What Everyone Ought To Know About Marine Toads
Updated: Feb 19
This month I am writing my first amphibian blog, influenced by going to a recent reptile show, where there were some on sale. In Florida, it is called a marine toad but it also goes by the name of cane toad. I’ve also heard it called the bufo toad, because of the family it was in (Bufo marinus). However, it has subsequently been renamed Rhinella marinus. Ironically, the toad has nothing to do with the sea. Carl Linnaeus described the marine toad in his work Systema Naturae in 1758. He came up with the name based on the illustration done by zoologist Albertus Seba, who mistakenly thought that it lived in both terrestrial and marine habitats. They are also considered the most invasive amphibian in the world. Most commonly heard about for its invasion of Australia (where they are called cane toads), these very large toads were commonly brought into countries to combat insects that ate the plants in the cane fields. It didn’t work. The cane beetles still chomped away on valuable crops and the cane toads learned how to spread out and reproduce in impressive numbers. They are also known as South American cane toad, Giant marine toad, giant toad, and giant neotropical toad.
Marine toads are found naturally in the Rio Grande Valley in extreme southern Texas, Mexico, Central America, and tropical regions of South America. In the United States, they’ve been introduced to the states of Florida and Hawaii - with the same results as Australia. They are also found in the U.S. territories of Puerto Rico, U.S. Virgin Islands, Guam (including Cocos Island), Northern Mariana Islands, and America Samoa. Worldwide they are invasive in Australia, Antigua, Barbados, Cuba, Dominica, Grenada, Carriacou Islands, Guadeloupe, Grand Cayman Island, Haiti, Dominican Republic, Jamaica (including Carbarita Island), Marie Galante, Martinique, Montserrat, Nevis, St. Kitts, St. Lucia, St. Vincent, Tortola, Japan, Taiwan, Papua New Guinea, Philippines, Cook Islands, Micronesia, Fiji Islands, Kiribati, Republic of the Marshall Islands, Solomon Islands, Republic of Palau and Tuvalu. They’ve been introduced (but are not invasive) to Bermuda, Egypt, Mauritius, Thailand, Korea, and Diego Garcia of the Chagos Archipelago. In other words, they get around.
They are the largest species of toad (or frog) in the world and considered one of the top 100 most invasive animals. They are brownish, reddish, olivish with dry skin and a lot of warts - except on the head. A stout body and short legs keep these guys on the ground, where they move in short, quick hops. They have a ridge that goes around each eye and meets above the nose. They can also withstand temperatures between 60° and 100°. During cold and/or dry weather, they enter into a state of hibernation in shallow excavations under ground cover. Rains will bring them back out. Behind each eye is a large gland (called the porotoid) that extends down the side of their bodies in a rough triangle shape. These glands contain a toxin that the toad produces when under stress or threatened. In humans, it can be an be an irritant if it gets on the skin, and burn eyes. To pets, however, it can be deadly. If a pet is suspected to have been poisoned, the first thing to do is look at the color of their gums. If they are bright red, then most likely they
have been poisoned. That is one of the first things a vet will check in order to rule out epilepsy. Other signs are excessive drooling, head-shaking, crying, loss of coordination and possibly convulsions. First aid is taking a hose and running water through the side of their mouth. Make sure the animal is pointed downward so there isn’t any water swallowed. Even if they appear to be responding and start acting normal, take them to a vet as soon as possible. The toads can be around 3.3 pounds and between four and six inches long, with a maximum of nine and a half inches! So, I’ll sum it up this way. They’re big and they are born perpetually looking like a Grumpy Gus or Gussette.
