Sanibel, Florida (News-Press) -- One of the world's worst invasive non-native species has invaded Sanibel, and it's probably on the island to stay.
a frog-call survey last month, herpetologist Chris Lechowicz of the
Sanibel-Captiva Conservation Foundation heard the slow, low-pitched
breeding call of cane toads.
the sound, Lechowicz found cane toads breeding in a temporary wetland
near Middle Gulf Drive and Fulgar Street - these were the first cane
toads documented on Sanibel.
was very surprised," Lechowicz said. "Cane toads are one of the things
the biologists always said they never wanted to see here."
of Central and South America, cane toads were introduced into Florida
in the 1930s and 1940s to control sugar cane pests.
introductions failed, but the species became established and became a
pest on Florida's southeast coast after the accidental release of about
100 cane toads by a pet dealer in 1957 at Miami International Airport.
don't know what year cane toads reached Southwest Florida, but the
species has been breeding in the area for at least 10 years.
are scattered populations in Southwest Florida, here and there," said
herpetologist Mike Knight, a member of the Florida Invasive Species Task
Force. "It's not like they're widespread, common everywhere."
toads have also become pests in Hawaii, numerous Caribbean islands,
Fiji and Australia - the cane toad is No. 16 on the Global Invasive
Species Database Top 100 World's Worst Invasive Alien Species.
known as marine toads and giant toads, cane toads are typically 4 to 6
inches long but occasionally reach lengths of 8 inches; the native
Southern toad, which is often mistaken for the cane toad, is 2 to 4
"The problem with cane toads is their size," Lechowicz said. "They'll eat anything smaller than them."
That includes native frogs, toads, snakes, lizards, crabs, birds, small mammals and, potentially, sea turtle hatchlings.
Another concern is that cane toads secrete a toxin that can kill predators, including pets.
"They have a tendency to crawl up into dog bowls, which are like
mini-ponds for them," Knight said. "Then Rover comes along, gets
curious, bites the toad and gets a mouth full of poison."
cane toads were first documented on Sanibel in July, the species
probably reached the island several years ago in mulch or plants from
the east coast, Lechowicz said.
But nobody knew the new toads were on the island because they didn't breed, and, therefore, didn't make breeding calls.
don't like to lay eggs where there are fish because fish eat their
tadpoles," Lechowicz said. "They like to lay eggs in shallow, temporary
wetlands, and over the last two years, it hasn't rained much on Sanibel,
so those wetlands weren't there.
on July 4, we started getting a lot of rain, and the temporary wetlands
filled up with water, which allowed the cane toads to breed. It's safe
to say they're established in eight or nine locations."
One surprise was the discovery of thousands of cane toad tadpoles in a 5-foot by 100-foot water-filled puddle on the beach.
SCCF staff spent two days scooping tadpoles out of the puddle with nets.
don't know how many left before we got there," Lechowicz said. "A
single female lays 35,000 eggs, and all those tadpoles could have been
from one toad.
"What I'm worried about is all the places they've been breeding since July 4 that we don't know about."
established cane toad populations is virtually impossible: Adults are
only active at night and only make noise when they're breeding, so
finding individual toads is very difficult, and poisoning breeding areas
to kill tadpoles would kill native amphibians as well as other
a saying among people who deal with exotic species: You don't realize
something's a problem until it's too late," Knight said. "You don't
notice these things, and then suddenly, boom, a big, huge population
makes an appearance and you say, 'Oh, we've got a problem.'"