During the monthly frog call surveys conducted by the J.N. "Ding" Darling National Wildlife Refuge and Sanibel-Captiva Conservation Foundation (SCCF), a population of giant toads (Rhinella marinus), also known as cane toads or marine toads, were discovered on July 17 breeding in a temporary wetland near Middle Gulf Drive and Fulgar Street.
More cane toads have been found at four other locations on Sanibel since, with possible sightings at two more.
Like most other invasive amphibians and reptiles on the island, they did not migrate here by themselves. More likely, they were accidentally brought here in mulch, pine straw, sod, plants, or even tadpoles hiding in a small pool of water on any object transported to the island.
Courtesy of SCCF
Cane Toad (left) and Southern Toad (right) with the parotoid gland, the source of the Cane Toad’s toxin, indicated on both. The gland is larger on the Cane Toad.
This species poses a serious threat to wildlife on Sanibel, as well as domestic pets. The large glands behind the eyes and above the shoulders (parotoid glands) produce a toxin that is both irritating and deadly to smaller wildlife. When a predator grabs a giant toad in their mouth, the toad inflates its body and the toxin oozes out of the parotoid glands into the mouth of the predator. It is well documented that the poison has killed pet dogs in south Florida.
The literature and conversations with veterinarians and pet owners indicate it is a horrific death for the animal. There have even been human fatalities from this species from toad-licking. The tadpoles are also toxic, which can lead to fatalities in many animals that consume them. Special care should be taken to prevent dogs, cats, etc. from biting or grasping these toads in their mouths.
These are very large toads, reaching up to 5.5 inches in length and possibly near five pounds. They are voracious eaters. They will eat insects, snakes, baby turtles (including small sea turtles, gopher tortoises, box turtles, etc), lizards, small mammals, and birds. They will even eat pet food or any other kind of food left outside. It is highly unique for a frog to eat nonliving food. These toads are attracted to bright lights at night because they attract insects.
Giant toads are South American in origin. They were brought to Australia in the 1930s to control cane grubs in sugar cane fields. They did not control cane grubs and started eating smaller vertebrates. They have spread throughout northeastern Australia and are still a serious threat. They were released in sugar cane fields in Florida to control a larval form of a beetle as well, hence the name "cane toad." Just like in Australia, they escaped from the area and became established.
Also, there is a record of approximately 100 being accidentally released in the 1950s in Miami by a pet dealer.
The best case scenario is that this is a small isolated population. The removal of this species from Sanibel, if possible, is crucial for delicate species. SCCF needs your help in identifying any other places where these toads may be present. Sanibel cannot afford to have this species spread throughout the island.
Keep in mind that there is a similar native amphibian found on Sanibel. The southern toad (Anaxyrus terrestris) is also a true toad (Family Bufonidae). Southern toads are smaller than giant toads (averaging around three inches in length).
Young giant toads and adult southern toads are similar in appearance and size. A major difference between the two toads is the size of the parotoid glands. Southern toads have small parotoid glands as opposed to the very large glands on giant toads. Southern toads also have "toxin" (more of an irritant) in their parotoid glands. It is nowhere near as potent as cane toads.
Many animals eat these toads, but that toxin is a deterrent to certain wildlife species. If you hold a southern toad and they are threatened, they will ooze the toxin. If you get it in your eyes, they will burn and water for 20-30 minutes.
According to SCCF, you can find a recording of the cane toad's mating call at SCCF's Nature Center or online at graptemys.com/giant_toad.wav
There are informal "tank talk" sessions on Friday, July 26; Monday, July 29; and Wednesday, July 31 at 10 a.m., but the toads will be on view during regular Nature Center hours, 8:30 a.m.-3 p.m. Monday through Friday.
Anyone who sees or hears a giant toad on Sanibel or Captiva is asked to report it to SCCF's wildlife habitat management office at 239-472-3984. First, and foremost, take a picture of the toad, if possible, so it can be verified.