They were introduced in the first half of the 20th century for biological insect control in the lucrative cane fields. Only there’s a problem. An animal can’t be removed from their natural habitat, where they are specifically adapted to live there and find food, export them to other countries and expect them to exhibit the same behavior they had in their native countries. They have to adapt to the new habitats they find themselves in. It rarely works and causes more damage than good. The result of introducing marine toads wasn’t what was hoped. They did absolutely nothing as far as controlling pests that liked to attack cane crops. Outside of their native habitat, they have a degree of protection from predation with their toxin. Especially in countries that don’t have any natural species with a poison-related to them. In Australia, they have caused mass deaths of freshwater crocodiles and monitor lizards. where in their native lands, they do have plenty of predators. In areas where they’re introduced, there aren’t as many animals that can prey on them without being poisoned. They have learned, though, how to eat them. Raccoons, opossum, American crows, red-shoulder hawks (along with other species of birds), and several species of snakes have been observed flipping toads on their backs and eating the toad, completely avoiding the parotoid glands. Well, not the snakes. They swallow them whole.
From the Northern Territory, Australia
Marine toads aren’t the only toad or frog that excrete toxins. In fact, most do. However, their intent isn’t to kill an animal, it merely wants to offer a friendly message. “Hey, I’m a toad and that was just my way of letting you know that I taste really icky. Did you taste me? Yuck, right? I don’t want to hurt you. I just want to bop around here and catch some yummy dinner. If you want to say hi and sniff me, that’s fine. But I get scared when you pick me up in your mouth. If I were a human, I’d pee my pants. But I’m a toad, so I use this yucky stuff instead. I hope you can understand and just not pick me up. Thanks.” That’s what native toads and frogs say. Marine toads look at you and say “If I don’t kill you, I’m going to make you wish I did.” Unless, of course, they are in their native home.
One of the reasons why they are so deadly to many animals is because of the sheer size of the glands. More toxin is released. When threatened, some toads may ooze some slime out, but the usual method is to release it when there is pressure put on the glands, like when picked up by an animal by mouth. They cannot willfully shoot it out at you, but pressure can. They are so toxic that the eggs and tadpoles are to and have been known to kill koi in ornamental ponds. And yes, they are capable of killing people by ingestion. How would bufotoxin be swallowed, you might ask? First off, this isn’t limited to just marine toads, but smaller species as well. It is believed that toad slime has hallucinogenic properties. People catch the toads, squeeze the parotoid glands and lick it directly off the toad. The amount released depends on the pressure placed on the glands, and the dosing is different every time. Cause of death: overdose by toad. Their toxin is considered a schedule one controlled substance and people have been arrested for using it. In 1994, and I’m not making this up, the first man was arrested for “possession of psychedelic toads” - with the intent to lick. The psychedelics were named Hanz, Franz, Peter, and Brian. Read the original New York Times piece here. All joking aside, please don’t lick toads and frogs - or milk them with the intent to ingest them. They can cause a person to become seriously ill, or die - many times the hallucinogen doesn’t take effect or the toad just doesn’t have a huge amount in their toxins...but lots of other nasty chemicals that can cause cardiac arrest.
Cane toads might have failed to eat enough pests to control the damage done to sugarcane crops, but they do eat them. In fact, they will eat anything they can swallow that is low on the ground and happens to walk into the path of a marine toad. Or anything the marine toad passes, say feces. There’s the usual array of insects, but they also will eat small mammals, reptiles, other amphibians, and birds. Unlike other toads, marine toads don’t depend entirely on seeing movement. They can also smell out food, and in areas where they are, it isn’t surprising to find them eating dog or cat food left out for pets. They are found mostly in urbanized areas like lawns, schoolyards, sports fields, golf courses, agricultural land, and any other habitats modified by humans. They are rarely found in less settled/natural areas, though there have been calls heard in Biscayne and Everglades National Parks (coincidentally, little toad size phone booths were found. They tried calling with cell phones but couldn’t get a signal). Because of this, the marine toad is not a known threat to natural ecosystems. That doesn’t mean that they don’t cause harm. Wherever marine toads invade, it has been noticed that the southern toad disappears or is rarely seen. This could be due to competition - with their voracious appetites, it wouldn’t be a surprise if a large population of marine toads depletes prey animals that native animals also depend on.
