The marine toad

September 3, 2015 • 9:00 am

by Greg Mayer

Jerry had us spot the toad a few posts ago (I earlier posted an easier ‘spot the frog‘), and in the comments some readers mentioned the marine toad, Bufo (Rhinella) marinus, also known as the cane toad (especially in Australia) or the giant toad. This species, native from south Texas to central Brazil, has been widely introduced in the West Indies (including Bermuda), Florida, Australia, and the Pacific islands. They were introduced primarily as a way to control a beetle which attacked sugar cane; the toads were not very good at this, and have had negative effects on more desirable faunal elements in some places.

Adult female Bufo (Rhinella) marinus, in 2012; origianlly collected on Bermuda, 1999.
Adult female Bufo (Rhinella) marinus, in 2012 in my back yard (Racine, Wisconsin); originally collected on Bermuda, 1999.

The above is my pet female, collected for me during a visit to Bermuda in 1999 by Bermuda’s foremost naturalist and conservationist, David Wingate. He has succeeded in eliminating the toads from Nonsuch Island, a preserve where the restoration of Bermuda’s indigenous fauna and flora is being promoted, with considerable success. She is fairly large, being 165 mm snout-vent length; unfortunately, I did not measure her when I first got her, but she was adult-sized at the time. The largest one I have ever found myself was a 178 mm one in Nicaragua. They get up to around 250 mm; the largest ones are said to be from the Guianas. A rather large preserved individual at the Museum of Comparative Zoology is about 230 mm long, and has long resided in a large Agassiz jar on the coffee table in the herpetology department.

In addition to being large, she’s getting old. I had thought she must be a record, but found that ages up to 25 years have been reported. “Toady” must be at least 17, perhaps a bit more, so she’s got a few years to go. Her only sign of aging is a cataract-like opacity in her right eye, which does not seem to have interfered with her ability to spot prey.

Notice the very large parotoid gland behind her ear; these secrete a milky poison when the toad is stressed, and I have been told that d*gs, not being terribly bright, have been sickened and even killed by attempting to ingest the toads. In South America, carnivorous mammals are said to flip the toads over, and eat them from the belly side, where the skin does not contain toxins (or at least not as much). When being defensive, Toady angles her back toward the unwanted stimulus. The best overall guide to the biology of these toads is still “The Marine Toad, Bufo marinus: a natural history resume of native populations” by my friend and mentor, George Zug, and his wife Pat.

Easteal, S. 1981. The history of introductions of Bufo marinus (Amphibia: Anura); a natural experiment in evolution. Biological Journal of the Linnean Society 16:93-113. abstract

Slade, R.W. and C. Moritz. 1988. Phylogeography of Bufo marinus from its natural and introduced ranges. Proceedings of the Royal Society of London B 265:769-777.  pdf

Wingate, D.B. 2011. The successful elimination of Cane toads, Bufo marinus, from an island with breeding habitat off Bermuda. Biological Invasions 13:1487-1492.  abstract

Zug, G.R. and P. B. Zug. 1979. The marine toad, Bufo marinus: a natural history resume of native populations. Smithsonian Contributions to Zoology 284, 58 pp.   pdf