane toad to maintain large numbers in its preferred niche.