There are a number of precautions that can be taken to keep them out of yards. First, don’t leave out dishes full of food continuously. If pets must be fed outside, then it should be at specific times (animals learn when it’s time to eat) and that they are supervised while they eat and any food left over be taken back inside. Also, take in water dishes, too. The toads consider them to be luxurious bathtubs in which to have a relaxing and pleasant soak. When dogs are out at dawn, dusk, or night, they should be on a leash or accompanied by their owners. If the dogs are likely to go after things that move, like terriers, keep them on a short lead. Better yet, owners should check into training dogs to not pick up any animal. Don’t turn on any bright lights at night that attract insects. They will congregate around bright lights for that reason. If they must be used, try motion sensor lights that turn on when movement is detected. I used to horse watch, and at night her barn had a powerful light with scores of frogs on the walls and toads (not marine toads) on the ground. Clean up any debris piles that the toads (or rodents and snakes) can spend their days in. Block openings that they can get in. Under air conditioner units, buildings, compost heaps, and under decks. Check ornamental ponds and remove eggs and tadpoles.
This next one is not something I could do, and my first recommendation would be to call a trapper in, but many biologists urge people to humanely euthanize invasive toad species. There are a couple of ways. The first would be to anesthetize them using 20% benzocaine - readily available at any drug store in medications for toothaches and sunburns. Wait for thirty minutes for them to fall into a deep sleep, and then put them in the freezer for at the very least 48 hours but probably 72 would be better, to make sure they are dead. The other would be to place them in the fridge for about an hour, causing the same reaction as the benzocaine, where they can then be transferred to the freezer. Again, this is not something I could do and I don’t advocate people killing them on their own. I would much rather call in a trapper, where they probably have a better way to dispatch them. I do support removing invasive animals, though. For the sake of the native wildlife, ecosystem, and the invasive animals themselves. Again, my preference is to use professionals and those that have been trained by the state. There are three other toads that are native to Florida (southern toad, oak toad, and eastern spadefoot toad) that can be mistaken for the marine toad if the person is not familiar with differences in species. While the marine toad is very large compared to the natives (max for them is three inches) but juvenile marine toads are not as large and can be within the size range for native species.
Mating season is generally all year long. Males sit in still or slow moving water and obnoxiously call out for females. Males will fertilize the eggs of multiple females, and females will have her eggs multiplied by several males. And is it any wonder? She lays anywhere between 8,000 to 30,000 eggs in strings of gelatinous material that can be over 60 feet long! They hatch into tadpoles in about a week that stay in schools together. They are black with a silvery white belly. They begin to metamorphose in around 60 days. At no time during their life cycle are they not toxic. There is high predation, regardless, of eggs, tadpoles, and toadlets. Only around .5% make it to adulthood. It’s not much, but that is 150 toads that will reach maturity if 30,000 eggs are laid.
Tadpoles feeding during metamorphosis
While habitat destruction and climate change are major factors in how people are adversely affecting the world, another one is the release of animals into ecologies in which they don’t belong. In healthy ecosystems,, predators ensure their prey’s survival by picking off the old, sick, and young. Thus, ensuring that the healthiest animals can move forward to breed. When an invasive animal that breeds quickly and in high numbers with voracious appetites takes over that ecosystem, it can destroy it, even to the detriment of the invasive animal. Unsustainable populations will eat all available food, not only putting their existence in jeopardy but the existence of the animals that belong and the delicate balance that keeps it healthy. Humans are constantly trying to fix the problems we created usually at the death of the animals that are innocent in all this. The goal now is to reach manageable populations. There really is no means to eradicate all invasives, and it has only been achieved on islands, like those in New Zealand, and that took years for each island. I hope that now that we know the horrible effects, we can educate one another in the harm that can be done.
Click on the arrow on the right to see some more pictures of toads!!