Possible Introduction Mechanisms, Movement Patterns, and Control Efforts 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

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.

Current uses for Cane Toads

• Educational purposes (the dangers of exotic species)

• Pregnancy tests

• Leather goods

• Pet trade

• Eaten in Peru (after removal of the skin)

• Poison darts (South America)

World Range

Rhinella marina Purple = native range Red = exotic range 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.

Similar Local Species

Southern toad (Anaxyrus terrestris) Oak toad (Anaxyrus quercicus)

• Less proportional parotoid glands • Large parotoid glands as compared to R. marina. proportional to body size.

• Up to 92 mm (3.8 in) in length • Up to 33 mm (1.3 in) in length

Egg and Tadpole Identification

Amphibians & Reptiles of Sanibel & Captiva Islands, Florida • 9 Frogs and toads (3 exotic) • 17 Turtles (1 exotic) • 2 Crocodilians • 16 Lizards (11 exotic) • 17 Snakes (1 exotic)

- 61 total amphibian and reptile species present - 9 amphibian species present (33% exotic) - 52 reptile species present (25% exotic)

• 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.

Sanibel Invasion

• Ten adult cane toads were removed from the first known breeding pool and have not been seen there since. However, the were also found breeding in small numbers in an adjacent golf course the same week.

• For the next 10 days, SCCF/COS/DING conducted night surveys around that area to try to detect more breeding sites.

• Several press releases on the island resulted in a strong resident interest in eradication efforts (volunteers).

Possible Introduction Methods

• Intentional or accidental release from captive animals?

• Accidental introduction from shipments of plants, mulch, sod, dirt , etc. containing cane toads (eggs/tadpoles/juveniles/adults). Runnels

August 2013 August 2013 August 2013 August 2013 Beachgoers/instant volunteers SCCF SCCF Sea Turtle Biologist Shorebird Technician

SCCF Biology Intern

SCCF Snowy Plover Intern SCCF Biology Intern SCCF Marine Lab Research Assistant August 2013 September 2014 September 2014 September 2014 September 2014 September 2014 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 Sanibel Discovery

• R. marina moved approximately 6.6 km (4.1 miles) in 2013 and up to 9.1 km (5.7 miles) in 2014 from the first known breeding pond.

• The dispersal pattern appears to be following the beach near residential areas.

• In 2013-2014, they were documented successfully reproducing in beach runnels approx. 8.2 m (27 ft) from the Gulf of Mexico (runnel water = 4 ppt).

• There has been outstanding resident participation in control efforts.

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.

• Additional frog call surveys have been added.

• Runnel monitoring on the beach during the wet season.

• Frequent educational lectures are given at SCCF informing the public about the cane toad problem.

Summary • R. marina was first documented on Sanibel in July 2013 in a very small area and their range now covers ~35% 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.

• Current capture patterns, along the beach, suggest that their habitat preference on Sanibel is less densely vegetated landscapes bordered by human developments.

• Eradication efforts are limited to adult removal in hopes of reducing the number of reproducing individuals, as well as runnel draining. Summary • Success of control efforts on the island is dependent upon resident participation.

Other Resources

Book Book Netflix stream A special thanks to…

J.N. “Ding” Darling National Wildlife Refuge, The City of Sanibel, C.R.O.W., Florida Museum of Natural History, Calusa Herpetological Society, Frog Watch, numerous residents, visitors, and condo associations on Sanibel Island. Any Questions?