Possible Introduction Mechanisms, Movement …...• Cane toads are a great option for high...

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.

If you want more information about

cane toads….

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Any Questions?