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

29 thoughts on “The marine toad

      1. I don’t think it’s true with turtles. I’ve had one for over 20 years that hasn’t grown past 8″. She’ll molt her shell once a year or so, but she’s the same size.

        1. I am thinking that turtles and tortoises do not molt. But they do add a kind of growth ring to the borders of their scutes as they grow.

  1. We are right in the middle of the summer rains where I live (Western Ethiopia). Most days, around six p.m. the thunder starts to grumble, the rain begins to patter, and every other sound – even the caterwauling of the priests which is broadcast through gigantic loudspeakers from every church – is temporarily drowned out as the frogs start their calling. Then the downpour begins, drumming on the tin roof, suppressing any other noise.

    Last night, as I was reading by candlelight (the power goes off as soon as the storm starts), I caught a movement in my peripheral vision. I got a torch and spotted a minute frog, I would estimate about half a centimetre long, shuffling in small hops across the floor. When I moved to get a camera on it, it executed a hop of about a metre, i.e. 200 times its body length. I will see if I can do better with the camera if I see it again, but I presume it had not long grown out of its tadpole stage. Noisy as they are, it is remarkably difficult to spot the adults, as you can’t tell where the sound is coming from.

  2. I was curious about why it is also known as the Marine toad, and have learned that is because an early zoologist thought it could occupy marine environments.

  3. That brings to mind, the only noise that comes close to the frogs and toads on the lake or pond is the very noisy cicada.

    1. We have a plethora of very noisy cicadas here in central Texas, including the Giant Cicada (Quesada gigas), which sounds like a piercing train whistle. I enjoy hearing the calls of the more low-key cicadas when I’m outdoors, though.

  4. I’ve no malice towards the toads themselves, they’re just “toading” but I abhor the decision to introduce this species to South Florida. In addition to the negative effects on native fauna, I’ve personally lost 2 dogs to this species. Toad poisoning is an ugly way to watch a beloved pet die.

    1. I wonder if you could rain a dog to avoid cane toads by giving it less dangerous toads to play with. I think a dog who’d gotten a taste of a more common toad might avoid all toads. My cat developed a fear of toads after the second one she caught. Getting sick twice was enough to put her off them forever.

      Not sure it would work, but I’d hate to think you might have to go through the loss of another dog.

        1. The first time happened because my sister and I did not know not to leave dog food outside in areas where the toads live. We were still pretty young at this point. They’ll get into the dog’s bowl and the dog will, of course, attack something it thinks is stealing its food.
          The second time was really awful. I let my dog out unattended in the backyard for no more than 5 minutes. She must have picked up the toad almost immediately. By the time I saw her in the back yard, she was already seizing. I knew what was happening and I knew it was almost certainly too late.

      1. There are reputedly more humane ways to train d*gs, but that one would probably work too.

        There have been a number of studies involving training native Australian fauna of relatively little brain (e.g. quolls, goannas) to avoid eating toads, with some success. But even if all potential predators of the things could be trained (or evolved) not to eat a toad big enough to kill them, or how to eat only the less toxic parts, they’d still be an ecological disaster (large net loss of biodiversity) here because of their competition for food with natives and direct predation on smaller vertebrates.

  5. I haven’t read Zug’s book, but would like to know if Jerry prefers it to Christopher Lever’s The Cane Toad. I live in Trinidad, where it is native, and lots of dogs here (mine and those of friends) know that dogs here quickly learn to leave them alone. In fact, mine, and my friend’s, have what we call a “toad bark”. It’s a type of barking that they do when they find one. They bark at it until we come to remove it from the yard.

  6. I remember seeing these by the hundreds on Maui. We were told they were poisonous and to stay away. I thought maybe they were that psychedelic toad (don’t know what species) and they just didn’t want anybody licking them and getting high. From this post, I realize they were indeed poisonous.

    Does Toady survive outside during the Wisconsin winter, or do you take her inside?

  7. In the wild these are rather impressive animals. I saw them frequently in Nicaragua rather fearlessly sitting by the side of the trail. No doubt contemplating ecological apocalypse.

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