Update on the Recent Introduction of the Giant Toad (Rhinella marina) on Sanibel Island, FL Chris Lechowicz Director-Wildlife Habitat Management Program/Herpetologist Sanibel-Captiva Conservation Foundation
Update on the Recent Introduction of the
Giant Toad (Rhinella marina) on Sanibel Island, FL
Chris Lechowicz
Director-Wildlife Habitat Management Program/Herpetologist
Sanibel-Captiva Conservation Foundation
Giant Toad (Rhinella marina)
• Also called the cane toad, marine toad, Bufo toad, faux
toad.
• Previously Bufo marinus
• Native to Central America, South
America, Mexico, and south Texas.
• A true toad (Family Bufonidae) belonging to a group of
Neotropical toads (beaked toads = Rhinella).
• Largest Bufonid toad (up to 5.8 lb), but not the largest
Anuran (frog) in the world.
Notable Facts
• They have very large paired parotoid glands containing
Bufotoxin that is oozed out when harassed.
• This milky toxin has killed household pets (dogs, cats)
and numerous wildlife species when ingested.
• There has been documented human fatalities from “toad-
licking” and ingestion.
• Eggs/larvae are toxic to wildlife.
• Highly nocturnal
Range
Rhinella marina Purple = native range
Red = introduction
Prey and Predators
• They consume invertebrates, small rodents, birds,
amphibians, reptiles , and plants.
• They will eat non-living prey (small dead animals, dog
and food, feces).
• The are preyed on in their natural range by caimans (C.
latirostris), certain species of fish, Possums (Didelphis
species), meat ants, banded cat-eyed snake (Leptodeira
annulata), and some species of ibis.
• They can lay up to ~30,000 eggs a year.
Introduction History
• Barbados and Martinique -Caribbean (early 1840’s)
• Jamaica, rat control (1844) , not successful
• Puerto Rico, beetles/sugar cane (1920, 1923) successful
• Australia, Papua New Guinea, Philippines, Japan, Fiji,
Hawaii* , Florida (1930’s)
Florida History Range
• Introduced into Florida in 1936 and 1944 (Agricultural
Experimental Station of the University of Florida) to control sugar
cane pests (white grubs, Scarab beetle larvae).
• Another introduction occurred in 1957 at the Miami Airport
from an importer (accidental). Other intentional introductions in
1963 and 1964 resulted in other established populations.
• They also occur in isolated populations on the west coast of
Florida likely from small accidental and intentional introductions.
Florida Herp Atlas (2011)
Similar Local Species
Southern toad (Anaxyrus terrestris)
• Less proportional parotoid glands
as compared to R. marina.
• Up to 92 mm (3.8 in) in length
Oak toad (Anaxyrus quercicus)
• Large parotoid glands
proportional to body size.
• Up to 33 mm (1.3 in) in length
Egg and Tadpole Identification
Sanibel Discovery
•
The Sanibel route is conducted by a collaboration of biologists from
the J. N. “Ding” Darling National Wildlife Refuge and SCCF.
Cane toads were first heard during a Frog Watch survey on July 18,
2013 on the east end of Sanibel.
Runnels
August 2013
August 2013
August 2013
August 2013
September 2014
September 2014
September 2014
Sanibel Control Efforts
• SCCF is the data and cane toad depository organization on Sanibel Island.
• All collected cane toads are euthanized at C.R.O.W.
• Beach runnels are monitored on the beach after heavy rainfall.
• SCCF gives frequent educational lectures to the public about the cane toad problem.
Bucket Traps
• SCCF and Refuge biologists have been
experimenting with Australian designed bucket
traps on conservation lands for presence/absence.
Gut Content
• Dissected toads had a variety of plant and animal species in
their gut.
• The most abundant faunal group represented were
invertebrates (Blattodea, Coleoptera, Lepidoptera,
Gastropoda), followed by Squamata-Lacertilia (Anolis)
• Sea grape (Coccoloba uvifera) berries were also found in the
gut of two toads.
• Cane toads are a great option for high school/college
dissections instead of native bull frogs (L. catesbeianus) or
green frogs (L. clamitans) from biological supply houses.
7/19/13
9/13/13
12/5/14
2/19/16
First Mass Breeding Occurrences on
Sanibel by Year
2013 2014 2015 2016
July September March January
These mass breeding occurrences coincide with the
first major rain events of the year and night
temperatures higher than 17.2°C (63°F).
Conclusions
• R. marina was first documented on Sanibel in
July 2013 in a localized area. Their range now
occupies ~62% of the island.
• Toads likely arrived to Sanibel several years
prior to July 2013 and waited for the proper
water levels in ephemeral areas to induce mass
breeding which triggered detection.
Conclusions
• Current capture patterns, along the beach, suggest that their habitat preference on Sanibel is open canopy landscapes bordered by human developments.
• Rapid expansion across the island began after the 2013 summer rains.
• The breeding season is dependent upon rainfall (increasing water levels) and night temps above 17.2° C (63° F) and NOT a specific time of year.
Conclusions
• Continual education of residents and visitors is essential to document new localities and to reduce pet (dog and cat) interactions.
• Total eradication is highly unlikely, but removal of adults can benefit local areas by reducing reproduction.
• Native species interactions (fatalities) with R. marina need to be documented.
Conclusions
• Increased resident participation in eradication
efforts is essential.
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